"This process can be done repeatedly to establish a circular monomer-polymer-monomer cycle," says study author Eugene Chen, a professor of chemistry at Colorado State University.
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Building one of these conductive polymers requires precisely controlling each monomer.
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These are molecules built from a single regular repeating unit, called a monomer.
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They could then convert it back to its monomer and polymerize it again.
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A monomer of Teflon, a nonstick synthetic resin (top), and a chain of monomers (bottom).
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The hitch: The monomer starting product is currently too expensive to be used on an industrial scale.
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The plant makes a vinyl chloride monomer, also known as chloroethene, an industrial chemical used to produce plastic piping.
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Chen says they need to develop new routes to make the monomer so it could be more economically competitive.
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They used a small amount of catalyst to convert a monomer into a polymer that has properties of common plastics.
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Acrylic powder hardens in seconds after being mixed with liquid monomer—a process not dissimilar to the one Leikeli is articulating on the album.
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The plant produces some 900 tons a day of vinyl chloride monomer, also known as chloroethene, an industrial chemical used to produce plastic piping.
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Specifically, adding a GTP (guanosine triphosphate) monomer to a microtubule corresponds to a car parking after the right-most car in the idealized lot.
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But their special electrical properties come from a dangly bit hanging off of each monomer that has an extra, unbound electron, called a free radical.
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However, that process currently requires too much energy and isn't selective enough to recover the valuable monomer, chemist Jeannette Garcia from IBM Research tells Axios.
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Not seen in the New York Times Crossword since 1972, a MONOMER is a single molecule that can be joined by other molecules to make something larger.
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In February, a fire killed a worker at the PMV plant, which makes vinyl chloride monomer, also known as chloroethene, an industrial chemical used to produce plastic piping.
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The resulting strains created omega-3 fatty acids and even a chemical monomer that could be fed into a 3-D print to create plastic objects like a wrench.
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The investigation into Ethylene Propylene Diene Monomer rubber (EPDM) should be finished by June 19, 2020 but can be extended further under special circumstances, the ministry said in a statement.
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Saudi Basic Industries Corp (SABIC) shelved plans in 2014 to expand its Sadaf plant in Jubail which was due to have added production of polyols, propylene oxide and styrene monomer.
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The investigation into ethylene propylene diene monomer rubber (EPDM) should be finished by June 19, 2020, but can be extended further under special circumstances, the ministry said in a statement.
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The Saudi firm, one of the world's largest petrochemicals groups, added in a bourse filing that it had also begun trial operations at the ethylene propylene diene monomer unit of the KEMYA complex on Friday.
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The financial impact of the start of commercial operations at the polybutadiene unit would be reflected in its fourth-quarter earnings, while the ethylene propylene diene monomer business would likely reach full capacity in the first quarter of 2017.
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To create smart circuitry using RVD, normal fabric or thread is placed in a vacuum chamber in which two chemicals, an oxidant and a chemical building block called a monomer are vaporized and react to form a thin, conductive polymer coating right on the cloth.
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F_1 = the mole fraction of monomer added instantaneously to copolymer that is a monomer 1. f_1 = the instantaneous mole fraction of monomer mix that is monomer 1.
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RAFT single unit monomer insertion (SUMI) is recently developed as an emerging technology for precise control of monomer sequence.
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MDP Monomer (10-Methacryloyloxydecyl dihydrogen phosphate) is used for dental adhesive materials. The phosphate monomer was developed by Kuraray co.
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For instance, C−I cleavage is possible electrochemical reduction. Crystal structures of monomer (2) are disordered materials of varying composition and connectivity. Hosts (3–7) were investigated for their molecular packing, primarily by studying co-crystals of monomer (2) and respective host. Both (3) and (4) pre- organized monomer (2), but steric crowding around the iodines prevented successful topological polymerization of the monomer.
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PVA is a vinyl polymer. Polyvinyl acetate is prepared by the polymerization of vinyl acetate monomer (free radical vinyl polymerization of the monomer vinyl acetate).
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In this case, each monomer prefers reaction with itself and the other monomer equally. This causes equal rates of consumption for copolymer formation and leads to random copolymerization.
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Since each monomer in this copolymer has the same reactive group on both ends, the direction of the amide bond reverses between each monomer, unlike natural polyamide proteins, which have overall directionality: C terminal → N terminal. In the second case (so called AA), the repeating unit corresponds to the single monomer.
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Human EPO is known to exist as a soluble monomer.
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In solution, this dimer quickly reverts to the blue monomer.
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Both DCPD and Grubbs' catalyst are imbedded in an epoxy resin. The monomer on its own is relatively unreactive and polymerization does not take place. When a microcrack reaches both the capsule containing DCPD and the catalyst, the monomer is released from the core–shell microcapsule and comes in contact with exposed catalyst, upon which the monomer undergoes ring opening metathesis polymerization (ROMP). The metathesis reaction of the monomer involves the severance of the two double bonds in favor of new bonds.
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Here, we'll take the concept of obstruction to encompass not only monomer-monomer interactions, but also constraints that arise from the presence of dust and boundary conditions such as walls or other physical obstructions.
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NVA is an amphipathic monomer. It was introduced and compounded in the U.S. in 1967. Today, it is recognized as a monomer that does polymerize; however, Showa Denko K.K. succeeded in its industrialization in 1997.
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In gradient copolymers the monomer composition changes gradually along the chain.
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Methyl methacrylate is the monomer from which many polymethacrylates are made.
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Domains 1 and 3 are similar in structure as they both consist of helix-turn-helix motifs. Domain 1 of the monomer contains the amino terminus. Domain 2 contains one small beta sheet, nine alpha helices, and the carboxyl terminus. Three of the nine alpha helices on one monomer are engaged mainly in hydrophobic interactions with another monomer to form a dimer.
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Cyclopentadiene monomer in an ice bath Cyclopentadiene production is usually not distinguished from dicyclopentadiene since they interconvert. They are obtained from coal tar (about 10–20 g/tonne) and by steam cracking of naphtha (about 14 kg/tonne). To obtain cyclopentadiene monomer, commercial dicyclopentadiene is cracked by heating to around 180 °C. The monomer is collected by distillation, and used soon thereafter.
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A semi-empirical method for the prediction of reactivity ratios is called the Q-e scheme which was proposed by Alfrey and Price in 1947. This involves using two parameters for each monomer, Q and e . The reaction of M_1 radical with M_2 monomer is written as k_{12} = P_1Q_2exp(-e_1e_2) while the reaction of M_1 radical with M_1 monomer is written as k_{11} = P_1Q_1exp(-e_1e_1) Where Q is the measure of reactivity of monomer via resonance stabilization, and e is the measure of polarity of monomer (molecule or radical) via the effect of functional groups on vinyl groups. Using these definitions, r_1 and r_2 can be found by the ratio of the terms.
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Hydrogenation of DMT affords the diol cyclohexanedimethanol, which is a useful monomer.
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Furthermore, WNK1 and WNK4 may interact to form heterodimers that inhibit WNK1 function. WNK4 release from the heterodimer allows WNK1 monomer to bind another WNK1 monomer to promote activation. WNK1 function can also be inhibited if WNK1 is degraded.
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The protein can function as a monomer or as a disulfide-linked homodimer.
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Once integrated in the OMM, BNIP3 exists as an inactive monomer until activated.
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Initiation can also involve the transfer of an electron from the alkali metal to the monomer to form an anion- radical. Initiation occurs on the surface of the metal, with the reversible transfer of an electron to the adsorbed monomer.
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In some cases, the monomer has a physical interpretation, such as an amino acid in a polypeptide. In other cases, a monomer is simply a segment of the polymer that can be modeled as behaving as a discrete, freely jointed unit. If so, l is the Kuhn length. For example, chromatin is modeled as a polymer in which each monomer is a segment approximately 14-46 kbp in length.
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Acemannan's monomer is mannoacetate linked by β-1,4-glycosidic bonds. This polymer is hydrophilic.
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In statistical copolymers the sequence of monomer residues follows a statistical rule. If the probability of finding a given type monomer residue at a particular point in the chain is equal to the mole fraction of that monomer residue in the chain, then the polymer may be referred to as a truly random copolymerPainter P. C. and Coleman M. M., Fundamentals of Polymer Science, CRC Press, 1997, p 14. (structure 3). Statistical copolymers are dictated by the reaction kinetics of the two chemically distinct monomer reactants, and are commonly referred to interchangeably as “random” in the polymer literature.
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A dimer of the VS ribozyme from Neurospora. Monomer 1 in white, monomer 2 in grey. Magnesium ions in yellow, potassium ions in purple.() The Varkud satellite (VS) ribozyme is an RNA enzyme that carries out the cleavage of a phosphodiester bond.
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Many or even most synthetic polymers are in fact copolymers, containing about 1-20% of a minority monomer. In such cases, blockiness is undesirable. A block index has been proposed as a quantitative measure of blockiness or deviation from random monomer composition.
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Line and cartoon representation of an IFNγ monomer. The biologically active dimer is formed by anti-parallel inter-locking of the two monomers as shown below. In the cartoon model, one monomer is shown in red, the other in blue. Figure 2.
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Sequential monomer addition is the dominant method, also this simple approach suffers some limitations. Moreover, this strategy, enables synthesis of linear block copolymer structures that are not accessible via sequential monomer addition. For common A-b-B structures, sequential block copolymerization gives access to well defined block copolymers only if the crossover reaction rate constant is significantly higher than the rate constant of the homopolymerization of the second monomer, i.e., kAA >> kBB.
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Further polymerization is not possible, and the polymer is stable to subsequent molecular weight changes. Another method of achieving the desired molecular weight is by addition of a small amount of monofunctional monomer, a monomer with only one functional group. The monofunctional monomer, often referred to as a chain stopper, controls and limits the polymerization of bifunctional monomers because the growing polymer yields chain ends devoid of functional groups and therefore incapable of further reaction.
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Over time, the monomeric material dimerizes to give the parent azobenzene-N,N′-dioxide as a pale yellow solid. As dictated by Le Châtelier's principle, nitrosobenzene exists in the solution phase as a mixture of monomer and dimer in dynamic equilibrium whose composition is dependent on temperature (monomer favored at higher temperature) and concentration (monomer favored at low concentration), as well as the identity of the solvent. Structure of 2-nitrosotoluene dimer.
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Structure of a typical titanium alkoxide, e.g. titanium ethoxide (organic substituents removed for clarity). Like most titanium alkoxides (exception: titanium isopropoxide), Ti(OBu)4 is not a monomer but exists as a cluster (see titanium ethoxide). Nonetheless it is often depicted as a simple monomer.
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Modern Skydrol compatible seals are usually made from EPDM (ethylene propylene diene monomer) or PTFE (polytetrafluroethylene).
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BPDA or biphenyl-tetracarboxylic acid dianhydride is a monomer used in the production of some polyimides.
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The identity of the organic solvent is of utmost importance, as it affects several other factors such as monomer diffusion, reaction rate, and polymer solubility and permeability. The number of functional groups present on the monomer is also important, as it affects the polymer topology: a di-substituted monomer will form linear chains whereas a tri- or tetra-substituted monomer forms branched polymers. Most interfacial polymerizations are synthesized on a porous support in order to provide additional mechanical strength, allowing delicate nano films to be used in industrial applications. In this case, a good support would consist of pores ranging from 1 to 100 nm.
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This method has proven to be extremely popular; antistatic coatings are prepared on a commercial scale using ferric chloride. In addition to ferric chloride, other oxidizing agents. Slow addition of ferric chloride to the monomer solution produced poly(3-(4-octylphenyl)thiophene)s with approximately 94% H–T content. Precipitation of ferric chloride in situ (in order to maximize the surface area of the catalyst) produced significantly higher yields and monomer conversions than adding monomer directly to crystalline catalyst.
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Suspension polymerization is divided into two main types, depending on the morphology of the particles that result. In bead polymerization, the polymer is soluble in its monomer and the result is a smooth, translucent bead. In powder polymerization, the polymer is not soluble in its monomer and the resultant bead will be porous and irregular. The morphology of the polymer can be changed by adding a monomer diluent, an inert liquid that is insoluble with the liquid matrix.
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Based on definition from IUPAC, coordination polymerization is a chain polymerization that involves the preliminary coordination of a monomer molecule with a chain carrier. The monomer is firstly coordinated with the transition metal active center, and then the activated monomer is inserted into the transition metal-carbon bond for chain growth. In some cases, coordination polymerization is also called insertion polymerization or complexing polymerization. Advanced coordination polymerizations can control the tacticity, molecular weight and PDI of the polymer effectively.
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In this scenario, intermolecular forces between the solvent and monomer subunits dominate over intramolecular interactions. In a bad solvent or poor solvent, intramolecular forces dominate and the chain contracts. In the theta solvent, or the state of the polymer solution where the value of the second virial coefficient becomes 0, the intermolecular polymer-solvent repulsion balances exactly the intramolecular monomer-monomer attraction. Under the theta condition (also called the Flory condition), the polymer behaves like an ideal random coil.
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DETOSU- Bildungsreaktion DETOSU, in turn, is of important as a reactive monomer for the formation of polyorthoesters.
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The heat of formation of the trimer from the monomer (BFO)3 → 3BFO is 131 kcal/mol.
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An excimer can thus be measured by fluorescent emissions. Because excimer formation is dependent on a bimolecular interaction, it is promoted by high monomer density. Low-density conditions produce excited monomers that decay to the ground state before they interact with an unexcited monomer to form an excimer.
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The co-expression of homotetrameric wild type and mutant PKM2 in the cellular milieu resulting in the interaction between the two at the monomer level was substantiated further by in vitro experiments. The cross-monomer interaction significantly altered the oligomeric state of PKM2 by favoring dimerisation and heterotetramerization.
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In a slightly modified molecule, a polar group is added without changing the structure of the silicone hydrogel. This is referred to as the Tanaka monomer because it was invented and patented by Kyoichi Tanaka of Menicon Co. of Japan in 1979. Second-generation silicone hydrogels, such as galyfilcon A (Acuvue Advance, Vistakon) and senofilcon A (Acuvue Oasys, Vistakon), use the Tanaka monomer. Vistakon improved the Tanaka monomer even further and added other molecules, which serve as an internal wetting agent.
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When freshly prepared, it reverts rapidly to the monomer in solution. :Conversion of dihydroxyacetone dimer to monomer The monomer is very soluble in water, ethanol, diethyl ether, acetone and toluene. DHA may be prepared, along with glyceraldehyde, by the mild oxidation of glycerol, for example with hydrogen peroxide and a ferrous salt as catalyst. It can also be prepared in high yield and selectivity at room temperature from glycerol using cationic palladium-based catalysts with oxygen, air or benzoquinone acting as co-oxidants.
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As with other living radical polymerization techniques, RAFT allows chain extension of a polymer of one monomer with a second type of polymer to yield a block copolymer. In such a polymerisation, there is the additional challenge that the RAFT agent for the first monomer must also be suitable for the second monomer, making block copolymerisation of monomers of highly disparate character challenging. Multiblock copolymers have also been reported by using difunctional R groups or symmetrical trithiocarbonates with difunctional Z groups.
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As with most PFTs, lysenin oligomerization occurs in a two- step process, as was recently imaged. The process begins with monomers being adsorbed into the membrane by specific interactions, resulting in an increased concentration of monomers. This increase is promoted by the small area where the membrane receptor accumulates owing to the fact that the majority of PFT membrane receptors are associated with lipid rafts. Another side effect, aside from the increase of monomer concentration, is the monomer-monomer interaction.
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In equilibrium solution, negligibly small amounts of the monomer and at least one five- membered ring dimer exist.
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Electron spin resonance (ESR), nuclear magnetic resonance (NMR) and infrared spectroscopic (IR) measurements point to the presence of an equilibrium interconverting the monomeric and dimeric forms. ESR evidence confirms that the monomer possesses a high order axis of symmetry (Cn, n > 2) with a mirror plane (σ) perpendicular to it as symmetry elements; this experimentally demonstrates that the monomer does possess the typical sandwich structure of a metallocene although the interpretation of the ESR data has been questioned. The decomposition pathway of the monomer has also been studied by mass spectrometry. The dimerisation is a redox process; the dimer is a rhodium(I) species and the monomer has a rhodium(II) centre.
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Composition drift occurs during the process of free radical copolymerization causing variation in the instantaneous mole fraction of a monomer added to copolymer, therefore altering the chemical composition of the copolymer over the period of conversion. The degree of composition drift is directly affected by the reactivity ratios of each monomer in the copolymer system. Both the Mayo-Lewis equation and plot of the equation make evident that as monomer conversion increases, the copolymer composition will drift as the preferences for monomers change due to the interaction between reactivity ratios and the instantaneous concentration of each monomer. Composition drift in some degree will occur unless the reactivity ratios for both monomers are equal to 1.
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This is a special category of chain-growth supramolecular polymerization, where the monomer nucleates only in an early stage of polymerization to generate “seeds” and becomes active for polymer chain elongation upon further addition of a new batch of monomer. A secondary nucleation is suppressed in most of the case and thus possible to realize a narrow polydispersity of the resulting supramolecular polymer. In 2007, Ian Manners and Mitchell A. Winnik introduced this concept using a polyferrocenyldimethylsilane–polyisoprene diblock copolymer as the monomer, which assembles into cylindrical micelles. When a fresh feed of the monomer is added to the micellar “seeds” obtained by sonication, the polymerization starts in a living polymerization manner.
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The selectivity is also determined by the covalent and non-covalent interactions between the target molecule and monomer functional groups. The careful choice of functional monomer is another important choice to provide complementary interactions with the template and substrates."Characteristic and Synthetic Approach of Molecularly Imprinted Polymer" Int. J. Mol. Sci.
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Polyethylene is a polymer consisting of long chains of the monomer ethylene (IUPAC name ethene). The recommended scientific name polyethene is systematically derived from the scientific name of the monomer.[1] [2] In certain circumstances it is useful to use a structure–based nomenclature. In such cases IUPAC recommends poly(methylene).
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Acrylic can be a chemical irritant or allergen, resulting in Acrylic monomer dermatitis from the decomposition of methyl methacrylate.
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Allyl glycidyl ether is used in adhesives and sealants and as a monomer for various types of polymer preparations.
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Polyvinylpyrrolidone (PVP), also commonly called polyvidone or povidone, is a water-soluble polymer made from the monomer N-vinylpyrrolidone.
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ASL is composed of four identical monomers; each monomer consisting of a single polypeptide chain between 49 and 52 kDa, between 196 and 208 kDa for the entire tetrameric enzyme. Each monomer has three highly conserved regions remote from one another, but these regions cluster together in the tetramer to form four active sites. Therefore, each ASL homotetramer has four active sites to catalyze the breakdown of argininosuccinate. Each monomer in the ASL homotetramer is composed of three structural domains; all three are primarily alpha helical.
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Most photopolymerization reactions are chain-growth polymerizations which are initiated by the absorption of visible or ultraviolet light. The light may be absorbed either directly by the reactant monomer (direct photopolymerization), or else by a photosensitizer which absorbs the light and then transfers energy to the monomer. In general only the initiation step differs from that of the ordinary thermal polymerization of the same monomer; subsequent propagation, termination and chain transfer steps are unchanged.Allcock H.R., Lampe F.W. and Mark J.F. Contemporary Polymer Chemistry (3rd ed.
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The hexamer-monomer conversion is one of the central aspects of insulin formulations for injection. The hexamer is far more stable than the monomer, which is desirable for practical reasons; however, the monomer is a much faster-reacting drug because diffusion rate is inversely related to particle size. A fast-reacting drug means insulin injections do not have to precede mealtimes by hours, which in turn gives people with diabetes more flexibility in their daily schedules. Insulin can aggregate and form fibrillar interdigitated beta-sheets.
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The C-terminal region of alpha-glucuronidase is mainly alpha-helical. It wraps around the catalytic domain, making additional interactions both with the N-terminal domain of its parent monomer and also forming the majority of the dimer-surface with the equivalent C-terminal domain of the other monomer of the dimer.
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The monomer in step-growth polymerization will be consumed very quickly to dimer, trimer or oligomer. The degree of polymerization will increase steady during the whole polymerization process. On the other hand, in chain-growth polymerization, the monomer consumed steadily but the degree of polymerization could be increased very quickly after chain initiation.
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In 2009, Der f 1 was the first observed instance of a natural allergen in the form of a monomer.
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Chain growth polycondensation polymerizations were initially developed under the premise that a change in substituent effects of the polymer, relative to the monomer, causes the polymers end group to be more reactive this has been referred to as "reactive intermediate polycondensation". The essential result is monomers preferentially react with the activated polymer end groups over reactions with other monomers. This preferred reactivity is the fundamental difference when categorizing a polymerization mechanism as chain-growth as opposed to step-growth in which the monomer and polymer chain end group have equal reactivity (the reactivity is uncontrolled). Several strategies were employed to minimize monomer-monomer reactions (or self-condensation) and polymerizations with low D and controllable Mn have been attained by this mechanism for small molecular weight polymers.
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Each monomer has an active site, which however requires the N-terminal of another monomer to be completed (salt bridges to phosphate and entrance way). The phosphopyridoxyl group is attached to a lysine residue located in the central section of these enzymes and is stabilised by π-stacking interactions with a tyrosine residue above it.
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Fig 4. An example of utilization of amine pendant as recognization site to direct site- specific addition of monomer In this approach, a recognition site at polymer is offered to non-covalently anchor the monomer at polymer chain, which can subsequently go through a chemical insertion into polymeric backbone. One successful example demonstrates that methacrylic acid (monomer) can be radically incorporated into a backbone featuring a recognizable cationic site (protonated primary amine pendant). Driven by this site-specific reaction, the sequence-controlled polymerization can be achieve by using a template adorned with differenrt recognizable pendants.
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Each monomer of creatinase has two clearly defined domains, a small N-terminal domain, and a large C-terminal domain. Each of the two active sites is made by residues of the large domain of one monomer and some residues of the small domain of the other monomer. It has been suggested that a sulfhydryl group is located on or near the active site of the enzyme following inhibition experiments. Creatinase has been found to be most active at pH 8 and is most stable between ph 6-8 for 24 hrs.
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After initial addition of monomer to the initiator system, the viscosity would increase (due to increased polymer chain growth), but eventually cease after depletion of monomer concentration. However, he found that addition of more monomer caused an increase in viscosity, indicating growth of the polymer chain, and thus concluded that the polymer chains had never been terminated. This was a major step in polymer chemistry, since control over when the polymer was quenched, or terminated, was generally not a controlled step. With this discovery, the list of potential applications expanded dramatically.
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The important thing to note about ring-opening metathesis polymerizations is that the double bond is usually maintained in the backbone, which can allow it to be considered "living" under the right conditions. For a ROMP reaction to be considered "living", several guidelines must be met: # Fast and complete initiation of the monomer. This means that the rate at which an initiating agent activates the monomer for polymerization, must happen very quickly. # How many monomers make up each polymer (the degree of polymerization) must be related linearly to the amount of monomer you started with.
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The catalytic cycle of a living ring-opening metathesis polymerization with a metal catalyst. Note that the ring can be any size, but should contain some significant ring strain on the alkene. Because living polymers have had their termination ability removed, this means that once your monomer has been consumed, the addition of more monomer will result in the polymer chains continuing to grow until all of the additional monomer is consumed. This will continue until the metal catalyst at the end of the chain is intentionally removed by the addition of a quenching agent.
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In recursive directional ligation, the gene encoding the monomer is inserted into a plasmid with restriction sites that are recognized by at least two endonucleases. The endonucleases will cut the plasmid, releasing the gene of interest. Then, this single gene is inserted into a recipient plasmid vector already containing one copy of the ELP monomer gene via digestion of the recipient plasmid with the same restriction endonucleases used on the donor plasmid and a subsequent ligation step. From this process, a sequence of two ELP monomer genes is retrieved.
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Due to his involvement in the synthesis of the isoprene monomer, Spence was the first recipient of the Charles Goodyear Medal.
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4-Methyl-1-pentene is used as a monomer for olefin polymerisation. The resulting polymer is poly(4-methyl-1-pentene).
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For the first method, fragile glass capillaries or fibers are imbedded within a composite material. (Note: this is already a commonly used practice for strengthening materials. See Fiber-reinforced plastic.) The resulting porous network is filled with monomer. When damage occurs in the material from regular use, the tubes also crack and the monomer is released into the cracks.
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Polychlorotrifluoroethylene (PCTFE or PTFCE) is a thermoplastic chlorofluoropolymer with the molecular formula (CF2CClF)n, where n is the number of monomer units in the polymer molecule. It is similar to polytetrafluoroethene (PTFE), except that it is a homopolymer of the monomer chlorotrifluoroethylene (CTFE) instead of tetrafluoroethene. It has the lowest water vapor transmission rate of any plastic.
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Based on the chemical structure of photoresists, they can be classified into three types: photopolymeric, photodecomposing, photocrosslinking photoresist. Photopolymeric photoresist is a type of photoresist, usually allyl monomer, which could generate free radical when exposed to light, then initiates the photopolymerization of monomer to produce a polymer. Photopolymeric photoresists are usually used for negative photoresist, e.g. methyl methacrylate.
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Another useful reaction is the use of zirconium metallocene complexes to copolymerize olefin with borane monomer. After reaction with a borane monomer, such as 9-borabicyclonoane (9-BBN), subsequent functionalization can result in hydroxyl functionalities. Turning from early transition metals to late transition metals, palladium and nickel catalysts have been used to copolymerize ethylene and methylacrylate.
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For thermosetting plastics that require only one monomer, the monomer compound is the "resin". For example, liquid methyl methacrylate is often called the "resin" or "casting resin" while in the liquid state, before it polymerizes and "sets". After setting, the resulting PMMA is often renamed acrylic glass, or "acrylic". (This is the same material called Plexiglas and Lucite).
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3D structures of MPO and PGHS have been reported. MPO is a homodimer: each monomer consists of a light (A or B) and a heavy (C or D) chain resulting from post-translational excision of 6 residues from the common precursor. Monomers are linked by a single inter- chain disulfide. Each monomer includes a bound calcium ion.
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Toluene, 1,4-dioxane, xylene, anisole, DMF, DMSO, water, methanol, acetonitrile, or even the monomer itself (described as a bulk polymerization) are commonly used.
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Mammalian FAS consists of a homodimer of two identical protein subunits, in which three catalytic domains in the N-terminal section (-ketoacyl synthase (KS), malonyl/acetyltransferase (MAT), and dehydrase (DH)), are separated by a core region of 600 residues from four C-terminal domains (enoyl reductase (ER), -ketoacyl reductase (KR), acyl carrier protein (ACP) and thioesterase (TE)). The conventional model for organization of FAS (see the 'head-to-tail' model on the right) is largely based on the observations that the bifunctional reagent 1,3-dibromopropanone (DBP) is able to crosslink the active site cysteine thiol of the KS domain in one FAS monomer with the phosphopantetheine prosthetic group of the ACP domain in the other monomer. Complementation analysis of FAS dimers carrying different mutations on each monomer has established that the KS and MAT domains can cooperate with the ACP of either monomer. and a reinvestigation of the DBP crosslinking experiments revealed that the KS active site Cys161 thiol could be crosslinked to the ACP 4'-phosphopantetheine thiol of either monomer.
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Stephacidin B rapidly converts into the electrophilic monomer avrainvillamide in cell culture, and there is evidence that the monomer avrainvillamide interacts with intracellular thiol- containing proteins, most likely by covalent modification. Conversion of dimer Stephacidin B to monomer Avrainvillamide Avrainvillamide, which contains a 3-alkylidene-3H-indole 1-oxide function, was identified in culture media from various strains of Aspergillus and is reported to exhibit antimicrobial activity against multidrug-resistant bacteria. The avrainvillamide and stephacidins family of structurally complex anticancer natural products are active against the human colon HCT 116 cell line. The signature bicyclo[2.2.
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This free radical then reacts with a molecule of the monomer to form the active center with additional molecules of monomer then adding in a sequential fashion to produce a growing polymer chain (Pn•). The propagating chain adds to the CTA (1) to yield a radical intermediate. Fragmentation of this intermediate gives rise to either the original polymer chain (Pn•) or to a new radical (R•), which itself must be able to reinitiate polymerization. This free radical generates its own active center by reaction with the monomer and eventually a new propagating chain (Pm•) is formed.
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In 2015, Aida realized the first example of chain-growth supramolecular polymerization, where a bowl-shaped, corannulene- based monomer, rendered non-polymerizable by an intramolecular hydrogen- bonding network, is forced to polymerize by the action of a corresponding initiator that can reorganize the intramolecular hydrogen-bonding network into an intermolecular one. The polymer molecular weight is uniform and tunable by changing the monomer-to-initiator mole ratio. Furthermore, sequential polymerization of two monomers with this system leads to well-defined block copolymers. The chain growth is also perfectly homochiral, even when a racemic chiral monomer is polymerized.
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Monomer structure of 2,3-dihydro-2,3-dihydroxybenzoate dehydrogenase. 2,3-diDHB dehydrogenase is a tetramer protein with dimension 65x69x43 Å. It has a crystallographic 222 symmetry, which exhibited for other members of short- chain oxireductase (SCOR) family of enzymes. The length of each monomer is 248 residues and the weight of the protein is 24647 Da. Each monomer consists of 7 beta-pleated sheets and 6 alpha helices. Although the structure of the binding protein is not clearly defined, it was proposed that the binding pocket is made out of Leu83, Met85, Arg138, Gly140, Met141, Ser176, Met181, Gln182 and Leu185.
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One of the simplest repeat units is that of the addition polymer polyvinyl chloride, -[CH2-CHCl]n-, whose repeat unit is -[CH2-CHCl]-. In this case the repeat unit has the same atoms as the monomer vinyl chloride CH2=CHCl. When the polymer is formed, the C=C double bond in the monomer is replaced by a C-C single bond in the polymer repeat unit, which links by two new bonds to adjoining repeat units. In condensation polymers (see examples below), the repeat unit contains fewer atoms than the monomer or monomers from which it is formed.
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DNA Pol II is an 89.9 kD protein, composed of 783 amino acids, that is encoded by the polB (dinA) gene. A globular protein, DNA Pol II functions as a monomer, whereas many other polymerases will form complexes. There are three main sections of this monomer colloquially referred to as the palm, fingers, and thumb. This “hand” closes around a strand of DNA.
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Another monomer whose homo- and co-polymers exhibit LCST behavior in solution is 2-(dimethylamino)ethyl methacrylate. The LCST depends on the polymer preparation and in the case of copolymers, the monomer ratios, as well as the hydrophobic or hydrophilic nature of the polymer. To date, over 70 examples of non-ionic polymers with an LCST in aqueous solution have been found.
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Twinfilin-1 is a protein that in humans is encoded by the TWF1 gene. This gene encodes twinfilin, an actin monomer-binding protein conserved from yeast to mammals. Studies of the mouse counterpart suggest that this protein may be an actin monomer-binding protein, and its localization to cortical G-actin-rich structures may be regulated by the small GTPase RAC1.
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Human β-glucuronidase is synthesized as an 80 kDa monomer (653 amino acids) before proteolysis removes 18 amino acids from the C-terminal end to form a 78 kDa monomer. Beta- glucuronidase exists as a 332 kDa homotetramer. Beta-glucuronidase contains several notable structural formations, including a type of beta barrel known as a jelly roll barrel and a TIM barrel.
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As in the case of the Carmesin-Kremer BFM, the Shaffer BFM is also constructed on a simple-cubic lattice. However, the lattice points, or vertices of each cube are the sites that can be occupied by a monomer. Each lattice point can be occupied by one monomer only. Successive monomers along a polymer backbone are connected by bond vectors.
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Cracking produces a mixture of products, and the butene is extracted from this by fractional distillation. Butene can be used as the monomer for polybutene, but this polymer is more expensive than alternatives with shorter carbon chains such as polypropylene. Polybutene is therefore used in more specialized applications. Butenes are more commonly used to make copolymer (mixed with another monomer such as ethylene).
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Two major manufacturing routes exist for PEN, i.e. an ester or an acid process, named according to whether the starting monomer is a diester or a diacid derivative, respectively. In both cases for PEN, the glycol monomer is ethylene glycol. Solid-state polymerization (SSP) of the melt-produced resin pellets is the preferred process to increase the average molecular weight of PEN.
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When NBD and Rhodamine are within a certain distance, the Förster resonance energy transfer (FRET) happens. After fusion, resonance energy transfer (FRET) decreases when the average distance between probes increases, while NBD fluorescence increases. #Pyrene Excimer Formation: Pyrene monomer and excimer emission wavelengths are different. The emission wavelength of monomer is around 400 nm and that of excimer is around 470 nm.
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PEDOT is prepared by mixing EDT monomer with an oxidizing agent such as FeCl3. The oxidizing agent acts as an initiator for polymerization. Research has shown that increasing the ratio of [FeCl3]/[monomer] decreases the solubility of the PEDOT. This is thought to be a result of increased crosslinking in the polymer making it more difficult to dissolve in a solvent.
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The active form of mercury(II) reductase is found as a homodimer. It has a quaternary conformation and the monomer is composed of two domains.
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Leuco-fisetinidin, a flavan-3,4-diol (leucoanthocyanidin) and a monomer of the condensed tannins called profisetinidins, can be extracted from the heartwood of A. mearnsii.
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Pentaerythritol tetraacrylate (PETA or sometimes PETRA) is an organic compound. It is a tetrafunctional acrylate ester used as a monomer in the manufacture of polymers.
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Pyrolysis usually goes up to 430 °C. The high energy cost of doing this has made commercial recycling of polystyrene back into styrene monomer difficult.
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Leuco- fisetinidin, a flavan-3,4-diol (leucoanthocyanidin) and a monomer of the condensed tannins called profisetinidins, can be extracted from the heartwoods of S. balansae.
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GT198 is a small protein with its monomer contains 217 amino acids. It comprises a DNA- binding domain and forms a protein homodimer or heterodimer.
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Recent data support that rhodopsin is a functional monomer, instead of a dimer, which was the paradigm of G-protein-coupled receptors for many years.
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Meaning although they will start to melt quicker, they will take longer to fully change phases. # Polymers with large captodative stabilizations starting materials can quickly “unzip” to their starting monomer upon heating. # Bifunctional polymers, with two different functional groups at every monomer unit, are commonly formed from the captodative monomers. ## Dative groups substantially alter the solubility through Hydrogen bonding in specific bifunctional polymers( see figure above).
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They often form dimers, unlike their boron analogues, but this tendency diminishes for branched-chain alkyls (e.g. Pri, Bui, Me3CCH2); for example, triisobutylaluminium exists as an equilibrium mixture of the monomer and dimer.Greenwood and Earnshaw, pp. 257–67Martin B. Smith, Journal of Organometallic Chemistry, The Monomer-Dimer Equilibria of Liquid Ammonium Alkyls II Triisobutylaluminum Journal of Organometallic Chemistry, Volume 22, Issue 2, April 1970, Pages 273-281.
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The tRNA(Tyr) molecule has an L-shaped structure. Its recognition involves both subunits of the tyrosyl-tRNA synthetase dimer. The acceptor arm of tRNA(Tyr) interacts with the catalytic domain of one YARS monomer whereas the anticodon arm interacts with the C-terminal moiety of the other monomer. In most YARS structures, the monomers are related to each other by a twofold rotational symmetry.
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Solution-based polymerization is commonly used today for SAP manufacture of co-polymers, particularly those with the toxic acrylamide monomer. This process is efficient and generally has a lower capital cost base. The solution process uses a water-based monomer solution to produce a mass of reactant polymerized gel. The polymerization's own exothermic reaction energy is used to drive much of the process, helping reduce manufacturing cost.
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Homopolymerization :The process of free radical polymerization of a single type of monomer, in this case, N-isopropylacrylamide, to form the polymer is known as a homopolymerization. The radical initiator azobisisobutyronitrile (AIBN) is commonly used in radical polymerizations. :Homopolymerization of PNIPA Copolymerization :A free-radical polymerization of two different monomer results in a copolymerization. An advantage to a copolymerization includes fine tuning of the LCST.
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Ring opening polymerization is used to polymerize the monomer to nylon-12. The reaction can be brought about with cationic or anionic initiators or with water. Cationic polymerization with acid is believed to involve the initial O-protonation. Nucleophilic attack by the monomer on the reactive protonated nitrogen, followed by successive ring-opening acylation of the primary amine results in the formation of the polyamide.
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Living polymerization was first introduced by Michael Szwarc in 1956. Based on definition from IUPAC, it is a chain polymerization from which chain transfer and chain termination are absent. As there is no chain-transfer and chain termination, the monomer in the system is consumed and the polymerization is stopped when the polymer chain remains active. Once the new monomer is added, the polymerization can proceed.
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Synthesis of block copolymers is one of the most important applications of living polymerization as it offers the best control over structure. The nucleophilicity of the resulting carbanion will govern the order of monomer addition, as the monomer forming the less nucleophilic propagating species may inhibit the addition of the more nucleophilic monomer onto the chain. An extension of the above concept is the formation of triblock copolymers where each step of such a sequence aims to prepare a block segment with predictable, known molecular weight and narrow molecular weight distribution without chain termination or transfer.Hsieh, H.;Quirk, R. Anionic Polymerization: Principles and practical applications; Marcel Dekker, Inc: New York, 1996.
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Two monomers(left and right) are shown and the coenzyme PLP is placed in the crevice between the two domains. Two Dimers: Two monomers of hSDS (human SDH) come together to make a dimer. The interface between the two monomers is formed through hydrogen bonds and hydrophobic interactions. The monomer–monomer contacts involve six pairs of hydrogen bonds formed between 10 residues (Arg98-Asn260, Leu310-Asn260, and Leu265-Lys263). Additional interactions include a number of hydrophobic contacts between the residues Met17, Lys21, Asn101, Glu102, Ser306, Ile308, Ser309, and Ile264 in each monomer. (Figure 2). File:PLPmoleculeSDH.jpg Figure 2 shows the PLP coenzyme situated in the active site of SDH.
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OPG is largely expressed by osteoblast lineage cells of bone, epithelial cells of the gastrointestinal tract, lung, breast and skin, vascular endothelial cells, as well as B-cells and dendritic cells in the immune system. OPG is a soluble glycoprotein which can be found as either a 60-kDa monomer or a 120-kDa dimer linked by disulfide bonds. The dimerisation of OPG is necessary for RANK-RANKL inhibition as dimerisation increases the affinity of OPG for RANKL (from a KD of 3µM as a monomer to 10nM as a dimer). As a monomer, OPG would have insufficient affinity for RANKL to compete with RANK and effectively suppress RANK-RANKL interactions.
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For carbohydrates, the monomers are monosaccharides. The most abundant natural monomer is glucose, which is linked by glycosidic bonds into the polymers cellulose, starch, and glycogen.
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The protein domain, YecM, is a monomer. The eight, mostly antiparallel beta-strands form around C-terminal alpha-helix. There are four alpha helices in total.
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Lacritin monomer, active form of lacritin, is selectively decreased in aqueous deficient dry eye, Sjögren syndrome dry eye, contact lens-related dry eye and in blepharitis.
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Organolithium-initiated polymerization of styrene Propagation in anionic addition polymerization results in the complete consumption of monomer. This stage is often fast, even at low temperatures.
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It may be used to produce herbicides and pesticides, intermediates for active pharmaceutical ingredients and can be used as a monomer for the production of polyimides.
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Many plasticizers are based on butyl esters, e.g., dibutyl phthalate. The monomer butyl acrylate is used to produce polymers. It is the precursor to n-butylamines.
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Note: This early report mistakes the trimer for the monomer. TCI America (2020): "Product H1278: 2,2,4,4,6,6-Hexamethyl-1,3,5-trithiane". Online catalog page, accessed on 2020-01-01.
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He was awarded the title of Distinguished Professor in 2010. Darensbourg's research interest includes using carbon dioxide as monomer and solvent in the production of biodegradable copolymers.
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Each regulatory monomer is in contact with one other regulatory chain and two catalytic chains. In the unliganded enzyme, the two catalytic trimers are also in contact.
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Frank Würthner achieved similar seeded supramolecular polymerization of amide functionalized perylene bisimide as monomer. Importantly, the seeded supramolecular polymerization is also applicable to prepare supramolecular block copolymers.
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The mechanism of ITP involves thermal decomposition of the radical initiator (typically persulfate), generating the initiating radical In•. This radical adds to the monomer M to form the species P1•, which can propagate to Pm•. By exchange of iodine from the transfer agent R-I to the propagating radical Pm• a new radical R• is formed and Pm• becomes dormant. This species can propagate with monomer M to Pn•.
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The mechanism of ITP involves thermal decomposition of the radical initiator (AIBN), generating the initiating radical In•. This radical adds to the monomer M to form the species P1•, which can propagate to Pm•. By exchange of iodine from the transfer agent R-I to the propagating radical Pm• a new radical R• is formed and Pm• becomes dormant. This species can propagate with monomer M to Pn•.
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Another DNA binding domain, the Helix-loop-helix (HLH) dimer, is shown bound to DNA fragment — each alpha helix represents a monomer. Leucine zipper is created by the dimerization of two specific alpha helix monomers bound to DNA. The leucine zipper is formed by amphipathic interaction between two ZIP domains. The ZIP domain is found in the alpha-helix of each monomer, and contains leucines, or leucine-like amino acids.
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Initiation of styrene polymerization with sodium naphthalene proceeds by electron transfer from the naphthalene radical anion to the monomer. The resulting radical dimerizes to give a dilithio compound, which then functions as the initiator. Polar solvents are necessary for this type of initiation both for stability of the anion-radical and to solvate the cation species formed. The anion-radical can then transfer an electron to the monomer.
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DAO exists as a dimer, with each monomer containing both an FBD and SBD. Each monomer is composed of 347 amino acids in human DAO, though among other eukaryotes the protein can range from 345 to 368 amino acids long. In human DAO, the two monomers are connected in a head-to-head fashion. DAO of other organisms, such as yeast, can be present as head-to-tail dimers.
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4-hydroxybenzoate 3-monooxygenase is a homodimer with a flavin bound to each monomer. The active site is composed of the flavin and amino acids on the monomer. The structure of this enzyme often serves as a model for structure-reactivity interdependence of other flavin- dependent hydroxylases. The active site limits potential substrates to substituted benzenes, namely 4-hydroxybenzoate (the native substrate), 2,4-dihydroxybenzoate, 4-mercaptobenzoate, and several halogenated aromatic compounds.
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New monomer adds to the initiator and to the active growing chain in a Michael reaction. With each addition of a monomer group the trimethylsilyl group is transferred to the end of the chain. The active chain-end is not ionic as in anionic or cationic polymeriation but is covalent. The reaction can be catalysed by bifluorides and bioxyanions such as tris(dialkylamino)sulfonium bifluoride or tetrabutyl ammonium bibenzoate.
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Orthovanadate V is used in protein crystallography to study the biochemistry of phosphate. The tetrathiovanadate [VS4]3− is analogous to the orthovanadate ion. At lower pH values, the monomer [HVO4]2− and dimer [V2O7]4− are formed, with the monomer predominant at vanadium concentration of less than c. 10−2M (pV > 2, where pV is equal to the minus value of the logarithm of the total vanadium concentration/M).
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A slight excess of one enantiomer of the chiral monomer resulted in a strong bias to either the right-handed or left-handed helical geometry at the supramolecular polymer level. In this case, a characteristic nonlinear dependence of the anisotropic factor, g, on the enantiomeric excess of a chiral monomer can be generally observed. Like in small molecule based chiral system, chirality of a supramolecular polymer also affected by chiral solvents.
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The oligomer is a combination of five monomers. The monomers are associated with another protein apimisin. The monomer is 55 kDa in mass, while apimisin is 5 kDa.
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The reaction of PPD with phosgene gives the diisocyanate, a precursor to urethane polymers. Molecular structure of Kevlar: the monomer subunit is bolded, dashed lines indicate hydrogen bonds.
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3-Chlorophthalic anhydride may be used to produce herbicides and pesticides, intermediates for active pharmaceutical ingredients and can be used as a monomer for the production of polyimides.
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In the gas phase above 320 °C the Raman spectrum is consistent with a pyramidal monomer containing a niobium–oxygen double bond. Gaseous NbOCl3 is a tetrahedral molecule.
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There are several assumptions made by these and similar models, including but not limited to uniformity of monomer concentration, temperature, and film density, and second-order reaction kinetics.
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Neopullulanase is a dimer of identical monomer subunits, each with four domains (N,A,B,C) that are highly conserved with other starch hydrolases, namely alpha-amylase, pullulanase, cyclomaltodextrin glucanotransferase, and 1,4-alpha-D-glucan branching enzyme (also known as glycogen branching enzyme). Like these enzymes, each monomer contains an active site at the carboxyl-terminus within a TIM barrel (also known as an alpha/beta barrel), an alpha/beta protein fold structure consisting of eight parallel beta-strands connected by eight external alpha-helices. This conserved structural domain is estimated to occur in roughly 10% of all proteins and may evolutionarily link neopullulanase and the similar starch hydrolases to a much larger family of enzymes, though the domain's common ancestry is debated due to a lack of conclusive sequence homology. In neopullulanase the barrel is located within domain A with its active site straddling domain A of one monomer with domain N of the other monomer.
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Copolymerization is particularly useful in tuning the glass transition temperature, which is important in the operating conditions of polymers; it is assumed that each monomer occupies the same amount of free volume whether it is in a copolymer or homopolymer, so the glass transition temperature (Tg) falls between the values for each homopolymer and is dictated by the mole or mass fraction of each component. A number of parameters are relevant in the composition of the polymer product; namely, one must consider the reactivity ratio of each component. Reactivity ratios describe whether the monomer reacts preferentially with a segment of the same type or of the other type. For example, a reactivity ratio that is less than one for component 1 indicates that this component reacts with the other type of monomer more readily. Given this information, which is available for a multitude of monomer combinations in the “Wiley Database of Polymer Properties”,Greenley, Robert.
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The chemical name acetone peroxide is most commonly used to refer to the cyclic trimer, the product of a reaction between two precursors, hydrogen peroxide and acetone, in an acid-catalyzed nucleophilic addition, although various further monomeric and dimeric forms are possible. Synthesis of tri-cyclic acetone peroxide. Specifically, two dimers, one cyclic (C6H12O4) and one open chain (C6H14O4), as well as an open chain monomer (C3H8O4),This is not the DMDO monomer referred to in the Chembox, but rather the open chain, dihydro monomer described by Milas & Goluboviç, op. cit. can also be formed; under a particular set of conditions of reagent and acid catalyst concentration, the cyclic trimer is the primary product.
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The current dominant belief is that a "cap" of GTP is required at the ends of the ParM polymer strands to prevent them from hydrolyzing. Although GTP is hydrolyzed by the ParM units after attachment, it is believed that the energy that drives the plasmids is derived from the Gibbs free energy of the ParM monomer concentrations, and not the energy released from GTP hydrolysis. The concentrations of ParM monomer and polymer must be kept out of equilibrium at the ends where attachment is occurring for the reaction to proceed regardless of GTP concentrations. Once the ParM has pushed plasmids to opposite ends of the cell the polymer rapidly depolymerizes—returning the monomer units to the cytoplasm.
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An advantage of this system is that reactivity ratios can be found using tabulated Q-e values of monomers regardless or what the monomer pair is in the system.
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In the industrial setting, sebacic acid and its homologues such as azelaic acid can be used as a monomer for nylon 610, plasticizers, lubricants, hydraulic fluids, cosmetics, candles, etc.
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Depolymerization (or depolymerisation) is the process of converting a polymer into a monomer or a mixture of monomers.Depolymerization, IUPAC Goldbook This process is driven by an increase in entropy.
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N-Vinylacetamide (NVA) is a non-ionic monomer. Copolymers made of NVA and other monomers can exhibit practical characteristics in addition to those common with the existing hydrophilic polymers.
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Additionally, the monomer must flow at a sufficient rate (have low enough viscosity) to cover the entire crack before it is polymerized, or full healing capacity will not be reached. Finally, the catalyst must quickly dissolve into the monomer in order to react efficiently and prevent the crack from spreading further. Scheme 6. ROMP of DCPD via Grubbs' catalyst This process has been demonstrated with dicyclopentadiene (DCPD) and Grubbs' catalyst (benzylidene- bis(tricyclohexylphosphine)dichlororuthenium).
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Formation of nuclei is energetically disfavored, but dimers and/or trimers can be catalyzed/stabilized by a number of cellular proteins. In excess of a 2:1 actin:gelsolin stoichiometry and in the presence of Ca2+, gelsolin will bind three actin monomers. A monomer adds to the trimer creating a tetramer that undergoes an internal conversion to an active tetramer witnessed by a concentration-independent lag phase. Subsequent fibrilization proceeds by monomer addition.
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Calculation of reactivity ratios generally involves carrying out several polymerizations at varying monomer ratios. The copolymer composition can be analysed with methods such as Proton nuclear magnetic resonance, Carbon-13 nuclear magnetic resonance, or Fourier transform infrared spectroscopy. The polymerizations are also carried out at low conversions, so monomer concentrations can be assumed to be constant. With all the other parameters in the copolymer equation known, r_1\, and r_2\, can be found.
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Negative regulation of L-arabinose operon via AraC protein When arabinose is absent, cells do not need the araBAD products for breaking down arabinose. Therefore, dimeric AraC acts as a repressor: one monomer binds to the operator of the araBAD gene (araO2), another monomer binds to a distant DNA half site known as araI1. This leads to the formation of a DNA loop. This orientation blocks RNA polymerase from binding to the araBAD promoter.
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An example of alkene polymerization, in which each styrene monomer's double bond reforms as a single bond plus a bond to another styrene monomer. The product is polystyrene. In polymer chemistry, polymerization (American English), or polymerisation (British English), is a process of reacting monomer molecules together in a chemical reaction to form polymer chains or three-dimensional networks.Young, R. J. (1987) Introduction to Polymers, Chapman & Hall International Union of Pure and Applied Chemistry, et al.
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A step-growth copolymer -(-A-A-B-B-)n\- formed by the condensation of two bifunctional monomers A–A and B–B is in principle a perfectly alternating copolymer of these two monomers, but is usually considered as a homopolymer of the dimeric repeat unit A-A-B-B. An example is nylon 66 with repeat unit -OC-( CH2)4-CO-NH-(CH2)6-NH-, formed from a dicarboxylic acid monomer and a diamine monomer.
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B1 elements in rats and mice are similar to Alus in that they also evolved from 7SL RNA, but they only have one left monomer arm. 95% percent of human Alus are also found in chimpanzees, and 50% of B elements in mice are also found in rats. These elements are mostly found in introns and upstream regulatory elements of genes. The ancestral form of Alu and B1 is the fossil Alu monomer (FAM).
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Vinyl chloride is a chemical intermediate, not a final product. Due to the hazardous nature of vinyl chloride to human health there are no end products that use vinyl chloride in its monomer form. Polyvinyl chloride (PVC) is very stable, storable, and nowhere near as acutely toxic as the vinyl chloride monomer (VCM). Vinyl chloride liquid is fed to polymerization reactors where it is converted from a monomeric VCM to a polymeric PVC.
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According to definition from IUPAC ring-opening polymerization is a polymerization in which a cyclic monomer yields a monomeric unit which is acyclic or contains fewer cycles than the monomer. Generally, the ring-opening polymerization is carried out under mild conditions, and the by-product is less than the polycondensation reaction and the high molecular weight polymer is easily obtained. Common ring-opening polymerization products includes polypropylene oxide, polytetrahydrofuran, polyepichlorohydrin, polyoxymethylene, polycaprolactam and polysiloxane.
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Polylactic acid can be chemically recycled to monomer by thermal depolymerization or hydrolysis. When purified, the monomer can be used for the manufacturing of virgin PLA with no loss of original properties (cradle-to-cradle recycling). End-of-life PLA can be chemically recycled to methyl lactate by transesterification. # Composting: PLA is biodegradable under industrial composting conditions, starting with chemical hydrolysis process, followed by the microbial digestion, to ultimately degrade the PLA.
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This gives a total of four FAD molecules and four acyl-CoA substrate binding sites per enzyme. FAD is bound between the three domains of the monomer, where only the nucleotide portion is accessible. FAD binding contributes significantly to overall enzyme stability. The acyl-CoA substrate is bound completely within each monomer of the enzyme. The active site is lined with the residues F252, T255, V259, T96, T99, A100, L103, Y375, Y375, and E376.
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This gland contains the several proteases involved in the cleavage of the precursor α-LTX molecule. The α-LTX protein tertiary structure can be divided in three parts: the N-terminal wing (36 kDa), the body (76 kDa), and the C-terminal head (18.5 kDa). Because of C-terminal ankyrin repeats, which mediate protein-protein interactions, the α-LTX monomer forms a dimer with another α-LTX monomer under normal conditions. Tetramer formation activates toxicity.
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The stability of the dimer is aided by several interactions at the interface between the DHps of each monomer. These include hydrophobic interactions between conserved hydrophobic residues as well as two hydrogen bonds (Thr-252...Glu-316’ and Arg-263...Asn-307’) and one salt bridge (Lys-270...Glu-303’). Further interactions are mediated via hydrogen bonds to water within a cavity inside the coiled coil and flanked by hydrophobic residues. Single monomer.
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Yashima and coworkers have used salt bridges to construct several polymers that adopt a double helix conformation much like DNA. In one example, they incorporated platinum to create a double helical metallopolymer. Starting from their monomer and platinum(II) biphenyl (Figure 8), their metallopolymer self assembles through a series of ligand exchange reactions. The two halves of the monomer are anchored together through the salt bridge between the deprotonated carboxylate and the protonated nitrogens.
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The name polyethylene comes from the ingredient and not the resulting chemical compound, which contains no double bonds. The scientific name polyethene is systematically derived from the scientific name of the monomer. The alkene monomer converts to a long, sometimes very long, alkane in the polymerization process. In certain circumstances it is useful to use a structure-based nomenclature; in such cases IUPAC recommends poly(methylene) (poly(methanediyl) is a non-preferred alternative).
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The natural membrane target of lysenin is an animal plasma membrane lipid called sphingomyelin located mainly in its outer leaflet, involving at least three of its phosphatidylcholines (PC) groups. Sphingomyelin is usually found associated with cholesterol in lipid rafts. Cholesterol, which enhances oligomerization, provides a stable platform with high lateral mobility where monomer-monomer encounters are more probable. PFTs have shown to be able to remodel the membrane structure, sometimes even mixing lipid phases.
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Each CLC channel is formed from two monomers, each monomer containing the antiparallel transmembrane domain. Each monomer has its own pore through which chloride and other anions may be conducted. Each channel or exchanger is composed of two similar subunits—a dimer—each subunit containing one pore. The proteins are formed from two copies of the same protein—a homodimer—though scientists have artificially combined subunits from different channels to form heterodimers.
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Each subunit binds ions independently of the other, meaning conduction or exchange occur independently in each subunit. A cartoon representation of a CLC channel monomer. Two of these subunits come together to form the CLC channel. Each monomer has three binding sites for anions, Sext, Scen, and Sint. The two CBS domains bind adenosine nucleotides to alter channel function Each subunit consists of two related halves oriented in opposite directions, forming an ‘antiparallel’ structure.
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Hydrolytic degradation of PLA generates the monomer lactic acid, which is metabolized via the tri-carboxylic acid cycle and eliminated as carbon dioxide. Hydrolytic Degradation of the aliphatic polyester, PLA.
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Martin B. Smith, Journal of Organometallic Chemistry, The Monomer-Dimer Equilibria of Liquid Ammonium Alkyls II Triisobutylaluminum Journal of Organometallic Chemistry, Volume 22, Issue 2, April 1970, Pages 273-281.
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An August 2015 review notes that dapsone is reported to be effective against generalized granuloma annulare. Dapsone has been use as a monomer in the design of dye adsorbent polymers.
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The apo crystal structure of EcoRII mutant R88A () has been solved at 2.1 Å resolution. The EcoRII monomer has two domains, N-terminal and C-terminal, linked through a hinge loop.
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Myosin XV is necessary for the development of the actin core structure of the non-motile stereocilia located in the inner ear. It is thought to be functional as a monomer.
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Studies have suggested that one metal ion bonds to each monomer of DAHP synthase. The reaction catalyzed by DAHP synthase is shown below. This is the reaction catalyzed by DAHP synthase.
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Of theoretical interest, molecular UF5 can be generated as a transient monomer by UV-photolysis of uranium hexafluoride. It is thought to adopt a square pyramidal geometry. Structure of molecular UF5.
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Figure 1. The FMO protein trimer. The BChl a molecules are depicted in green, the central magnesium atom in red and the protein in grey ("cartoons" representation). Each monomer contains bacteriochlorophylls.
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A GST monomer binds a glutathione molecule to its N-terminal glutathione-binding site. On the adjacent hydrophobic alpha-helical binding site on the C-terminal domain, the GST binds a hydrophobic xenobiotic molecule. Formation of the active site recruits another GST monomer to interact with the system and the enzymes dimerize. The active GST complex catalyzes the -SH residue on glutathione to perform a nucleophilic attack on electrophilic carbon, sulfur, or nitrogen atoms of the xenobiotic substrate.
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To modulate the reactivity between monomer and growing polymeric chain is another approach to enhance sequence control. The rationale for this method is that monomer has to be activated with first catalyst at beginning as a dormant species, which could then participate into polymerization as the second catalyst is introduced. A real example is utilization of HI as first catalyst and ZnI2 as second catalyst to achieve sequence-controlled polymerization of vinyl ethers and styrene derivatives.
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CR-39 is made by polymerization of diethyleneglycol bis allylcarbonate (ADC) in presence of diisopropyl peroxydicarbonate (IPP) initiator. The presence of the allyl groups allows the polymer to form cross-links; thus, it is a thermoset resin. The monomer structure is Monomer The polymerization schedule of ADC monomers using IPP is generally 20 hours long with a maximum temperature of 95 °C. The elevated temperatures can be supplied using a water bath or a forced air oven.
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Structure of AraC monomer The L-arabinose system is not only under the control of CAP-cAMP activator, but also positively or negatively regulated through binding of AraC protein. AraC functions as a homodimer, which can control transcription of araBAD through interaction with the operator and the initiator region on L-arabinose operon. Each AraC monomer is composed of two domains including a DNA binding domain and a dimerisation domain. The dimerisation domain is responsible for arabinose-binding.
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Vinyl neodecanoate is mainly used as a modifying monomer in conjunction with other monomers and particularly the manufacture of vinyl acetate based polymer emulsions by the process of emulsion polymerization. Vinyl neodecanoate-containing polymers are used in decorative emulsion paints, plasters and renders especially in Europe. Vinyl neodecanoate, like most vinyl ester monomers, is very hydrophobic and the structure is highly branched with a tertiary substituted α-carbon. It is used as a hydrophobic co-monomer.
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Another use of polyacrylamide is as a chemical intermediate in the production of N-methylol acrylamide and N-butoxyacrylamide. In oil and gas industry Polyacrylamide derivatives especially co-polymers of that have a substantial effect on unconventional production and hydraulic fracturing. As an nonionic monomer it can be co-polymerize with anionic for example Acrylic acid and cationic monomer such as diallyldimethyl ammonium chloride (DADMAC) and resulted co- polymer that can have different compatibility in different applications.
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These CD-actin dimers are reduced to CD-actin monomers as a result of ATP hydrolysis. The resulting CD-actin monomer can bind ATP-actin monomer to reform the CD-actin dimer. CD is very effective; only low concentrations (0.2 μM) are needed to prevent membrane ruffling and disrupt treadmilling. The effects of many different cytochalasins on actin filaments were analyzed and higher concentrations (2-20 μM) of CD were found to be needed to remove stress fibers.
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A monomer with functionality 3 has 3 functional groups which participate in the polymerization. This will introduce branching in a polymer and may ultimately form a cross-linked macrostructure. The point at which this three-dimensional 3D network is formed is known as the gel point, signaled by an abrupt change in viscosity. A more general functionality factor fav is defined for multi- chain polymerization, as the average number of functional groups present per monomer unit.
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Both the cyclooxygenase and the peroxidase active sites are located in the catalytic domain, which accounts for approximately 80% of the protein. The catalytic domain is homologous to mammalian peroxidases such as myeloperoxidase. It has been found that human PTGS2 (COX-2) functions as a conformational heterodimer having a catalytic monomer (E-cat) and an allosteric monomer (E-allo). Heme binds only to the peroxidase site of E-cat while substrates, as well as certain inhibitors (e.g.
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The fungal Ste50p SAM consists of six helices, which form a compact, globular fold. It is a monomer in solution and often undergoes heterodimerisation (and in some cases oligomerisation) of the protein.
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In contrast, the analogous trioxane compound, 2,2,4,4,6,6-hexamethyl-1,3,5-trioxane, with oxygen atoms in place of the sulfur atoms, seems to be unstable, while its corresponding monomer acetone (2-propanone) is stable.
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An average molar mass may be defined for mixtures of compounds. This is particularly important in polymer science, where different polymer molecules may contain different numbers of monomer units (non-uniform polymers).
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In the figure to the right, the crystal structure of the muscle-type M-CK monomer is shown. In vivo, two such monomers arrange symmetrically to form the active MM-CK enzyme.
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Polycarbonates do not have a unique resin identification code (RIC) and are identified as "Other", 7 on the RIC list. Products made from polycarbonate can contain the precursor monomer bisphenol A (BPA).
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The IIa sodium phosphate symporter isoform is a functional monomer, but it interacts with PDZ proteins which probably mediate apical sorting, parathyroid hormone-controlled endocytosis and/or lysosomal sorting of internalized transporters.
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While the elementary model described above is totally unadapted to the description of real-world polymers at the microscopic scale, it does show some relevance at the macroscopic scale in the case of a polymer in solution whose monomers form an ideal mix with the solvent (in which case, the interactions between monomer and monomer, solvent molecule and solvent molecule, and between monomer and solvent are identical, and the system's energy can be considered constant, validating the hypotheses of the model). The relevancy of the model is, however, limited, even at the macroscopic scale, by the fact that it does not consider any excluded volume for monomers (or, to speak in chemical terms, that it neglects steric effects). Other fluctuating polymer models that consider no interaction between monomers and no excluded volume, like the worm-like chain model, are all asymptotically convergent toward this model at the thermodynamic limit. For purpose of this analogy a Kuhn segment is introduced, corresponding to the equivalent monomer length to be considered in the analogous ideal chain.
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The carbonyl ligands in nickel tetracarbonyl are each bound through only a carbon atom and are hence described as monohapto ligands, but η1-notations are typically omitted in formulae. The cyclopentadienyl ligands in many metallocene and half-sandwich compounds are pentahapto ligands, hence the formula [Rh(η5-C5H5)2] for the rhodocene monomer. In the rhodocene dimer, the coupled cyclopentadienyl ligands are 4-electron tetrahapto donors to each rhodium(I) metal centre, in contrast to the 6-electron pentahapto cyclopentadienyl donors. The increased stability of the 18-valence electron rhodium(I) dimer species as compared to the 19-valence electron rhodium(II) monomer likely explains why the monomer is only detected under extreme conditions. protic solutions Cotton and Wilkinson demonstrated that the 18-valence electron rhodium(III) rhodocenium cation [Rh(η5-C5H5)2]+ can be reduced in aqueous solution to the monomeric form; they were unable to isolate the neutral product as not only can it dimerise, the rhodium(II) radical monomer can also spontaneously form the mixed-hapticity stable rhodium(I) species [(η5-C5H5)Rh(η4-C5H6)].
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Both mutations within the dimer interface and mutations distal to the interface can destabilize the association between the subunits. These experiments have shown in particular that the monomer of YARS is enzymatically inactive.
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Poly(4,4-dioctyl cyclopentadithiophene) is solution polymerized by combining monomer with iron(III) chloride. Once the polymerization is complete the doping is done by exposing the polymer to iodine vapor or DDQ solution.
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Electron-donating substituents lower the oxidation potential, whereas electron-withdrawing groups increase the oxidation potential. Thus, 3-methylthiophene polymerizes in acetonitrile and tetrabutylammonium tetrafluoroborate at a potential of about 1.5 V vs. SCE, whereas unsubstituted thiophene requires an additional 0.2 V. Steric hindrance resulting from branching at the α-carbon of a 3-substituted thiophene inhibits polymerization. In terms of mechanism, oxidation of the thiophene monomer produces a radical cation, which then couple with another monomer to produce a radical cation dimer.
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The Gag-Pol polyprotein, which contains premature coding proteins, including HIV-1 PR. PR is located between the reverse transcriptase (which is at the C-terminus of PR) and the p6pol (which is at the N-terminus of PR) of the transframe region (TFR). In order for this precursor to become a functional protein, each monomer must associate with another HIV-1 PR monomer to form a functional catalytic active site by each contributing the Asp25 of their respective catalytic triads.
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Thus, in the case of LiHMDS, TMEDA does not increase reactivity by reducing aggregation state. Also, as opposed to simple alkyllithium compounds, TMEDA does not deaggregate lithio-acetophenolate in THF solution. The addition of HMPA to lithium amides such as LiHMDS and LDA often results in a mixture of dimer/monomer aggregates in THF. However, the ratio of dimer/monomer species does not change with increased concentration of HMPA, thus, the observed increase in reactivity is not the result of deaggregation.
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ATM kinase, a member of the PI3-like family of serine/threonine kinases plays a critical role in maintaining the stability of the genome, which is of fundamental importance to the survival of all organisms. It exerts its effect by phosphorylating target proteins such as P53, MDM2 and chk2. Activation of ATM is facilitated by autophosphorylation. The inactive ATM exists as dimer, where the kinase domain of one monomer is bound to the internal domain of the other monomer, containing ser-1981.
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In an ideal system, these stabilized radical intermediates do not undergo termination reactions, but instead reintroduce a radical capable of reinitiation or propagation with monomer, while they themselves reform their C=S bond. The cycle of addition to the C=S bond, followed by fragmentation of a radical, continues until all monomer or initiator is consumed. Termination is limited in this system by the low concentration of active radicals and any termination that does occur is negligible. RAFT, invented by Rizzardo et al.
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Stable polymerizing cations are only possible using monomers with electron-releasing groups, and stable anions with monomers with electron-withdrawing groups as substituents. While radical polymerization rate is governed nearly exclusively by monomer chemistry and radical stability, successful ionic polymerization is as strongly related to reaction conditions. Poor monomer purity quickly leads to early termination, and solvent polarity has a great effect on reaction rate. Loosely-coordinated and solvated ion pairs promote more reactive, fast- polymerizing chains, unencumbered by their counterions.
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The carbonyl-component may be part of either a carboxylic acid group or the more reactive acyl halide derivative. The amine group and the carboxylic acid group can be on the same monomer, or the polymer can be constituted of two different bifunctional monomers, one with two amine groups, the other with two carboxylic acid or acid chloride groups. The condensation reaction is used to synthetically produce nylon polymers in industry. Nylons must specifically include a straight chain (aliphatic) monomer.
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The glycogen phosphorylase monomer is a large protein, composed of 842 amino acids with a mass of 97.434 kDa in muscle cells. While the enzyme can exist as an inactive monomer or tetramer, it is biologically active as a dimer of two identical subunits. R and T States of Glycogen Phosphorylase b Tower Helices, on the left and right respectively. Note the relative positioning of the central tower helices, as well as the increased interactions between subunits in the R state.
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Monomers for living cationic polymerization are electron- rich alkenes such as vinyl ethers, isobutylene, styrene, and N-vinylcarbazole. The initiators are binary systems consisting of an electrophile and a Lewis acid. The method was developed around 1980 with contributions from Higashimura, Sawamoto and Kennedy. Typically, generating a stable carbocation for a prolonged period of time is difficult, due to the possibility for the cation to be quenched by a β-protons attached to another monomer in the backbone, or in a free monomer.
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The E2 domain is the largest subdomain of APLP2 and consists of six alpha-helixes. The N-terminal double stranded coiled coil structure of the first monomer of E2 packs against the C-terminal triple stranded coiled coil structure of the second monomer. The BPTI/Kunitz inhibitor domain (residues 306-364) is ‘Cys-rich’ and is capable of inhibiting several proteases. The ectodomain of APLP2 is dimeric and contains multiple binding sites for metal ions and components of the extracellular matrix.
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This type of reaction can continue to build larger and larger silicon-containing molecules by the process of polymerization. Thus, a polymer is a huge molecule (or macromolecule) formed from hundreds or thousands of units called monomers. The number of bonds that a monomer can form is called its functionality. Polymerization of silicon alkoxide, for instance, can lead to complex branching of the polymer, because a fully hydrolyzed monomer Si(OH)4 is tetrafunctional (can branch or bond in 4 different directions).
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The distinct piece of each monomer that is incorporated into the polymer is known as a repeat unit or monomer residue. Synthetic methods are generally divided into two categories, step-growth polymerization and chain polymerization. The essential difference between the two is that in chain polymerization, monomers are added to the chain one at a time only,Sperling, p. 11 such as in polystyrene, whereas in step-growth polymerization chains of monomers may combine with one another directly,Sperling, p.
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Polystyrene is an addition polymer that results when styrene monomers interconnect (polymerization). In the polymerization, the carbon- carbon π bond of the vinyl group is broken and a new carbon-carbon σ bond is formed, attaching to the carbon of another styrene monomer to the chain. Since only one kind of monomer is used in its preparation, it is a homopolymer. The newly formed σ bond is stronger than the π bond that was broken, thus it is difficult to depolymerize polystyrene.
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EPM manufacture uses the same monomers as polyethene and polypropene, the ethylene and propylene monomers are randomly combined to yield a rubbery, stable polymer. By varying the monomer ratios and method by which the monomers are combined different forms of EPM can be formed (with a wide range of Mooney viscosities); ranging from amorphous to semi-crystalline. A third, non- conjugated diene monomer can be terpolymerized in a controlled manner to maintain a saturated backbone ready for vulcanization or polymer modification.
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Isoprene is a natural monomer that polymerizes to form natural rubber, most often cis-1,4-polyisoprene, but also trans-1,4-polymer. Synthetic rubbers are often based on butadiene, which is structurally related to isoprene.
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It is the precursor to polyvinylpyrrolidone (PVP), an important synthetic material. The NVP monomer is commonly used as a reactive diluent in ultraviolet and electron-beam curable polymers applied as inks, coatings or adhesives.
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Figure 2. Three conformations of FAN1 in action. A. Monomer scans substrate B. Dimerization occurs and dimer latches onto substrate C. dimer unwinds substrate. Created in PyMOL from PDB structures 4REA, 4REC, and 4REB.
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Polymerization of conjugated dienes such as buta-1,3-diene or isoprene (2-methylbuta-1,3-diene) results in largely 1,4-addition with possibly some 1,2-addition of the diene monomer to a growing polymer chain.
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There are five important variable components of atom transfer radical polymerizations. They are the monomer, initiator, catalyst, ligand, and solvent. The following section breaks down the contributions of each component to the overall polymerization.
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Butyl methacrylate is the organic compound with the formula C4H9O2CC(CH3)=CH2. A colorless liquid, it is a common monomer for the preparation of acrylate polymers.. It is typically polymerized under free-radical conditions.
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Ethyl methacrylate is the organic compound with the formula C2H5O2CC(CH3)=CH2. A colorless liquid, it is a common monomer for the preparation of acrylate polymers.. It is typically polymerized under free-radical conditions.
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Xylosan (1,4-anhydro-α-D-xylopyranose) is a molecule produced during pyrolysis of the hemicellulose found in wood. Xylosan is the dehydrated product of the 5-carbon xylose sugar monomer, a major component of hemicellulose.
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IUPAC defined chain propagation as an active center on the growing polymer molecule, which adds one monomer molecule to form a new polymer molecule which is one repeat unit longer with a new active center.
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Billions of kilograms of chlorodifluoromethane are produced annually as a precursor to tetrafluoroethylene, the monomer that is converted into Teflon.Rossberg, M. et al. (2006) "Chlorinated Hydrocarbons" in Ullmann's Encyclopedia of Industrial Chemistry, Wiley-VCH, Weinheim.
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DsbC is a modular dimer, with two 23.3 kDa subunits. There are four cysteines in each monomer, with two present in the active site. Modular dimer of DsbC. Each module shown in a different color.
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Together with guaiacol, syringol and its derivates are characteristic products of pyrolysis of lignin, being derived from the thermal decomposition of the sinapyl alcohol monomer. As such, syringol is an important component of wood smoke.
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Tetracycline-magnesium complex (blue) bound to cavity of TetR (green). HTH motif shown in pink -note conformational change. TetR functions as a homodimer. Each monomer consists of ten alpha helices connected by loops and turns.
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Prior to assembling the super-helix, each monomer is subjected to a number of post-translational modifications that occur while the monomer is being translated. First, on the order of 145 prolyl residues of the 239 in the triple-helical domain are hydroxylated to 4-hydroxyproline by prolyl-4-hydroxylase. Second, some of the lysine residues are hydroxylated or glycosylated, and some lysine as well as hydroxylysine residues undergo oxidative deamination catalysed by lysyl oxidase. Other post- translational modifications occur after the triple helix is formed.
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The polymers obtained from captodatively substituted starting materials exhibit "desirable" properties such as optical activity, differences in polarity, solvent affinity, thermal and mechanical stabilities. Substituents on the monomer can affect solvent affinities How a captodative monomer can form a polar polymer # Polymers with polar substituents are known to have interesting applications including within electrical and optical materials. # These polymers are typically transparent. # The Tdi (initial decomposition) of these polymers are relatively low compared to their analogues, but have relatively higher Tdm (maximum rate of weight change temperatures).
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However, it is now known that this monomer (residual monomer) is metabolized by the respiratory chain and split into carbon dioxide and water and excreted. Embolisms can always occur during anchorage of artificial joints when material is inserted into the previously cleared femoral canal. The result is intramedullary pressure increase, potentially driving fat into the circulation. If the patient is known to have any allergies to constituents of the bone cement, according to current knowledge bone cement should not be used to anchor the prosthesis.
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The type 2 copper center of a copper nitrite reductase is the active site of the enzyme. The Cu is bound by nitrogens of two Histidines from one monomer, and bound by one Histidine from another monomer; the Cys-His bridge to the type 1 Cu. This gives the molecule a distorted tetrahedral geometry. In the resting state, the Cu is also binding a water molecule that is displaced by nitrite. As nitrite displaces water, Cu is bound by both oxygens in a bidentate fashion.
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The structure of AQP4 consists of six-transmembrane domains and five connecting loops to form the channel. Through x-ray crystallography, it was found that “each AQP4 monomer consists of six helical, membrane-spanning domains and two short helical segments surrounding a narrow aqueous pore.” At the narrowest point the aqueous pore measures 2.8 angstroms, just large enough for the single-file passage of water molecules. While each monomer is individually capable of water transport, the quaternary structure of the channel is a tetramer.
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2-Acrylamido-2-methylpropane sulfonic acid (AMPS) was a Trademark name by The Lubrizol Corporation. It is a reactive, hydrophilic, sulfonic acid acrylic monomer used to alter the chemical properties of wide variety of anionic polymers. In the 1970s, the earliest patents using this monomer were filed for acrylic fiber manufacturing. Today, there are over several thousands patents and publications involving use of AMPS in many areas including water treatment, oil field, construction chemicals, hydrogels for medical applications, personal care products, emulsion coatings, adhesives, and rheology modifiers.
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The first is known as self-assembly, which involves the formation of polymer by combining all elements of the MIP and allowing the molecular interactions to form the cross-linked polymer with the template molecule bound. The second method of formation of MIPs involves covalently linking the imprint molecule to the monomer. After polymerization, the monomer is cleaved from the template molecule. The selectivity is greatly influenced by the kind and amount of cross-linking agent used in the synthesis of the imprinted polymer.
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Each of these biopolymers can be characterized as either a heteropolymer, meaning it consists of more than one monomer ordered in the backbone chain, or a homopolymer, which consists of just one repeating monomer. Polypeptides and nucleic acids are very commonly heteropolymers whereas common carbohydrate macromolecules such as glycogen can be homopolymers. This is because the chemical differences of peptide and nucleotide monomers determines the biological function of their polymers whereas common carbohydrate monomers have one general function such as for energy storage and delivery.
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There are also other interface categories, rarely used, including liquid-gas, solid-gas, and solid-solid. In a liquid- solid interface, polymerization begins at the interface, and results in a polymer attached to the surface of the solid phase. In a liquid-liquid interface with monomer dissolved in one phase, polymerization occurs on only one side of the interface, whereas in liquid-liquid interfaces with monomer dissolved in both phases, polymerization occurs on both sides. An interfacial polymerization reaction may proceed either stirred or unstirred.
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Gas discharge provided through this process initiates the polymerization of a group of monomers. Finally, pressure-induced polymerization applies pressure or compressive forces to solutions of monomers in order to create units which undergo polymerization and produce polymers. Another method tested in a study to produce sodium polyacrylate as an alternative to current methods began with Butyl acrylate-acrylic acid copolymer and poly (butyl acrylate). They were synthesized via suspension polymerization by using butyl acrylate as the main monomer and acrylic acid as a secondary monomer.
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SP Chemicals engages in the manufacture and sale of the chemical industry's basic building blocks - caustic soda, chlorine, hydrogen and its related downstream products. Their products are materials widely used in various applications across a diverse range of industries. Products include: aniline, caustic soda, chlorine, chlorobenzene, nitrochlorobenzene, nitrobenzene, vinyl chloride monomer (VCM). To further drive its growth, SP Chemicals plans to invest approximately RMB1.1 billion in facilities for the production of styrene monomer, an intermediate raw chemical used in making polystyrene plastics, protective coatings, polyesters and resins.
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Like most commercial alkene metathesis processes, this reaction does not employ a well-defined molecular catalyst. In addition to ROMP, norbornene monomers also undergo vinyl-addition polymerization, and is a popular monomer for use in Cyclic olefin copolymers. Polynorbornene is used mainly in the rubber industry for anti-vibration (rail, building, industry), anti-impact (personal protective equipment, shoe parts, bumpers) and grip improvement (toy tires, racing tires, transmission systems, transports systems for copiers, feeders, etc.) Ethylidene norbornene is a related monomer derived from cyclopentadiene and butadiene.
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A monomer unit is highlighted with the A chain in blue and the B chain in cyan. Yellow denotes disulfide bonds, and magenta spheres are zinc ions. Contrary to an initial belief that hormones would be generally small chemical molecules, as the first peptide hormone known of its structure, insulin was found to be quite large. A single protein (monomer) of human insulin is composed of 51 amino acids, and has a molecular mass of 5808 Da. The molecular formula of human insulin is C257H383N65O77S6.
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Two dimers then associate by way of alpha helix, one from each monomer, to form a central 20-helix core. The association of all four monomers allows for the catalytic activity at each possible active site.
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MRP is typically made from vulcanized elastomeric material, most often from end-of-life tire material, but can also be produced from post-industrial nitrile rubber, ethylene propylene diene monomer (EPDM), butyl and natural rubber compounds.
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Macromolecules are formed by many monomers linking together, forming a polymer. Carbohydrates are composed of carbon, oxygen, and hydrogen. The monomer of carbohydrates are monosaccharides. There are three forms of carbohydrates: energy, storage, and structural molecules.
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3,4-Epoxycyclohexanecarboxylate methyl ester is a cycloaliphatic epoxide, which is added as monovalent monomer to other monomers for the production of crosslinked epoxy resins. 3,4-Epoxycyclohexanecarboxylate methyl ester itself would give a linear polymer when homopolymerized.
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NADPH and Glu are shown as well. GLUD1 is a hexamer. The monomer unit has: # N-terminal Glu-BD(Binding domain) that is composed mostly of β-strands. # NAD-BD - can bind either NAD+ or NADP+.
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Ethylbenzene could be hydrogenated to form the flammable liquid monomer styrene. Styrene could be used to make the hydrocarbon polymer polystyrene. The Dow Physics Laboratory began working with styrene in 1931. Styrene was difficult to process.
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For a time it was used as a promoter chemical in the aluminium chloride catalyzed process to produce ethylbenzene, the precursor for styrene monomer. At present though, it is not widely used in any of these roles.
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The structures of the titanium alkoxides are often complex. Crystalline titanium methoxide is tetrameric with the molecular formula . Alkoxides derived from bulkier alcohols such as isopropylalcohol aggregate less. Titanium isopropoxide is mainly a monomer in nonpolar solvents.
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The results of the experiments have provided more suitable chemical structure of adhesive monomers, one is MDP.I. Omura, J. Yamauchi, “Correlation Between Molecular Structure of Adhesive Monomer and Adhesive Property”, International Congress on Dental Materials, 356 (1989).
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Trehalose is a disaccharide formed by a bond between two α-glucose units. Two other isomers are not found in nature. It is found in nature as a disaccharide and also as a monomer in some polymers.
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General reaction for forming a polyurea chain, illustrating the two monomer reactants and highlighting the urea linkage in the product The word polyurea is derived from the Greek words πολυ- - poly- meaning "many"; and ουρίας - oûron meaning "to urinate" (referring to the substance urea, found in urine). Urea or carbamide is an organic compound with the chemical formula (NH2)2CO. The molecule has two amine groups (–NH2) joined by a carbonyl functional group (C=O). In a polyurea, alternating monomer units of isocyanates and amines react with each other to form urea linkages.
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The structural characterization of phosphoglycolate phosphatase from Thermoplasma acidophilum (PDB 1L6R, pictured) revealed the monomer of the dimeric enzyme (indicated by the light blue and green coloring) includes two distinct domains, a smaller cap domain and a larger core domain. While the topology of the large domain is conserved, there is structural variation of the smaller domain. The active site of the protein is a continuous tunnel through the monomer and is lined with acidic residues, a feature consistent with other acid phosphatases. In addition, electrostatic surface analysis indicates a relatively acidic surface.
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IL-30 monomer is believed to have some functions similar to IL-27, even though there are more information and research on the IL-27 than IL-30. Both IL-27 and IL-30 alone can regulate inflammation by inhibiting Th17 cells production using STAT1 pathway. Although IL-30 has similar effect as IL-27 on the production of IL-17, it has a lower efficiency than IL-27. If secreted as a monomer, IL-30 was observed to act as a suppressor of the IL-27 signalling pathway.
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Ultra-high-molecular-weight polyethylene (UHMWPE) is synthesized from its monomer ethylene, which is bonded together to form the base polyethylene product. These molecules are several orders of magnitude longer than those of familiar high-density polyethylene (HDPE) due to a synthesis process based on metallocene catalysts, resulting in UHMWPE molecules typically having 100,000 to 250,000 monomer units per molecule each compared to HDPE's 700 to 1,800 monomers. UHMWPE is processed variously by compression moulding, ram extrusion, gel spinning, and sintering. Several European companies began compression molding UHMW in the early 1960s.
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Multiplying the ratio of monomer consumed to the concentration of the CTA used by the molecular weight of the monomer (mM) a reliable estimate of the number average molecular weight can be determined. RAFT is a degenerative chain transfer process and is free radical in nature. RAFT agents contain di- or tri-thiocarbonyl groups, and it is the reaction with an initiator, usually AIBN, that creates a propagating chain or polymer radical. This polymer chain then adds to the C=S and leads to the formation of a stabilized radical intermediate.
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Above 150 °C, dicyclopentadiene undergoes a retro-Diels–Alder reaction at an appreciable rate to yield cyclopentadiene. The reaction is reversible and at room temperature cyclopentadiene dimerizes over the course of hours to re-form dicyclopentadiene. Cyclopentadiene is a useful diene in Diels–Alder reactions as well as a precursor to metallocenes in organometallic chemistry. It is not available commercially as the monomer, due to the rapid formation of dicyclopentadiene; hence, it must be prepared by "cracking" the dicyclopentadiene (heating the dimer and isolating the monomer by distillation) shortly before it is needed.
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Each module uses one molecule of the selected substrate amino acid with one molecule of ATP to give an aminoacyl adenylate enzyme complex and pyrophosphate. The activated amino acid can then be transferred to the enzyme bound 4'-phosphopantetheine of the carrier protein with the expulsion of AMP from the system. The carrier protein uses the 4'-phosphopantetheine prosthetic group for loading of the growing peptide and their monomer precursors. Elongation of the peptide chain is achieved through condensation of the upstream PCP onto an adjacent downstream PCP-bound monomer.
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ABS is derived from acrylonitrile, butadiene, and styrene. Acrylonitrile is a synthetic monomer produced from propylene and ammonia; butadiene is a petroleum hydrocarbon obtained from the C4 fraction of steam cracking; styrene monomer is made by dehydrogenation of ethyl benzene — a hydrocarbon obtained in the reaction of ethylene and benzene. ABS combines the strength and for its hardness, gloss, toughness, and electrical insulation properties. According to the European plastic trade association PlasticsEurope, industrial production of of ABS resin in Europe uses an average of and is derived from natural gas and petroleum.
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Situated where the two lobes meet is an ATP binding site, which is covered by a tyrosine gatekeeper. Tyrosine as a gatekeeper is believed to be unique to the IRAK family of kinases. The protein also contains three auto-phosphorylation sites, each of which when mutated results in a decrease in the kinase activity of IRAK4. A structure of the autophosphorylation of the activation loop has been determined in which the activation loop Thr345 of one monomer is sitting in the active site of another monomer in the crystal (PDB: 4U9A, 4U97).
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Nylons are condensation polymers or copolymers, formed by reacting difunctional monomers containing equal parts of amine and carboxylic acid, so that amides are formed at both ends of each monomer in a process analogous to polypeptide biopolymers. Most nylons are made from the reaction of a dicarboxylic acid with a diamine (e.g. PA66) or a lactam or amino acid with itself (e.g. PA6). In the first case, the "repeating unit" consists of one of each monomer, so that they alternate in the chain, similar to the so-called ABAB structure of polyesters and polyurethanes.
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To properly control the polymer molecular weight, the stoichiometric imbalance of the bifunctional monomer or the monofunctional monomer must be precisely adjusted. If the nonstoichiometric imbalance is too large, the polymer molecular weight will be too low. It is important to understand the quantitative effect of the stoichiometric imbalance of reactants on the molecular weight. Also, this is necessary in order to know the quantitative effect of any reactive impurities that may be present in the reaction mixture either initially or that are formed by undesirable side reactions.
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In polymer science, dispersion polymerization is a heterogeneous polymerization process carried out in the presence of a polymeric stabilizer in the reaction medium. Dispersion polymerization is a type of precipitation polymerization, meaning the solvent selected as the reaction medium is a good solvent for the monomer and the initiator, but is a non-solvent for the polymer. As the polymerization reaction proceeds, particles of polymer form, creating a non-homogeneous solution. In dispersion polymerization these particles are the locus of polymerization, with monomer being added to the particle throughout the reaction.
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One universal distinction between polymerization types is development of molecular weight by the different modes of propagation. Addition polymers form high molecular weight chains rapidly, with much monomer remaining. Since addition polymerization has rapidly growing chains and free monomer as its reactants, and condensation polymerization occurs in step-wise fashion between monomers, dimers, and other smaller growing chains, the effect of a polymer molecule's current size on a continuing reaction is profoundly different in these two cases. This has important effects on the distribution of molecular weights, or polydispersity, in the finished polymer.
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CHS exists as a homodimeric protein with each monomer approximately 42-45 kDa in size. Each monomer possesses a β-keto synthase (KS) activity that catalyzes the sequential head to tail incorporation of two- carbon acetate units into a growing polyketide chain. CHS contains a five layer αβαβα core, a location of the active site and dimerization interface that is highly similar to thiolase-fold containing enzymes. The dimerization interface contains both hydrophobic and hydrophilic residues and is generally flat except for a pair of N-terminal helices that lay entwined across the top.
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Like all polymers, polysilazanes are built from one or several basic monomer units. Linking together of these basic units can result in polymeric chains, rings or three-dimensionally crosslinked macromolecules with a wide range of molecular mass. While the monomer unit describes the chemical composition and the connectivity of the atoms (coordination sphere) it does not illustrate the macro-molecular structure. idealized molecular structure of perhydropolysilazane In polysilazanes, each silicon atom is bound to two nitrogen atoms and each nitrogen atom to at least two silicon atoms (three bonds to silicon atoms are also possible).
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Conventional chain-growth polymerization involves at least two phases; initiation and propagation, while and in some cases termination and chain transfer phases also occur. Chain- growth supramolecular polymerization in a broad sense involves two distinct phases; a less favored nucleation and a favored propagation. In this mechanism, after the formation of a nucleus of a certain size, the association constant is increased, and further monomer addition becomes more favored, at which point the polymer growth is initiated. Long polymer chains will form only above a minimum concentration of monomer and below a certain temperature.
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They named this method as crystallization-driven self-assembly (CDSA) and is applicable to construct micron-scale supramolecular anisotropic structures in 1D–3D. A conceptually different seeded supramolecular polymerization is showed by Kazunori Sugiyasu in a porphyrin-based monomer bearing amide-appended long alkyl chains. At low temperature, this monomer preferentially forms spherical J-aggregates while fibrous H-aggregates at higher temperature. By adding a sonicated mixture of the J-aggregates (“seeds”) into a concentrated solution of the J-aggregate particles, long fibers can be prepared via living seeded supramolecular polymerization.
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However, in some cases, cosolvents contribute the stabilization/destabilization of supramolecular polymer. For instance, supramolecular polymerization of a hydrogen bonding porphyrin-based monomer in a hydrocarbon solvent containing a minute amount of a hydrogen bond scavenging alcohol shows distinct pathways, i.e. polymerization favored both by cooling as well as heating, and is known as “thermally bisignate supramolecular polymerization”. In another example, minute amounts of molecularly dissolved water molecules in apolar solvents, like methylcyclohexane, become part of the supramolecular polymer at lower temperatures, due to specific hydrogen bonding interaction between the monomer and water.
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The 3,4-disubstituted thiophene called ethylenedioxythiophene (EDOT) is the precursor to the polymer PEDOT. Regiochemistry is not an issue in since this monomer is symmetrical. PEDOT is found in electrochromic displays, photovoltaics, electroluminescent displays, printed wiring, and sensors.
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Via Diels-Alder reactions, it is a precursor to some commercial fragrances, including lyral, norbornene-2-carboxaldehyde, and myrac aldehyde. The monomer 3,4-epoxycyclohexylmethyl-3’,4’-epoxycyclohexane carboxylate is also produced from acrolein via the intermediacy of tetrahydrobenzaldehyde.
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The crystal structures suggests that this family of proteins plays an important role in isoprenoid quinone metabolism or in transport or storage. In both cases, the protein is a homodimer, each monomer being characterized by a lipocalin fold.
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4,4’-Oxydianiline is an organic compound with the formula O(C6H4NH2)2. It is an ether derivative of aniline. This colourless solid is a useful monomer and cross-linking agent for polymers, especially the polyimides, such as Kapton.
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The N terminal domain is a dimer. Each monomer has an alpha helical hairpin in which the two alpha helices are connected by a tight 3-residue turn. Hairpins from two monomers associate as a four-helix bundle.
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A gallotannin is any of a class of molecules belonging to the hydrolysable tannins. Gallotannins are polymers formed when gallic acid, a polyphenol monomer, esterifies and binds with the hydroxyl group of a polyol carbohydrate such as glucose.
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The most heavily practiced reaction of alkenes, dienes included, is polymerization. 1,3-Butadiene is a precursor to rubber used in tires, and isoprene is the precursor to natural rubber. Chloroprene is related but it is a synthetic monomer.
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The properties of these polyesters also is affected by the cis/trans ratio of the CHDM monomer. CHDM reduces the degree of crystallinity of PET homopolymer, improving its processability. The copolymer tends to resist degradation, e.g. to acetaldehyde.
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However, for high molecular weight polymer chains (i.e. small initiator to monomer ratio) the Mn is not easily to controlled, for some monomers, since self-condensation between monomers occurred more frequently due to the low propagating species concentration.
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Lactate dehydrogenase A (LDHA) is an enzyme which in humans is encoded by the LDHA gene. It is a monomer of Lactate dehydrogenase b, which exists as a tetramer. The other main subunit is lactate dehydrogenase B (LDHB).
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Ethyl cyanoacrylate is prepared by the condensation of formaldehyde with ethyl cyanoacetate: : + → + This exothermic reaction affords the polymer, which is subsequently sintered, thermally "cracked" to give the monomer. Alternatively, it can be prepared by the ethoxycarbonylation of cyanoacetylene.
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In step-growth polymerization, the Carothers equation (or Carothers' equation) gives the degree of polymerization, Xn, for a given fractional monomer conversion, p. There are several versions of this equation, proposed by Wallace Carothers, who invented nylon in 1935.
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1,2-Butadiene is the organic compound with the formula CH2=C=CHCH3. It is an isomer of 1,3-butadiene, a common monomer used to make synthetic rubber. It is a colorless flammable gas, one of the simplest substituted allenes.
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In Ellman's original paper, he prepared this reagent by oxidizing 2-nitro-5-chlorobenzaldehyde to the carboxylic acid, introducing the thiol via sodium sulfide, and coupling the monomer by oxidization with iodine. Today, this reagent is readily available commercially.
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Swiss Model predicts two potential protein structures, as seen in the images. The first structure predicts the protein forms a protein dimer, the second as a monomer. Rual et al. found that Fam158a interacts with a protein called TTC35.
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3D crystal structure of ornithine decarboxylase.; ; rendered via PyMOL. The active form of ornithine decarboxylase is a homodimer. Each monomer contains a barrel domain, consisting of an alpha-beta barrel, and a sheet domain, composed of two beta- sheets.
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Methyl methacrylate (MMA) is an organic compound with the formula CH2=C(CH3)COOCH3. This colorless liquid, the methyl ester of methacrylic acid (MAA), is a monomer produced on a large scale for the production of poly(methyl methacrylate) (PMMA).
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In a few microencapsulation processes, the direct polymerization of a single monomer is carried out on the particle surface. In one process, e.g. cellulose fibers are encapsulated in polyethylene while immersed in dry toluene. Usual deposition rates are about 0.5μm/min.
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Pinacolborane is the borane with the formula (CH3)4C2O2BH. It features a five- membered C2O2B ring. Owing to the presence of the alkoxide substituents, it is a monomer. It is a colorless liquid prepared by treating borane adducts with pinacol.
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Acrylic nails are made out of acrylic glass (PMMA). When it is mixed with a liquid monomer (usually ethyl methacrylate mixed with some inhibitor) it forms a malleable bead. This mixture begins to cure immediately, continuing until completely solid in minutes.
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First-generation dentin adhesives were first designed and produced in the 1950s. These systems were based on a co-monomer chelate with calcium on the surface of the tooth and generated very weak water resistant chemical bonding (2–3 MPa).
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Myosin I, a ubiquitous cellular protein, functions as monomer and functions in vesicle transport. It has a step size of 10 nm and has been implicated as being responsible for the adaptation response of the stereocilia in the inner ear.
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On-cis (green) and Off-trans (yellow) states of the chromophore. Nearby residues that move are also shown. Clockwise from the top: Arg66, Val157, Ser142, Cys-Tyr-Gly chromophore. Dronpa is 257 amino acids long and is a 28.8 kDa monomer.
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Laurolactam is an organic compound from the group of macrocyclic lactams. Laurolactam is mainly used as a monomer in engineering plastics, such as nylon-12 and copolyamides.T. Schiffer, G. Oenbrink: Cyclododecanol, Cyclododecanone, and Laurolactam. In: Ullmann's Encyclopedia of Industrial Chemistry.
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The molecular symmetry is D2h. The monomer AlBr3, observed only in the vapor, can be described as trigonal planar, D3h point group. The atomic hybridization of aluminium is often described as sp2. The Br-Al-Br bond angles are 120 °.
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Another CDC, listeriolysin O (LLO), which functions at an acidic pH, will lose its function at a neutral pH at temperatures above 30 °C, which trigger the irreversible loss of activity by the unfolding of domain 3 in the soluble monomer.
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In both cases kinetic chain length is an average quantity, as not all polymer chains in a given reaction are identical in length. The value of ν depends on the nature and concentration of both the monomer and initiator involved.
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Although polymeric sulfur reverts to its monomer at room temperature, polymers consisting mostly of sulfur can be stabilized with organic linkers such as 1,3‐diisopropenylbenzene. This process is called inverse vulcanization and produces polymers where sulfur is the main component.
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Ideal spatial parameters for topochemical polymerization Synthesis of Polydiacetylenes occurs through topochemical polymerization of 1,3-diynes. Typically, this must occur in the solid state because many diynes undergo both 1,2 and 1,4 polymerization in solution – such is the case with diiodobutadiyne, and other diynes with electron withdrawing substituents. The ideal arrangement of diynes in the solid state is a repeat distance of 5Å, a 45° tilt angle, and a 3.5Å distance between C1 of one monomer and C4 of the adjacent diyne monomer. Usually, polymerization is accompanied by a color change due to the presence of an extended π-system.
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In 1963, Ralph Hardy joined the CRD and brought Du Pont's nitrogen fixation research to international prominence with more than a hundred papers on the subject. Chemical Week called him, "one of the nation's top achievers in the dual role of scientist and scientific manager," though such managers remained common in CRD through the 1960s and 70s. Fermentation microbiology and selective genetic modification became important to the CRD development of a biological route to 1,3-propylene glycol a new monomer for making polyester. The availability of this new monomer led to the development and commercialization of Sorona, a premium polyester.
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He was elected as a Fellow of The Royal Society in 1862. Throughout the later 19th century, many chemists attempted to determine the makeup of natural rubber, with the goal of reproducing it. In 1860, Williams analyzed rubber by destructive distillation and obtained a large quantity of a light oil which he termed isoprene (polymer of the monomer isoprene—formula CH2:C(CH3)CH:CH2). Many efforts were made during the next 70 years to synthesize rubber in the laboratory by using isoprene as the monomer, but these did not bear fruit until Samuel Horne succeeded in 1955.
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Using the above assumptions, let us examine a homopolymerization reaction starting from a single monomer with z-functional groups with a fraction p of all possible bonds already having been formed. The polymer we create follows the form of a Cayley tree or Bethe lattice – known from the field of statistical mechanics. The number of branches from each node is determined by the amount of functional groups, z, on our monomer. As we follow the tree's branches we want there to always be at least one path that leads onwards, as this is the condition of an infinite network polymer.
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Unlike most vinyl polymers, PVA is not prepared by polymerization of the corresponding monomer as the monomer, vinyl alcohol, is thermodynamically unstable with respect to its tautomer acetaldehyde. Instead, PVA is prepared by hydrolysis of polyvinyl acetate, or sometimes other vinyl ester-derived polymers with formate or chloroacetate groups instead of acetate. The conversion of the polyvinyl esters is usually conducted by base-catalysed transesterification with ethanol: :[CH2CH(OAc)]n \+ C2H5OH → [CH2CH(OH)]n \+ C2H5OAc The properties of the polymer are affected by the degree of transesterification. Worldwide consumption of polyvinyl alcohol was over one million metric tons in 2006.
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In this regime, smaller particles grow faster than large ones (since larger crystals need more atoms to grow than small crystals) resulting in the size distribution focusing, yielding an improbable distribution of nearly monodispersed particles. The size focusing is optimal when the monomer concentration is kept such that the average nanocrystal size present is always slightly larger than the critical size. Over time, the monomer concentration diminishes, the critical size becomes larger than the average size present, and the distribution defocuses. Cadmium sulfide quantum dots on cells There are colloidal methods to produce many different semiconductors.
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1971 - Insulin (PDB file 1INS) is a hormone central to the metabolism of sugar and fat storage, and important in human diseases such as obesity and diabetes. It is biophysically notable for its Zn binding, its equilibrium between monomer, dimer, and hexamer states, its ability to form crystals in vivo, and its synthesis as a longer "pro" form which is then cleaved to fold up as the active 2-chain, SS-linked monomer. Insulin was a success of NASA's crystal-growth program on the space shuttle, producing bulk preparations of very uniform tiny crystals for controlled dosage.
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Due to the polysaccharides in the cell walls, F. lumbricalis is grouped with other commercially important carrageenophytes (red algae that produce carrageenans). From F. lumbricalis a polysaccharide called furcellaran (hybrid β/κ-carrageenan) can be extracted. Furcellaran is non- stoichometrically undersulphated κ-carrageenan, where every 3rd or 4th 3-linked-β-galactose monomer possesses a sulphate ester group at the 4th carbon position. For comparison, an ideal κ-carrageenan molecule would have a sulphate ester group at the 4th carbon in every 3-linked-β-galactose monomer. Furcellaran’s physical properties (gel strengths, gelling and melting temperatures) are similar to κ-carrageenan.
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The local model is used to determine the characteristics of polymerization at a section around the interface, termed the diffusion boundary layer. This model can be used to describe a system in which the monomer distribution and concentration are inhomogeneous, and is restricted to a small volume. Parameters determined using the local model include the mass transfer weight, the degree of polymerization, topology near the interface, and the molecular weight distribution of the polymer. Using local modeling, the dependence of monomer mass transfer characteristics and polymer characteristics as a function of kinetic, diffusion, and concentration factors can be analyzed.
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An addition polymer is a polymer that forms by simple linking of monomers without the co-generation of other products. Addition polymerization differs from condensation polymerization, which does co-generate a product, usually water.Introduction to Polymers 1987 R.J. Young Chapman & Hall Addition polymers can be formed by chain polymerization, when the polymer is formed by the sequential addition of monomer units to an active site in a chain reaction, or by polyaddition, when the polymer is formed by addition reactions between species of all degrees of polymerization. Addition polymers are formed by the addition of some simple monomer units repeatedly.
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Unlike K422R, H391Y showed enhanced thermal stability, stability over a range of pH values, a lesser effect of the allosteric inhibitor Phe, and resistance toward structural alteration upon binding of the activator (fructose 1,6-bisphosphate) and inhibitor (Phe). Both mutants showed a slight shift in the pH optimum from 7.4 to 7.0. The co-expression of homotetrameric wild type and mutant PKM2 in the cellular milieu resulting in the interaction between the two at the monomer level was substantiated further by in vitro experiments. The cross-monomer interaction significantly altered the oligomeric state of PKM2 by favoring dimerisation and heterotetramerization.
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The first synthetic soil conditioners were introduced in the 1950s, when the chemical hydrolysed polyacrylonitrile was the most used. Because of their ability to absorb several hundred times their own weight in water, polyacrylamides and polymethacrylates (also known as hydroabsorbent polymers, superabsorbent polymers or hydrogels) were tested in agriculture, horticulture and landscaping beginning in the 1960s. Interest disappeared when experiments proved them to be phytotoxic due to their high acrylamide monomer residue. Although manufacturing advances later brought the monomer concentration down below the toxic level, scientific literature shows few successes in utilizing these polymers for increasing plant quality or survival.
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Insect olfactory receptors (also known as odorant receptors, ORs) are expressed in the cell membranes of the olfactory sensory neurons of insects. Similarly to mammalian olfactory receptors, in insects each olfactory sensory neuron expresses one type of OR, allowing the specific detection of a volatile chemical. Differently to mammalian ORs, insect ORs form a heteromer with a fixed monomer, Orco, and a variable OR monomer, which confers the odour specificity. Insect ORs are transmembrane proteins with seven transmembrane helices similarly to G protein coupled receptors, but they have the reverse topology with an intracellular N-terminal and an extracellular C-terminal instead.
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Propagation: Propagating radical chains of length n in their active (radical) form, Pn•, add to monomer, M, to form longer propagating radicals, Pn+1•. RAFT pre-equilibrium: A polymeric radical with n monomer units (Pn) reacts with the RAFT agent to form a RAFT adduct radical. This may undergo a fragmentation reaction in either direction to yield either the starting species or a radical (R•) and a polymeric RAFT agent (S=C(Z)S-Pn). This is a reversible step in which the intermediate RAFT adduct radical is capable of losing either the R group (R•) or the polymeric species (Pn•).
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CXCL1 exists as both monomer and dimer and both forms are able to bind chemokine receptor CXCR2. However, CXCL1 chemokine is able to dimerize only at higher (micromolar) concentrations and its concentrations are only nanomolar or picomolar upon normal conditions, which means that the form of WT CXCL1 is more likely monomeric while dimeric CXCL1 is present only during infection or injury. CXCL1 monomer consists of three antiparallel β-strands followed by C- terminal α-helix and this α-helix together with the first β-strand are involved in forming a dimeric globular structure. Upon normal conditions, CXCL1 is not expressed constitutively.
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However, to realize a covalent analogue of chain-growth supramolecular polymerization, a challenging prerequisite is the design of appropriate monomers that can polymerize only by the action of initiators. Recently one example of chain-growth supramolecular polymerization with “living” characteristics is demonstrated. In this case, a bowl-shaped monomer with amide-appended side chains form a kinetically favored intramolecular hydrogen bonding network and does not spontaneously undergo supramolecular polymerization at ambient temperatures. However, an N-methylated version of the monomer serves as an initiator by opening the intramolecular hydrogen bonding network for the supramolecular polymerization, just like ring-opening covalent polymerization.
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Stereochemical information of a chiral monomer can be expressed in a supramolecular polymer. Helical supramolecular polymer with P-and M-conformation are widely seen, especially those composed of disc-shaped monomers. When the monomers are achiral, both P-and M-helices are formed in equal amounts. When the monomers are chiral, typically due to the presence of one or more stereocenters in the side chains, the diastereomeric relationship between P-and M-helices leads to the preference of one conformation over the other. Typical example is a C3-symmetric disk-shaped chiral monomer that forms helical supramolecular polymers via the “majority rule”.
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Additionally, an insert domain (ID, residues 638-756) resides within FnIII-2, containing the α/β furin cleavage site, from which proteolysis results in both IDα and IDβ domains. Within the β-chain, downstream of the FnIII-3 domain lies a transmembrane helix (TH) and intracellular juxtamembrane (JM) region, just upstream of the intracellular tyrosine kinase (TK) catalytic domain, responsible for subsequent intracellular signaling pathways. Upon cleavage of the monomer to its respective α- and β-chains, receptor hetero or homo- dimerisation is maintained covalently between chains by a single disulphide link and between monomers in the dimer by two disulphide links extending from each α-chain. The overall 3D ectodomain structure, possessing four ligand binding sites, resembles an inverted 'V', with the each monomer rotated approximately 2-fold about an axis running parallel to the inverted 'V' and L2 and FnIII-1 domains from each monomer forming the inverted 'V's apex.
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Caprolactone is prepared industrially by Baeyer-Villiger oxidation of cyclohexanone with peracetic acid. Caprolactone is a monomer used in the production of highly specialised polymers. Ring-opening polymerization, for example, gives polycaprolactone. Another polymer is polyglecaprone, used as suture material in surgery.
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Similarly, thiophene is not a monomer as such. The rings are linked through the 2- and 5-positions. Poly(alkylthiophene)s have substituents at the 3- or 4-position. They are also white solids, but tend to be soluble in organic solvents.
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Supramolecular polymers are composed of monomers that interact non-covalently. Common interactions include hydrogen bonds, metal coordination, and van der Waals forces. Mechanical stress in supramolecular polymers causes the disruption of these specific non-covalent interactions, leading to monomer separation and polymer breakdown.
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A study by Zeng and Lee investigated the role of the initiator in the in situ polymerization process of clay nanocomposites. One of the major findings was that the more favorable nanocomposite product was produced with a more polar monomer and initiator.
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2-Ethyl-2-oxazoline (EtOx) is an oxazoline which is used particularly as a monomer for the cationic ring-opening polymerization to poly(2-alkyloxazoline)s. This type of polymers are under investigation as readily water-soluble and biocompatible materials for biomedical applications.
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Endostatin monomer, basic amino acid residues shown in red (source: pdb.org, 1KOE). Endostatin is a naturally occurring, 20-kDa C-terminal fragment derived from type XVIII collagen. It is reported to serve as an anti-angiogenic agent, similar to angiostatin and thrombospondin.
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Similar to Taipoxin are toxins with different subunits of the PLA domains: Notexin is a monomer from Notechis scutatus venom, β-bungarotoxin is a heterodimer from Chinese banded krait (Bungarus multicinctus) venom, and textilotoxin is a pentamer from eastern Pseudonaja textilis venom.
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The CRP gene is located on chromosome 1 (1q23.2). It is a member of the small pentraxins family. The monomer has 224 amino acids, and molecular mass of 25,106 Da. In serum, it assembles into stable pentameric structure with a discoid shape.
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The monomer is typically made from fermented plant starch such as from corn, cassava, sugarcane or sugar beet pulp. Several industrial routes afford usable (i.e. high molecular weight) PLA. Two main monomers are used: lactic acid, and the cyclic di-ester, lactide.
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TfR1 = transferrin receptor 1 in Human iron metabolism. TfR1 is a transmembrane glycoprotein composed of two disulfide-linked monomers joined by two disulfide bonds. Each monomer binds one holo-transferrin molecule creating an iron-Tf-TfR complex which enters the cell by endocytosis.
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Because a monomer of buk2 is about 43kDa, it was believed that the enzyme itself was either an octomer or a nonamer. Investigators hypothesized that the enzyme was an octomer since most of the proteins within the ASHKA super family form dimers.
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The knowledge of human ClpX protein are majorly based on the investigations on E. Coli protein. The monomer of ClpX protein in E. Coli contains a N-terminal domain and a AAA+ module which consists of a large and a small AAA+ domain.
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Ozone decomposition in water studied by pulse radiolysis. 2. OH and HO4 as Chain Intermediates J. Staehelin et al., J. Phys. Chem. (1984) 88, 5999-6004 In chain-growth polymerization the propagation step is the addition of a monomer to the growing chain.
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In step-growth polymerization (condensation reaction) small molecules are eliminated, which are also contributing to shrinkage when removed. At elevated temperatures also the thermal aging plays a role, where unreacted monomer can polymerize and degradation products and other small molecules are released.
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Sequence-defined polymer (Syn. sequence-specific polymer, sequence-ordered polymer) is a uniform macromolecule with an exact chain-length and a perfectly defined sequence of monomers. In other words, each monomer unit is at a defined position in the chain e.g. peptides, proteins, oligonucleotides.
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In E. coli, the IIBChb is a monomer. Two IIBChb monomers associate with the IIAChb dimer. The structure of the IIB domain of the Chb porter has been determined both by NMR and by X-ray crystallography. It exhibits an α/β doubly wound superfold.
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The bridge is synthetically incorporated at the 2', 4'-position of the ribose to afford a 2', 4'-BNA monomer. The monomers can be incorporated into oligonucleotide polymeric structures using standard phosphoamidite chemistry. BNAs are structurally rigid oligo-nucleotides with increased binding affinities and stability.
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Space-filling model of lysophosphatidic acid phosphatase depicting the filled solvent channel. Image generated from 4JOC.; Lysophosphatidic acid phosphatase is a monomer composed of two domains. One domain functions as a cap on the enzyme, while the second comprises the body of the enzyme.
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General monomer of polysilanes, where the R's are the same or different organic groups. Polysilanes are organosilicon compounds with the formula (R2Si)n. They are relatives of traditional organic polymers but their backbones are composed of silicon atoms. They exhibit distinctive optical and electrical properties.
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Dimethylaminoethyl acrylate (2-dimethylaminoethyl acrylate) or DMAEA is an unsaturated carboxylic acid ester having a tertiary amino group. It is a colorless to yellowish, water-miscible liquid with a pungent, amine-like odor. DMAEA is an important acrylic monomer that gives basic properties to copolymers.
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The monomer was prepared via 2,2,6,6-tetramethyl-4-piperidinol (1) and methacryloyl chloride. The precursor neutral polymer (3) was oxidized to the stable radical polymer (4) by 3-chloroperoxybenzoic acid (mCPBA).Kurosaki, T.; Lee, K. W.; Okawara, M. J. Polym. Sci. A-1 Polym. Chem.
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In biochemistry, a ribonucleotide is a nucleotide containing ribose as its pentose component. It is considered a molecular precursor of nucleic acids. Nucleotides are the basic building blocks of DNA and RNA. The monomer itself from ribonucleotides forms the basic building blocks for RNA.
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Vinyl acetate is a commercially important monomer that is classified as a vinyl ester (i.e. an ester of vinyl alcohol). Vinyl ester refers to esters formerly derived from vinyl alcohol. Commercially important examples of these monomers are vinyl acetate, vinyl propionate, and vinyl laurate.
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Exaggerated ligand binding results such as SDZ GLC 756 (as used in the figure) were explained by reference to this monomer-dimer equilibrium. According to Seeman, "...Numerous postmortem studies have consistently revealed D2 receptors to be elevated in the striata of patients with schizophrenia".
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Rapid Commun. 2015, 36, 151–158. Room Temperature Synthesis of a Covalent Monolayer Sheet at Air/Water Interface Using a Shape- Persistent Photoreactive Amphiphilic Monomer; Y. Chen, M. Li, P. Payamyar, Z. Zheng, J. Sakamoto, A. D. Schlüter, ACS Macro Letters 2014, 3, 153–158.
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Calcium ions (yellow) are also shown. Based on the PyMOL rendering of PDB 1UEA. For simplicity, the other MMP-3 monomer complexed with its respective TIMP-1 is not shown. The catalytic domain of MMP-3 can be inhibited by tissue inhibitors of metalloproteinases (TIMPs).
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For example, 2K reactive mixture can use low molecular weight monomer, oligomer, and functionalized low molecular polymer to make final cross-linked high molecular weight polymer. 2K aerosol can increase solid contents and deliver high performance polymer products, such as curable paints, foams, and adhesives.
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The actin monomer has two asymmetric domains; the larger inner domain comprised by sub-domains 3 and 4, and the smaller outer domain by sub-domains 1 and 2. Both the amino and carboxy- termini lie in sub-domain 1 of the outer domain.
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4-Vinylanisole is an organic compound with the formula CH3OC6H4CH=CH2. It is one of three isomers of vinylanisole. A colorless liquid, 4-vinylanisole is found in a number of foods and drinks. It is also a monomer for the synthesis of modified polystyrenes.
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Nitrosobenzene is the organic compound with the formula C6H5NO. It is one of the prototypical organic nitroso compounds. Characteristic of its functional group, it is a dark green species that exists in equilibrium with its pale yellow dimer. Both monomer and dimer are diamagnetic.
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Control of monomer assembly through covalent assembly has also been demonstrated using covalent interactions with porphyrins. Upon thermal activation of porphyrin building blocks, covalent bonds form to create a conductive polymer, a versatile route for bottom-up construction of electronic circuits has been demonstrated.
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The IFNγ monomer consists of a core of six α-helices and an extended unfolded sequence in the C-terminal region.; This is shown in the structural models below. The α-helices in the core of the structure are numbered 1 to 6. Figure 1.
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In both Alteromonas carrageenovora and Pseudoalteromonas sp. CL19, lambda-carrageenase is encoded by the cglA gene. The product of this gene is a protein consisting of 942 amino acids, this protein includes a 25 amino acid signal peptide. Lambda-carrageenase is found as a monomer.
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PTGS2 (COX-2), converts arachidonic acid (AA) to prostaglandin endoperoxide H2. PGHSs are targets for NSAIDs and PTGS2 (COX-2) specific inhibitors called coxibs. PGHS-2 is a sequence homodimer. Each monomer of the enzyme has a peroxidase and a PTGS (COX) active site.
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Usually ionomer synthesis consists of two steps – the introduction of acid groups to the polymer backbone and the neutralization of some of the acid groups by a metal cation. In very rare cases, the groups introduced are already neutralized by a metal cation. The first step (introduction of acid groups) can be done in two ways; a neutral non-ionic monomer can be copolymerized with a monomer that contains pendant acid groups or acid groups can be added to a non-ionic polymer through post- reaction modifications. For example, ethylene-methacrylic acid and sulfonated perfluorocarbon (Nafion) are synthesized through copolymerization while polystyrene sulfonate is synthesized through post-reaction modifications.
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In polymer chemistry, there are several mechanisms by which a polymerization reaction can terminate depending on the mechanism and circumstances of the reaction. A method of termination that applies to all polymer reactions is the depletion of monomer. In chain growth polymerization, two growing chains can collide head to head causing the growth of both of the chains to stop. In the case of radical or anionic polymerization, chain transfer can occur where the radical at the end of the growing chain can be transferred from the chain to an individual monomer unit causing a new chain to start growing and the previous chain to stop growing.
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Lipid II is the final intermediate in peptidoglycan synthesis. It is formed when the MurG transferase catalyzes addition of N-acetylglucosamine (GlcNAc) to Lipid I, resulting in a complete disaccharide-pentapeptide monomer with a bactoprenol-pyrophosphate anchor. This occurs on the inside of the cytoplasmic membrane, where the bactoprenol chain is embedded in the inner leaflet of the bilayer. Lipid II is then transported across the membrane by a flippase, to expose the disaccharide-pentapeptide monomer, which is the pentapeptide stem consisting of L-Ala-γ-D-Glu-m-DAP-D-Ala-D-Ala between GlcNAc and N-acetylmuramic acid (MurNAc), for polymerization and cross-linking into peptidoglycan.
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Acrylated epoxy oligomer The monomers used in radiation curable systems help control the speed of cure, crosslink density, final surface properties of the film, and viscosity of the resin. Examples of monomers include styrene, N-Vinylpyrrolidone, and acrylates. Styrene is a low cost monomer and provides a fast cure, N-vinylpyrrolidone results in a material that is highly flexible when cured, has low toxicity, and acrylates are highly reactive, allowing for rapid cure rates, and are highly versatile with monomer functionality ranging from monofunctional to tetrafunctional. Like oligomers, several types of monomers can be employed to achieve the desirable properties of the final material.
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The structure they solved was of a non-membrane bound pre-pore, the conformation of the heptamer before the complex extends a β-barrel through the plasma membrane to shuttle the LF and EF into the cytosol. Heptamerization and pore formation is sterically hindered by the PA20 fragment, but when it is removed from the top of the monomer, the pre-pore is quickly formed. The heptamer formation causes no major changes in the conformation of each individual monomer, but by coming together, more than 15400 Ų (154 nm2) of protein surface is buried. This buried surface consists mostly of polar or charged side groups from domains 1 and 2.
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HoloEnzyme: The holoenzyme SDH contains 319 residues, 1 PLP cofactor molecule, and 131 water molecules. The overall fold of the monomer is very similar to that of other PLP-dependent enzymes of the Beta-family. The enzyme contains a large domain (catalytic domain or PLP- binding domain) and a small domain. The domains are joined by two peptide linkers (residues 32-35 and 138-146), with the internal gap created being the space for the active site (Figure 1). File:LargeandSmallDomainSDH.jpg Figure 1 shows the large catalytic domain in purple and cyan and the small regulatory domain in green in a monomer of Serine Dehydratase.
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The properties of PP are strongly affected by its tacticity, the orientation of the methyl groups ( in the figure) relative to the methyl groups in neighboring monomer units. A Ziegler–Natta catalyst is able to restrict linking of monomer molecules to a specific orientation, either isotactic, when all methyl groups are positioned at the same side with respect to the backbone of the polymer chain, or syndiotactic, when the positions of the methyl groups alternate. Commercially available isotactic polypropylene is made with two types of Ziegler-Natta catalysts. The first group of the catalysts encompasses solid (mostly supported) catalysts and certain types of soluble metallocene catalysts.
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ANT has long been thought to function as a homodimer, but this concept was challenged by the projection structure of the yeast Aac3p solved by electron crystallography, which showed that the protein was three-fold symmetric and monomeric, with the translocation pathway for the substrate through the centre. The atomic structure of the bovine ANT confirmed this notion, and provided the first structural fold of a mitochondrial carrier. Further work has demonstrated that ANT is a monomer in detergents and functions as a monomer in mitochondrial membranes. ADP/ATP translocase 1 is the major AAC in human cells and the archetypal protein of this family.
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Catalyst transfer polycondensation (CTP) is a chain-growth polycondensation mechanism in which the monomers do not directly react with one another and instead the monomer will only react with the polymer end group through a catalyst-mediated mechanism. The general process consists of the catalyst activating the polymer end group followed by a reaction of the end group with a 2nd incoming monomer. The catalyst is then transferred to the elongated chain while activating the end group (as shown below). 600px Catalyst transfer polycondensation allows for the living polymerization of π-conjugated polymers and was discovered by Tsutomu Yokozawa in 2004 and Richard McCullough.
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In common usage, the prefix "PA" (polyamide) or the name "Nylon" are used interchangeably and are equivalent in meaning. The nomenclature used for nylon polymers was devised during the synthesis of the first simple aliphatic nylons and uses numbers to describe the number of carbons in each monomer unit, including the carbon(s) of the carboxylic acid(s). Subsequent use of cyclic and aromatic monomers required the use of letters or sets of letters. One number after "PA" or "Nylon" indicates a homopolymer which is monadic or based on one amino acid (minus H2O) as monomer: :PA 6 or Nylon 6: [NH−(CH2)5−CO]n made from ε-Caprolactam.
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In its monomeric form, zinc pyrithione has two of the anions chelated to a zinc centre with a tetrahedral geometry. In the solid state, it forms a dimer in which each zinc centre adopts a trigonal bipyramidal geometry with two of the anions acting as bridging ligands coordinated through the oxygen atoms in the axial positions. In solution, the dimers dissociate via scission of zinc- oxygen bonds to each bridging ligand. Further dissociation of the monomer into its constituents can occur and is undesirable as the complex is more potent in medical applications; for this reason, zinc carbonate can be added to formulations as it inhibits the monomer dissociation.
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Researchers identified a number of splice variants of IL-24 lacking one or more exons. The signal peptide in IL-24 is two times the length as in other related human cytokines (51 amino acids), and the predicted molecular mass of IL-24 monomer is 18.3 kDa.
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A related chemical compound, is the more stable chromium(II) hydride, identified by Weltner et al. in 1979 using a solid argon matrix. This compound is susceptible to dimerisation in the gas phase. The dimer is more stable than the monomer by 121 kJ mol−1.
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Cartilage KSII is almost entirely sulphated, consisting of disulphated monomers interrupted occasionally by a single monosulphated lactosamine monomer. Fucosylation is also common with alpha-linked fucose present at the carbon 3 position of sulphated GlcNAc, except in the case of tracheal KSII where this feature is absent.
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In the resin and in the cured polyfurfurol, the furan rings are not connected by conjugation. The resins are generally used as binders for sand castings. The furan monomer is typically converted to a free-flowing resin with mild acid catalysis. Curing is achieved using strong acid.
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Many peroxomolybdates are known. They tend to form upon treatment of molybdate salts with hydrogen peroxide. Notable is the monomer–dimer equilibrium [Mo2O3(O2)2(H2O)2]2− [Mo2O3(O2)4(H2O)2]2−. Also known but unstable is [Mo(O2)4]2− (see potassium tetraperoxochromate(V)).
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This structure renders the polymers produced from it, very resistant to alkali degradation as there is no hydrogen (thus proton producing species) on the α-carbon. They have good resistance to degradation from ultraviolet light. The monomer has even been used to produce vibration dampening resins.
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This treatment gives the close bonding of tire cord to rubber. 2-Vinylpyridine is a co-monomer for acrylic fibers. Between 1–5% of copolymerized 2-vinylpyridine provide the reactive sites for dyes.Bönnemann, H.; Brijoux, W.. Transition Metals for Organic Synthesis: Building Blocks and Fine Chemicals.
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Hexafluoroacetone is used in the production of hexafluoroisopropanol: :(CF3)2CO + H2 → (CF3)2CHOH It is also used as a precursor to hexafluoroisobutylene, a monomer used in polymer chemistry, and as a building block in the synthesis of midaflur, bisphenol AF, 4,4′-(hexafluoroisopropylidene)diphthalic anhydride, and alitame.
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Caspase-activated DNase (CAD) or DNA fragmentation factor subunit beta is a protein that in humans is encoded by the DFFB gene. It breaks up the DNA during apoptosis and promotes cell differentiation. It is usually an inactive monomer inhibited by ICAD. This is cleaved before dimerization.
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The nitroso group has both a +M and -M effect, but the -M effect is more favorable. Nitrogen has a lone pair of electrons. However, the lone pair of its monomer form is unfavourable to donate through resonance. Only the dimer form is available for +M effect.
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This is also called trifluoroboroxin. The trimer is the predominant form in gas at 1000K. When heated to 1200K it mostly converts to the monomer BFO. Boron oxyfluoride can be condensed from vapour to a fluorine deficient glass at temperatures below 190° by very rapid cooling.
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This means that aside to the regular mixing entropy there is another entropic contribution from the interaction between solvent and monomer. This contribution is sometimes very important in order to make quantitative predictions of thermodynamic properties. More advanced solution theories exist, such as the Flory–Krigbaum theory.
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Derivatization of the PFCA ring. Under favorable conditions, a good nucleophile can replace all the fluorine atoms on PFCA ring (Scheme 2). Scheme 2. Multi-substitution on PFCA ring PFCAs have a huge potential to be used as a monomer to produce a variety of polymers.
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Acetic acid is a chemical reagent for the production of chemical compounds. The largest single use of acetic acid is in the production of vinyl acetate monomer, closely followed by acetic anhydride and ester production. The volume of acetic acid used in vinegar is comparatively small.
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Trimethylhexamethylenediamine is the name used to refer to a mixture of two isomers of trimethyl-1,6-hexanediamine. The mixture is used as a monomer in nylon TMDT. It is available commercially under the trade name Vestamin TMD from the company Evonik Industries. Trimethylhexamethylenediamine is synthesized from isophorone.
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An example is the 2019 explosion of the tanker Stolt Groenland; in this incident 5,250 metric tons of styrene monomer detonated while the ship was docked in Ulsan, Republic of Korea. The autopolymerisation reaction can only be kept in check by the continuous addition of polymerisation inhibitors.
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Polymerization can be performed in large range of solvents (including water), within a wide temperature range, high functional group tolerance and absence metals for polymerization. As of 2014, the range of commercially available RAFT agents covers close to all the monomer classes that can undergo radical polymerization.
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Ethyl vinyl ether is an organic compound with the chemical formula CH3CH2OCH=CH2. It is the simplest enol ether that is liquid at room temperature. It is used as a synthetic building block and a monomer. Use of ethyl vinyl ether in the synthesis of glutaraldehyde.
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In computational biology, a polymer or oligomer of a known size is called a k-mer instead of an n-gram, with specific names using Greek numerical prefixes such as "monomer", "dimer", "trimer", "tetramer", "pentamer", etc., or English cardinal numbers, "one- mer", "two-mer", "three-mer", etc.
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Methyl 2-chloroacrylate is a colorless liquid used in manufacture of acrylic high polymer similar to polymethylmethacrylate. It is also used as a monomer for certain specialty polymers. Methyl 2-chloroacrylate is polymerizable, insoluble in water, and a skin, eye, and lung irritant. Inhalation of vapors causes pulmonary edema.
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Diphenyl carbonate is the organic compound with the formula (C6H5O)2CO. It is classified as an acyclic carbonate ester. It is a colorless solid. It is both a monomer in combination with bisphenol A in the production of polycarbonate polymers and a product of the decomposition of polycarbonates.
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A powder and liquid are mixed together to form the luting cement. The powder contains fluoroaluminosilicate glass particles, sodium fluoride, and self-cured and light-cured initiators. The liquid contains poly-acid modified monomers and water. The carboxylic acid groups in the methacrylate-carboxylic acid monomer help with adhesion.
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The result of the charge transfer facilitates ring slippage and the mesitylene group changes from η to η this allows the phenylacetylene monomer units to bind to the metal centre. Recently, it has been reported that tricarbonyl(mesitylene)molybdenum can act as a catalyst for the epoxidation of alkenes.
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Dimeric form of CTP synthase from Sulfolobus solfataricus (PDB code: 3NVA). Chain A is depicted in blue and Chain B in green. Active CTP synthase exists as a homotetrameric enzyme. At low enzyme concentrations and in the absence of ATP and UTP, CTP synthase exists as inactive monomer.
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The viscosity of polymer solutions is a valued parameter. Viscometers such as this are employed in such measurements. Polymers are high molecular mass compounds formed by polymerization of monomers. The simple reactive molecule from which the repeating structural units of a polymer are derived is called a monomer.
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This octamer can be thought of as a tetramer of dimers, and it is likely that the dimer is the active unit of the protein. In each dimer, an arginine residue Arg20 forms part of the active site in the other monomer, where it helps bind both phosphate groups.
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1,2-Dimethyldiborane is an easily condensed, colorless gas that ignites spontaneously in air. An isomer of 1,2-dimethyldiborane is 1,1-dimethyldiborane, known as unsymmetrical dimethyldiborane, which has two methyl groups on one boron atom. Other methylated versions of diborane including methyldiborane, trimethyldiborane, tetramethyldiborane. Trimethylborane exists as a monomer.
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This gene encodes apolipoprotein (apo-) A-II, which is the second most abundant protein of the high density lipoprotein particles. The protein is found in plasma as a monomer, homodimer, or heterodimer with apolipoprotein D. Defects in this gene may result in apolipoprotein A-II deficiency or hypercholesterolemia.
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The co-monomer is typically dioxolane, but ethylene oxide can also be used. Dioxolane is formed by reaction of ethylene glycol with aqueous formaldehyde over an acid catalyst. Other diols can also be used. Trioxane and dioxolane are polymerized using an acid catalyst, often boron trifluoride etherate, BF3OEt2.
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The crystal structure of the glyoxylate reductase enzyme from the hyperthermophilic archeon Pyrococcus horiskoshii OT3 has been reported. The enzyme exists in the dimeric form. Each monomer has two domains: a substrate- binding domain where glyoxylate binds, and a nucleotide-binding domain where the NAD(P)H cofactor binds.
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Heating or irradiation with UV light regenerates the ketene monomer: :(C2H2O)2 2 CH2CO Alkylated ketenes also dimerize with ease and form substituted diketenes. Diketene readily hydrolyzes in water forming acetoacetic acid. Its half-life in water is approximately 45 min. a 25 °C at 2 < pH < 7.
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The detyrosynating activity was first identified in the late 1970s. It is a slow acting enzyme that uses polymeric tubulin as a substrate. As a result, only stabilized microtubules accumulate this particular modification. Tubulin detyrosination is reversed by the tubulin- tyrosine ligase, which acts only on alpha-tubulin monomer.
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Leuco-fisetinidin is a flavan-3,4-diol (leucoanthocyanidin), a type of natural phenolic substance. It is the monomer of condensed tannins called profisetinidins. Those tannins can be extracted from the heartwood of Acacia mearnsii or from the heartwoods of Schinopsis balansae, Schinopsis quebrachocolorado and from commercial quebracho extract.
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The structure of insulin. The left side is a space-filling model of the insulin monomer, believed to be biologically active. Carbon is green, hydrogen white, oxygen red, and nitrogen blue. On the right side is a ribbon diagram of the insulin hexamer, believed to be the stored form.
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In humans, septins are involved in cytokinesis, cilium formation and neurogenesis through the capability to recruit other proteins or serve as a diffusion barrier. There are 13 different human genes coding for septins. The septin proteins produced by these genes are grouped into four subfamilies each named after its founding member: (i) SEPT2 (SEPT1, SEPT4, SEPT5), (ii) SEPT3 (SEPT9, SEPT12), (iii) SEPT6 (SEPT8, SEPT10, SEPT11, SEPT14), and (iv) SEPT7. Septin protein complexes are assembled to form either hetero-hexamers (incorporating monomers selected from three different groups and the monomer from each group is present in two copies; 3 x 2 = 6) or hetero-octamers (monomers from four different groups, each monomer present in two copies; 4 x 2 = 8).
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EM reconstruction of a Pneumolysin pre- pore α-helices that unwind and pierce the membrane are in pink. () CDCs, such as pneumolysin, from S. pneumoniae, form pores as large as 260Å (26 nm), containing between 30 and 44 monomer units. Electron microscopy studies of pneumolysin show that it assembles into large multimeric peripheral membrane complexes before undergoing a conformational change in which a group of α-helices in each monomer change into extended, amphipathic β-hairpins that span the membrane, in a manner reminiscent of α-haemolysin, albeit on a much larger scale (Fig 3). CDCs are homologous to the MACPF family of pore-forming toxins, and it is suggested that both families use a common mechanism (Fig 4).
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In polymer science, precipitation polymerization is a heterogeneous polymerization process that begins initially as a homogeneous system in the continuous phase, where the monomer and initiator are completely soluble, but upon initiation the formed polymer is insoluble and thus precipitates. After precipitation, the polymerization proceeds by absorption of monomer and initiator into the polymer particles.George Odian in Principles of Polymerization third edition, John Wiley and Sons, 1991, pp 302 A distinction should be made between precipitation and dispersion polymerization, due to the similarities. A dispersion polymerization is actually a type of precipitation polymerization, but the difference lies in the fact that precipitation polymerizations give larger and less regular particles, as a result of little or no stabilizer present.
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Galactose oxidase contains 639 amino acids. It is a single peptide monomer that has three β-structural domains. Domain 1 (residues 1-155) is a β-sandwich consisting of eight antiparallel β-strands. It contains a possible binding site for Na+ or Ca2+, which may serve structural roles in the protein.
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PIDA, monomer, and host scaffolds used. Applications utilizing properties of conjugated polymers emerged from work done by Heeger, McDiaramid, and Shirakawa with the discovery that polyacetylene is a conducting, albeit difficult to process material. Since then, work has been done to mimic this conjugated polymer’s backbone (e.g., poly(p-phenylenevinylene)).
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The compound is exclusively a monomer in the gas phase. In the gas phase it adopts D3h symmetric trigonal bipyramidal geometry as indicated by electron diffraction. As a solid, VF5 forms a polymeric structure with fluoride-bridged octahedral vanadium centers. The formation enthalpy of VF5 is -1429.4 ± 0.8 kJ/mol.
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Polyvinylcarbazole (PVK) is a temperature-resistantHans-Dieter Jakubke, Ruth Karcher (Koordinatoren): Lexikon der Chemie in drei Bänden, Spektrum Verlag, Band 3, Heidelberg 1999, , S. 92. thermoplastic polymer produced by radical polymerization from the monomer N-vinylcarbazole. It is photoconductive and thus the basis for photorefractive polymers and organic light-emitting diodes..
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231x231px CW occurs after the polymer chain has grown somewhat on the metal catalyst. The precursor is a 16 e− complex with the general formula [ML2(C2H4)(chain)]+. The ethylene ligand (the monomer) dissociates to produce a highly unsaturated 14 e− cation. This cation is stabilized by an agostic interaction.
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Phosphoglucomutase () is an enzyme that transfers a phosphate group on an α-D- glucose monomer from the 1' to the 6' position in the forward direction or the 6' to the 1' position in the reverse direction. More precisely, it facilitates the interconversion of glucose 1-phosphate and glucose 6-phosphate.
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One of the monomers binds araI1, the remaining monomer binds araI2 \- in other words, binding of AraC to araI2 is allosterically induced by arabinose. One of the AraC monomers places near to the araBAD promoter in this configuration, which helps to recruit RNA polymerase to the promoter to initiate transcription.
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HA is a homotrimeric integral membrane glycoprotein. It is shaped like a cylinder, and is approximately 13.5 nanometres long. HA trimer is made of three identical monomers. Each monomer is made of an intact HA0 single polypeptide chain with HA1 and HA2 regions that are linked by 2 disulfide bridges.
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What is referred to as bone cement implantation syndrome (BCIS) is described in the literature.Br. J. Anaesth. (2009) 102 (1): 12-22. doi: 10.1093/bja/aen328 For a long time it was believed that the incompletely converted monomer released from bone cement was the cause of circulation reactions and embolism.
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Anchorage without cement - cement-free implant placement - is the alternative. New bone cement formulations require characterization according to ASTM F451.ASTM F451: Standard Specification for Acrylic Bone Cement This standard describes the test methods to assess cure rate, residual monomer, mechanical strength, benzoyl peroxide concentration, and heat evolution during cure.
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Human PKM2 monomer has 531 amino acids and is a single chain divided into A, B and C domains. The difference in amino acid sequence between PKM1 and PKM2 allows PKM2 to be allosterically regulated by FBP and for it to form dimers and tetramers while PKM1 can only form tetramers.
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In polymer chemistry, a structural unit is a building block of a polymer chain. It is the result of a monomer which has been polymerized into a long chain. There may be more than one structural unit in the repeat unit. When different monomers are polymerized, a copolymer is formed.
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The ring-opening polymerization of butyrolactone gives polybutyrolactone. The resulting reverts to the monomer by thermal cracking. It is claimed that poly(GBL) is competitive with commercial biomaterial poly(4-hydroxybutyrate), or P4HB. It is further claimed that poly(GBL) is cheaper to make than P4HB, although both are bio-derived.
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Galectins essentially bind to glycans featuring galactose and its derivatives. However, physiologically, they are likely to require lactose or N-aceyllactosamine for significantly strong binding. Generally, the longer the sugar the stronger the interactions. For example, galectin-9 binds to polylactosamine chains with stronger affinity than to an N-acetyllactosamine monomer.
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Another type of drug delivery vehicle used is polymeric micelles. They are prepared from certain amphiphilic co-polymers consisting of both hydrophilic and hydrophobic monomer units. They can be used to carry drugs that have poor solubility. This method offers little in the terms of size control or function malleability.
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Pillar[6]arene can be targeted as the major product of the Friedel-Crafts cyclooligomerization by using bulky alkoxy groups on the monomer, switching the Lewis acid catalyst Synthesis and host–guest properties of pillar[6]arenes. Sci. China Chem. 2012, 55, 223-228. or by using a bulky chlorinated solvent.
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PVDF may be synthesized from the gaseous vinylidene fluoride (VDF) monomer by a free- radical (or controlled-radical) polymerization process. This may be followed by processes such as melt casting, or processing from a solution (e.g. solution casting, spin coating, and film casting). Langmuir–Blodgett films have also been made.
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Unreacted monomer can be removed from unexposed regions, leaving a relief polymeric image. Several forms of 3D printing—including layer-by-layer stereolithography and two-photon absorption 3D photopolymerization—use photopolymerization. Multiphoton polymerization using single pulses have also been demonstrated for fabrication of complex structures using a digital micromirror device.
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High ultraviolet transmission is a hallmark of COC materials, with optimized grades the leading polymer alternatives to quartz glass in analytical and diagnostic applications. Some properties will vary due to monomer content. These include glass transition temperature, viscosity, and stiffness. The glass transition temperature of these polymers can exceed 200°C.
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91–95 °C), It is estimated that, at concentrations less than 1 M, glyoxal exists predominantly as the monomer or hydrates thereof, i.e., OCHCHO, OCHCH(OH)2, or (HO)2CHCH(OH)2. At concentrations above 1 M, dimers predominate. These dimers are probably dioxolanes, with the formula [(HO)CH]2O2CHCHO.
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Pd-Ag dimeric transition state vs Pd monomer transition state for meta-selective C–H activation The role of mono-N-protected amino acid is proposed as a dianionic ligand which participates in the CMD step assisting the deprotonation of the C–H bond in the rate- and regio-determining step.
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It inhibits cell movement and induces nuclear extrusion. Cytochalasin B shortens actin filaments by blocking monomer addition at the fast-growing end of polymers. Cytochalasin B inhibits glucose transport and platelet aggregation. It blocks adenosine-induced apoptotic body formation without affecting activation of endogenous ADP-ribosylation in leukemia HL-60 cells.
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The Flory-Stockmayer Theory allows for the prediction of when gelation occurs using percent conversion of initial monomer and is not confined to cases of stoichiometric balance. Additionally, the Flory-Stockmayer Theory can be used to predict whether gelation is possible through analyzing the limiting reagent of the step-growth polymerization.
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The P2 protein can interact with P0 and P1 to form a pentameric complex consisting of P1 and P2 dimers, and a P0 monomer. The protein is located in the cytoplasm. As is typical for genes encoding ribosomal proteins, there are multiple processed pseudogenes of this gene dispersed through the genome.
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1,8-Octanediol, also known as octamethylene glycol, is a diol with the molecular formula HO(CH)OH. 1,8-Octanediol is a white solid. It is produced by hydrogenation of esters of suberic acid. 1,8-Octanediol is used as a monomer in the synthesis of some polymers such as polyesters and polyurethanes.
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Polyglycolic acid is a thermoplastic polymer and an aliphatic polyester. PGA is often used in medical applications such as PGA sutures for its biodegradability. The ester linkage in the backbone of polyglycolic acid gives it hydrolytic instability. Thus polyglycolic acid can degrade into its nontoxic monomer, glycolic acid, through hydrolysis.
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At higher temperatures, the Al2Cl6 dimers dissociate into trigonal planar AlCl3, which is structurally analogous to BF3. The melt conducts electricity poorly, unlike more-ionic halides such as sodium chloride. 500px Aluminium chloride monomer belongs to the point group D3h in its monomeric form and D2h in its dimeric form.
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This colorless liquid has a strong and unpleasant odor. At room temperature, this cyclic diene dimerizes over the course of hours to give dicyclopentadiene via a Diels–Alder reaction. This dimer can be restored by heating to give the monomer. The compound is mainly used for the production of cyclopentene and its derivatives.
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There are two types, human (hMICL) and murine (mMICL). Human MICL is expressed as a monomer primarily on myeloid cells, including granulocytes, monocytes, macrophages and dendritic cells. Murine MICL is expressed as dimer on granulocytes, monocytes but also on B lymfocytes and can be also found on NK cells surface in bone marrow.
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The monomer DADMAC is formed by reacting two equivalents of allyl chloride with dimethylamine. PolyDADMAC is then synthesized by radical polymerization of DADMAC with an organic peroxide used as a catalyst. Two polymeric structures are possible when polymerizing DADMAC: N-substituted piperidine structure or N-substituted pyrrolidine structure. The pyrrolidine structure is favored.
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This non-traditional secretion requires a functional glycan binding site. Galectin 1 contains a single carbohydrate recognition domain through which it can bind glycans both as a monomer and as a homodimer. Dimers are non-covalently bound and will spontaneously disassociate in low concentration. Galectin 1 does not bind glycans when oxidized.
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DAPDC is a PLP-dependent enzyme belonging to the alanine racemase family. This enzyme is generally dimeric with each monomer containing two domains. The first domain is the N-terminal α/β-barrel that binds the PLP to the active site lysine residue. The second domain is the C-terminal β-sandwich.
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3D cartoon representation of the crystal structure of MenB. Each monomer is colored differently.MenB is composed of two hexamers in an asymmetric unit, these hexamers are each composed of two trimers in an eclipsed arrangement. Each sub unit of the hexamers has three C terminal alpha helices, and a N terminal spiral core.
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6FDA is used as monomer for the synthesis of fluorinated polyimides. These are prepared by the polymerisation of 6FDA with an aromatic diamine such as 3,5-diaminobenzoic acid or 4,4'-diaminodiphenyl sulfide. "Synthesis and characterization of a novel carboxyl group containing (co)polyimide with sulfur in the polymer backbone". Beilstein J. Org. Chem.
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1-Vinylimidazole is a water-soluble basic monomer that forms quaternizable homopolymers by free-radical polymerization with a variety of vinyl and acrylic monomers. The products are functional copolymers, which are used as oil field chemicals and as cosmetic auxiliaries. 1-Vinylimidazole acts as a reactive diluent in UV lacquers, inks, and adhesives.
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Porosity Sealing or Resin Impregnation is similar to potting, but doesn't use a shell or a mold. Parts are submerged in a polymerizable monomer or solvent- based low viscosity plastic solution. The pressure above the fluid is lowered to a full vacuum. After the vacuum is released, the fluid flows into the part.
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Omega-amidase has two independent monomers that have structure organizations similar to other nitrilase enzymes found in bacteria. Each monomer has a four layered alpha/beta/beta/alpha conformation. The enzyme is asymmetrical and contains a carbon-nitrogen hydrolase fold. Theoretical active site based on the proximity of residues of the catalytic triad.
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On the other hand, many natural Ets1-responsive GGAA/T elements differ from this consensus sequence. The later suggests that several other transcription factors may facilitate Ets1 binding to unfavorable DNA sequences. ChIP-Seq studies have shown that Ets1 can bind both AGGAAG and CGGAAG motifs. Ets1 binds to DNA as a monomer.
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According to the lab experiments, the sugar battery reaches an electron-transmission efficiency of almost 24 electrons per monomer glucose, which is the basic unit of organic fuels. In comparison, the oxidation reaction in the prototyped enzymatic fuel cells could only generate 2 electrons per glucose unit, resulting in low energy density.
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OcDH is a monomer with a molecular weight of 38kD made of two functionally distinct subunits. The first, Domain I, is composed of 199 amino acids and contains a Rossmann fold. Domain II is composed of 204 amino acids and is connected to the Rossmann fold of Domain I via its N-terminus.
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Simple addition occurs if not conjugated. Other techniques include synthesizing the resin with hydroxyl functional oligomers e.g. containing ethylene glycol then adding specific acid or hydroxyl containing substances towards the end of the reaction. Another technique is making an acrylic functional alkyd with an acrylic monomer blend rich in carboxylic acid groups.
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Idemitsu Petrochemical runs two petrochemical plants in Chiba and Tokuyama. It produces a variety of basic chemicals supplied to chemical industries, in Japan and abroad. In Europe it markets through Idemitsu Chemicals Europe PLC. Basic chemicals produced includes olefins such as ethylene and propylene, and aromatics like benzene, para-xylene and styrene monomer.
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Al-Soufi W, Piñeiro L, Novo M. A model for monomer and micellar concentrations in surfactant solutions: Application to conductivity, NMR, diffusion, and surface tension data. J.Colloid Interface Sci. 2012;370:102-10,DOI: 10.1016/j.jcis.2011.12.037Lucas Piñeiro, Sonia Freire, Jorge Bordello, Mercedes Novo, and Wajih Al-Soufi, Dye Exchange in Micellar Solutions.
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Once bound by ParR at both ends, monomer units continue to attach to the ends of the ParM and the resulting reaction pushes R1 plasmids to opposite ends of the cell. ParMs from different bacterial plasmids can form astonishingly diverse helical structures comprising two or four strands to maintain faithful plasmid inheritance.
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Polyesters are also used in anchor bolt adhesives though epoxy based materials are also used. Many companies have and continue to introduce styrene free systems mainly due to odor issues. Most polyester resins are viscous, pale coloured liquids consisting of a solution of a polyester in a monomer which is usually styrene..
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In 1993, M. Reza Ghadiri reported a nanotubular supramolecular polymer where a b-sheet-forming macrocyclic peptide monomer assembled together via multiple hydrogen bonding between adjacent macrocycles. In 1994, Anselm. C. Griffin showed an amorphous supramolecular material using a single hydrogen bond between a homotropic molecules having carboxylic acid and pyridine termini.
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During the setting process, the liquid monomer polymerizes into the polymer, thereby hardening into a solid. Single- monomer resins may be used in the process, which form homopolymers (polymers containing only one type of polymer). In such uses, the "curing agent" mixed with the resin contains what is loosely referred to as a "catalyst," but which is more technically an initial source of free radicals (such as MEKP) to act as an initiator in a free-radical chemical chain reaction polymerization. Alternately, resin casting may be accomplished with a resin plus a nearly equal amount of a "hardener" liquid (as in many epoxy resin or polyester resin systems), which functionally contains a second polymer, for use in forming a final product plastic which is a copolymer.
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ADA exists in both small form (as a monomer) and large form (as a dimer-complex). In the monomer form, the enzyme is a polypeptide chain, folded into eight strands of parallel α/β barrels, which surround a central deep pocket that is the active site. In addition to the eight central β-barrels and eight peripheral α-helices, ADA also contains five additional helices: residues 19-76 fold into three helices, located between β1 and α1 folds; and two antiparallel carboxy-terminal helices are located across the amino-terminal of the β-barrel. The ADA active site contains a zinc ion, which is located in the deepest recess of the active site and coordinated by five atoms from His15, His17, His214, Asp295, and the substrate.
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When one enantiomer of a properly designed chiral initiator is used for the polymerization, only the monomer with the preferred enantiomeric form polymerizes, resulting in 100% enantiomeric separation of the racemic monomer. These achievements challenged the notion that supramolecular polymerization always follows a step-growth mechanism and revealed the potential of supramolecular polymerization as a tool for precision macromolecular synthesis. In 2017, Aida reported a conceptually new, "thermally bisignate", supramolecular polymerization, where supramolecular polymers are designed in such a way that they form upon heating as well as cooling but disappear at temperatures in between. This work challenged the preconception that supramolecular polymers are more stable at lower temperatures, while they readily dissociate upon heating, unveiling new insights into the dynamic nature of supramolecular polymers.
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The graft copolymer consists of a main polymer chain or backbone (A) covalently bonded to one or more side chains (B) Graft copolymers are a special type of branched copolymer in which the side chains are structurally distinct from the main chain. Typically the main chain is formed from one type of monomer (A) and branches are formed from another monomer (B), or else the side-chains have constitutional or configurational features that differ from those in the main chain. The individual chains of a graft copolymer may be homopolymers or copolymers. Note that different copolymer sequencing is sufficient to define a structural difference, thus an A-B diblock copolymer with A-B alternating copolymer side chains is properly called a graft copolymer.
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Cyclopentadiene is a highly reactive diene in the Diels–Alder reaction because minimal distortion of the diene is required to achieve the envelope geometry of the transition state compared to other dienes. Famously, cyclopentadiene dimerizes. The conversion occurs in hours at room temperature, but the monomer can be stored for days at −20 °C.
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With bulky alky groups, Ti(OiPr)4 in contrast exist as a monomer with a tetrahedral environment around the Ti center. This lower degree of coordination to the metal center is attributed to the steric bulk of the iPr groups versus the n-alkyl groups, this serves to prevent bridging interactions between the metal centers.
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P22TSP is a homotrimeric structural protein consisting of 666 amino acids. It is noncovalently bound to the neck of the viral capsid. It has been crystallized in space group P213 and has one monomer in the asymmetric unit. The secondary structure of P22TSP is dominated by a parallel Beta helix comprising 13 complete turns.
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Nav1.6 is encoded by the SCN8A gene which contains 27 exons and measures 170 kb. The voltage gated sodium channel is composed of 1980 residues. Like other sodium channels, Nav1.6 is a monomer composed of four homologous domains (I-IV) and 25 transmembrane segments. SCN8A encodes S3-S4 transmembrane segments which form an intracellular loop.
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It is commercially available as a solution in mixed hexanes, usually at a concentration of about 2 M for laboratory use or 33% for industrial use. As for BuLi, the structure and formula for HxLi are often depicted as a monomer. Like all organolithium compounds, it exists as clusters in solution and as a solid..
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One of the remarkable features of living anionic polymerization is the absence of a formal termination step. In the absence of impurities, the carbanion would remains active, awaiting the addition of new monomer. Termination can occur through unintentional quenching by impurities, often present in trace amounts. Typical impurities include oxygen, carbon dioxide, or water.
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Together with cresols and cresylic acid, xylenols are an important class of phenolics with great industrial importance. They are used in the manufacture of antioxidants. Xylenol orange is a redox indicator built on a xylenol skeleton. 2,6-Xylenol is a monomer for poly(p-phenylene oxide) (PEO) engineering resins through carbon-oxygen oxidative coupling.
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Figure 1 This ribbon representation of the RT active domain (i.e. the p66 monomer) illustrates its hand-like structure, showing fingers (blue), palm (pink) and thumb (green). The active site (red atoms), where DNA is elongated, is in the palm region. Also shown is an NNRTI drug (yellow) in the pocket where it binds.
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In the research laboratory, 1-methylimidazole and related derivatives have been used as mimic aspects of diverse imidazole-based biomolecules. 1-Methylimidazole is also the precursor for the synthesis of the methylimidazole monomer of pyrrole- imidazole polyamides. These polymers can selectively bind specific sequences of double-stranded DNA by intercalating in a sequence dependent manner.
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ADMET copolymerization with Ru catalyst Acyclic diene metathesis (ADMET) is similar to ROMP in that subsequent hydrogenation is required. ADMET requires a certain type of diene in order for the polymerization to occur. Ruthenium complexes can once again be used for ADMET polymerization. In this case, an α,ω-diene monomer with functionality is required.
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Mannose, packaged as the nutritional supplement "d-mannose", is a sugar monomer of the aldohexose series of carbohydrates. It is a C-2 epimer of glucose. Mannose is important in human metabolism, especially in the glycosylation of certain proteins. Several congenital disorders of glycosylation are associated with mutations in enzymes involved in mannose metabolism.
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C1QBP is 282 amino acid in length and has three homologous subunit with its N-terminal 73 amino acid residues cleaved off to produce mature C1QBP. C1QBP appears as a monomer around 33 kDa on SDS-PAGE gel under both reducing and nonreducing condition but migrates as a trimer on size- exclusion chromatography (gel filtration).
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It was first reported by Rizzardo et al. in 1998. RAFT is one of the most versatile methods of controlled radical polymerization because it is tolerant of a very wide range of functionality in the monomer and solvent, including aqueous solutions. RAFT polymerization has also been effectively carried out over a wide temperature range.
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The cyclic orthoester 2,2-diethoxytetrahydrofuran is a reactive bifunctional monomer which forms biodegradable polyorthoesters of the type POE-I by transesterification with α, ω-diols. :Synthese des Polyorthoester-Typs POE-I Polyorthoesters are used as embedding media for pharmaceuticals in depot drug dosage forms for controlled drug release by surface erosion under physiological conditions.
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RDL allows for the controlled synthesis of ELP gene oligomers, in which single gene segments are sequentially added. However, the restriction endonucleases used are limited to those that do not cut within the ELP monomer gene itself, as this would lead to loss of crucial nucleotides and a potential frameshift mutation in the protein.
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The dynamic instability of ParM and eukaryotic microtubules is believed to be an example of convergent evolution. L ParM spontaneously forms short polymer segments when it is present in the cytoplasm. These segments serve to very efficiently "search" for the R1 plasmids, and also maintains a favorable concentration of ParM monomer units for polymerization.
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Expanding monomers are monomers which increase in volume (expand) during polymerization. They can be added to monomer formulations to counteract the usual volume shrinking (during polymerization) to manufacture products with higher quality and durability. Volume Shrinkage is in first line for the unmeltable thermosets a problem, since those are of fixed shape after polymerization completed.
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2,2,4,4-Tetramethyl-1,3-cyclobutanediol (CBDO) is an aliphatic diol. This diol is produced as a mixture of cis- and trans-isomers, depending on the relative stereochemistry of the hydroxyl groups. It is used as a monomer for the synthesis of polymeric materials. CBDO is currently being researched as an alternative to bisphenol A (BPA).
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The word polymer derives its meaning from this, which means "many mers." A repeat unit (or mer), is not to be confused with the term monomer, which refers to the small molecule from which a polymer is synthesized.Callister, William D. (2007). Materials science and engineering : an introduction (7th ed.) New York : John Wiley & Sons.
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As of late 2007, 7 structures have been solved for this class of enzymes, with PDB accession codes , , , , , , and . The enzyme from Bacillus is a monomer consisting of two domains: an alpha helical N-terminal domain, and a C-terminal domain composed of beta sheets. The active site is a deep cleft located between these two domains.
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Scn crystal structures containing heavy metals (thorium, plutonium, americium, curium, and californium) have been obtained. Scn has been found as a monomer, homo-dimer, or trimer in human plasma. The siderocalin fold is exceptionally stable. The calyx is structurally stable and rigid, and conformational change does not typically occur upon a change in pH, ionic strength, or ligand binding.
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Conjugated polymers have many practical applications, and are used in devices such as photovoltaic cells, organic light-emitting diodes, field-effect transistors, and chemical sensors. Goroff et al. prepared ordered poly(diiododiacetylene) (PIDA) via prearrangement of monomer (2) with a halogen bond scaffolding. PIDA is an excellent precursor to other conjugated polymers, as Iodine can be easily transformed.
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PVDF, Polyvinylidene fluoride, is a fairly non-reactive, thermoplastic fluoropolymer with excellent chemical and thermal resistance for plastic pipework uses. PVDF resin is produced through polymerization of the vinylidene fluoride monomer. The PVDF resin is then used to make PVDF pipe as well as many other products. Industries and applications select PVDF pipe due to its inert, durable qualities.
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Although simple alkyllithium species are often represented as monomer RLi, they exist as aggregates (oligomers) or polymers. The degree of aggregation depends on the organic substituent and the presence of other ligands. These structures have been elucidated by a variety of methods, notably 6Li, 7Li, and 13C NMR spectroscopy and X-ray diffraction analysis. Computational chemistry supports these assignments.
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Skeletal structure of methyl methacrylate, the constituent monomer of PMMA Pieces of perspex, the windscreen of a German plane shot down during World War II PMMA is a strong, tough, and lightweight material. It has a density of 1.17–1.20 g/cm3, which is less than half that of glass.Polymethylmethacrylate (PMMA, Acrylic) . Makeitfrom.com. Retrieved 2015-03-23.
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EGDMA can be used in free radical copolymer crosslinking reactions. When used with methyl methacrylate, it leads to gel point at relatively low concentrations because of the nearly equivalent reactivities of all the double bonds involved. It is used as a monomer to prepare Hydroxyapatite/Poly methyl methacrylate composites. EGDMA can be used in free radical copolymer crosslinking reactions.
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VP1 is capable of self-assembly into virus-like particles even in the absence of other viral components. This process requires bound calcium ions and the resulting particles are stabilized by, but do not require, inter-pentamer disulfide bonds. The structure of an individual pentamer of the murine polyomavirus VP1 protein. Each monomer is colored differently.
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The conformationally flexible C-terminal arms are shown here in conformations compatible with binding to neighboring molecules. Superposed is a fragment of the polyomavirus VP2 protein (white), which binds to a pentamer oriented toward the central cavity. VP1 is from ; VP2 is from . The VP1 protein monomer is primarily composed of beta sheets folded into a jelly roll fold.
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The VIR-576 is a peptide. Consequently, it is a molecule formed by a sequence of amino-acids united by peptide bonds. If we compare both primary structures, it can be seen that the VIR-576 has 2 subunits. Each subunit, monomer is a variant form, a mutant of the VIRIP, differing from four amino acids.
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The DERA monomer contains a TIM α/β barrel fold, consistent with other Class I aldolases. The structure of DERAs across many organisms: DERAs from Escherichia coli and Aeropyrum pernix shares 37.7% sequence identity with DERA from Thermus thermophilus HB8. The reaction mechanism is also conserved between DERAs. In solution, DERAs are found in homodimers or homotetramers.
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The structure of disulfur dioxide, S2O2 A space-filling model of the disulfur dioxide molecule SO converts to disulfur dioxide (S2O2). Disulfur dioxide is a planar molecule with C2v symmetry. The S−O bond length is 145.8 pm, shorter than in the monomer, and the S−S bond length is 202.45 pm. The O−S−S angle is 112.7°.
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Alpha(α)-hemolysin of Staphylococcus aureus: macromolecular structure of the transmembrane pore. Secreted by Staphylococcus aureus, this toxin causes cell death by binding with the outer membrane, with subsequent oligomerization of the toxin monomer and water-filled channels. These are responsible for osmotic phenomena, cell depolarization, and loss of vital molecules (v.gr. ATP), leading to its demise.
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While washing the polymer plates after they have been exposed with ultra-violet light with water and brushes, monomers will enter the sewer system, eventually adding to the plastic content of the oceans. Current water purification installations are not able to remove monomer molecules from sewer water. Some monomers, such as styrene, are toxic or carcinogenic.
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Hydridoiron, also systematically named ferrane(1), is a related compound with the chemical formula FeH (also written [FeH]). It is also unstable at ambient temperature with the additional propensity to autopolymerize, and so cannot be concentrated. Hydridoiron is the simplest molecular iron hydride. In addition, it may be considered to be the iron(I) hydride monomer.
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Acrylonitrile is commonly employed as a comonomer with styrene, e.g. acrylonitrile, styrene and acrylate plastics. Labeling of items of clothing with acrylic (see acrylic fiber) means the polymer consists of at least 85% acrylonitrile as monomer. A typical comonomer is vinyl acetate, which can be solution-spun readily to obtain fibers that soften enough to allow penetration by dyes.
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State of myosin VI from PDB 2V26 before the power stroke Myosin VI is an unconventional myosin motor, which is primarily processive as a dimer, but also acts as a nonprocessive monomer. It walks along actin filaments, travelling towards the pointed end (- end) of the filaments. Myosin VI is thought to transport endocytic vesicles into the cell.
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The sequences of 4-hydroxy-tetrahydrodipicolinate synthase from different sources are well-conserved. The structure takes the form of a homotetramer, in which 2 monomers are related by an approximate 2-fold symmetry. Each monomer comprises 2 domains: an 8-fold alpha-/beta- barrel, and a C-terminal alpha-helical domain. The fold resembles that of N-acetylneuraminate lyase.
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1972, 10 (11), 3295–3310. doi: 10.1002/pol.1972.170101116Nakahara, K.; Iwasa, S.; Satoh, M.; Morioka, Y.; Iriyama, J.; Suguro, M.; Hasegawa, E. Chemical Physics Letters 2002, 359 (5–6), 351–354. doi: 10.1016/S0009-2614(02)00705-4 Similar synthetic approaches have been proposed using 4-methacryloyloxy-N- hydroxy-2,2,6,6-tetramethylpiperidine as a monomer rather than 2,2,6,6- tetramethylpiperidine methacrylate.
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Hybrid filler contains particles of various sizes with filler load of 75-85% by weight. It was designed to get the benefits of both macrofilled and microfilled fillers. Resins with hybrid filler have reduced thermal expansion and higher mechanical strength. However, it has higher polymerisation shrinkage due to a larger volume of diluent monomer which controls viscosity of resin.
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The solution to this problem is to seal the internal voids prior to plating. As explained above, the porosity is saturated with monomer and is then rinsed completely clear of the surface. The resin cures to a durable polymer. Thus, the exposed surface metal is free to be plated while the interior spaces are sealed dry.
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Recovery of unreacted monomers is close to 100%. After monomer recovery, latex is sent through a series of filters to remove unwanted solids and then sent to the blending tanks where it is stabilized with an antioxidant. The yielded polymer latex is coagulated using calcium nitrate, aluminium sulfate, and other coagulating agents in an aluminium tank.
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Chloroprene is the common name for 2-chlorobuta-1,3-diene (IUPAC name) with the chemical formula CH2=CCl−CH=CH2. Chloroprene is a colorless volatile liquid, almost exclusively used as a monomer for the production of the polymer polychloroprene, a type of synthetic rubber. Polychloroprene is better known as Neoprene, the trade name given by DuPont.
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R496 is located on this small helix (see Mutations). The core structure of the hexamer is a stacked dimer of trimers. Glu-BDs of the monomers are mainly responsible in the buildup of the core. The relative position of the monomers is such that the rotation about the pivot helix in each monomer is not restricted.
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The basic cartoon structures of dimeric, tandem and chimeric galectins. Dimeric galectins consist of two of the same subunit that have associated with one another. Tandem galectins have two distinct CRDs linked via a linker peptide domain. Chimera galectins, which consist of only galectin-3 in vertebrates, can exist as a monomer or in a multivalent form.
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In solution the dimeric form is present; the ratio of dimerisation is strongly dependent on the polarity of the solvent. Polar and protic solvents interact with the hydrogen bonds and more monomer is formed. Hydrophobic effects in non-polar solvents lead to a predominance of the dimer. The ratio of the tautomeric forms is also dependent on the solvent.
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Lehigh has commercialized a proprietary cryogenic turbo mill technology that transforms end-of-life tires and post-industrial rubber materials into micronized rubber powders. Lehigh produces MRP from vulcanized elastomeric material, most often end-of-life tire material. However, it can also be produced from post-industrial nitrile rubber, ethylene propylene diene monomer (EPDM), butyl, and natural rubber compounds.
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An oligosaccharide is an oligomer of monosaccharides (simple sugars). An oligonucleotide is a short single-stranded fragment of nucleic acid such as DNA or RNA, or similar fragments of analogs of nucleic acids such as peptide nucleic acid or Morpholinos. A pentamer unit of the major capsid protein VP1. Each monomer is in a different color.
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Ribbon diagram of a monomer of human MAO-A, with FAD and clorgiline bound, oriented as if attached to the outer membrane of a mitochondrion. From . MAOIs act by inhibiting the activity of monoamine oxidase, thus preventing the breakdown of monoamine neurotransmitters and thereby increasing their availability. There are two isoforms of monoamine oxidase, MAO-A and MAO-B.
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Bulk slurry (or bulk): Uses liquid propylene instead of liquid inert hydrocarbon diluent. The polymer does not dissolve into a diluent, but rather rides on the liquid propylene. The formed polymer is withdrawn and any unreacted monomer is flashed off. Gas phase: Uses gaseous propylene in contact with the solid catalyst, resulting in a fluidized-bed medium.
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Polypropylene (PP), also known as polypropene, is a thermoplastic polymer used in a wide variety of applications. It is produced via chain-growth polymerization from the monomer propylene. Polypropylene belongs to the group of polyolefins and is partially crystalline and non-polar. Its properties are similar to polyethylene, but it is slightly harder and more heat resistant.
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This image shows that DAHP synthase consists of two tightly bound dimers. Each of the monomer chains is colored differently. Below the first image to the right is an image of DAHP synthase that also shows quaternary structure, however this image is in a cartoon view. This view also shows each of the four monomers colored differently.
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Cortactin is a thin, elongated monomer that consists of an amino-terminal acidic (NTA) region; 37-residue-long segments that are highly conserved among cortactin proteins of all species and repeated up to 6.5 times in tandem (“cortactin repeats”); a proline-rich region; and an SH3 domain. This basic structure is highly conserved among all species that express cortactin.
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Trichohyalin belongs to the S100-fused protein family. It is a monomer, containing 1943 amino acids, and has elongated (>200 nm) single-stranded alpha-helical conformation based on its unusually high content of charged residues. Molecular mass of the human trichohyalin is 253925 Da. The protein includes nine domains. Domain 1 contains two EF-hand calcium-binding domains.
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This N-terminal domain of approximately 100 amino acids is the most highly conserved region in the HSF protein family and consists of a helix-turn-helix loop. The DBD of each HSF1 monomer recognizes the sequence nGAAn on target DNA. Repeated sequences of the nGAAn pentamer constitute heat shock elements (HSEs) for active HSF1 trimers to bind.
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The protein encoded by this gene is a ubiquitous actin monomer- binding protein belonging to the profilin family. It is thought to regulate actin polymerization in response to extracellular signals. Deletion of this gene is associated with Miller-Dieker syndrome. Mutations in this gene may be a rare cause of amyotrophic lateral sclerosis, also called Lou Gehrig's disease.
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Unsaturated polyesters are thermosetting resins. They are generally copolymers prepared by polymerizing one or more diol with saturated and unsaturated dicarboxylic acids (maleic acid, fumaric acid...) or their anhydrides. The double bond of unsaturated polyesters reacts with a vinyl monomer, usually styrene, resulting in a 3-D cross-linked structure. This structure acts as a thermoset.
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This swimming board is made of polystyrene, an example of a polymer. One important property of carbon is that it readily forms chains, or networks, that are linked by carbon-carbon (carbon-to-carbon) bonds. The linking process is called polymerization, while the chains, or networks, are called polymers. The source compound is called a monomer.
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Therefore, chitin may be described as cellulose with one hydroxyl group on each monomer replaced with an acetyl amine group. This allows for increased hydrogen bonding between adjacent polymers, giving the chitin-polymer matrix increased strength. A cicada emerges from its chitinous larval exoskeleton. In its pure, unmodified form, chitin is translucent, pliable, resilient, and quite tough.
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Molecular structure of an hypothetical xylooligosaccharide, where n is a variable number of xylose units. Xylooligosaccharides (XOS) are polymers of the sugar xylose. They are produced from the xylan fraction in plant fiber. Their C5 (where C is a quantity of carbon atoms in each monomer) structure is fundamentally different from other prebiotics, which are based upon C6 sugars.
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Profilin-2 is a protein that in humans is encoded by the PFN2 gene. The protein encoded by this gene is a ubiquitous actin monomer-binding protein belonging to the profilin family. It is thought to regulate actin polymerization in response to extracellular signals. There are two alternatively spliced transcript variants encoding different isoforms described for this gene.
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Polystyrene is commonly used in containers for food and drinks. The styrene monomer (from which polystyrene is made) is a cancer suspect agent. Styrene is "generally found in such low levels in consumer products that risks aren't substantial". Polystyrene which is used for food contact may not contain more than 1% (0.5% for fatty foods) of styrene by weight.
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Shikimate dehydrogenase also has an NADPH binding site that contains a Rossmann fold. This binding site normally contains a glycine P-loop. The domains of the monomer show a fair amount of flexibility suggesting that the enzyme can open in close to bind with the substrate 3-Dehydroshikimate. Hydrophobic interactions occur between the domains and the NADPH binding site.
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Dipropylene glycol finds many uses as a plasticizer, an intermediate in industrial chemical reactions, as a polymerization initiator or monomer, and as a solvent. Its low toxicity and solvent properties make it an ideal additive for perfumes and skin and hair care products. It is also a common ingredient in commercial fog fluid, used in entertainment industry fog machines.
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TetR as a homodimer: Each monomer is shown in purple or salmon. The helix- turn-helix motif is shown in deep red. Tet Repressor proteins (otherwise known as TetR) are proteins playing an important role in conferring antibiotic resistance to large categories of bacterial species. Tetracycline (tc) is a broad family of antibiotics to which bacteria have evolved resistance.
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The two main approaches into this class of polymers are the macromonomer route and the attach-to route. In the former, a monomer which already carries the dendron of final size is polymerized. In the latter the dendrons are constructed generation by generation directly on an already existing polymer. Figure 4 illustrates the difference for a simple case.
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Eintrag zu functionality, f of a monomer. From the average functionality of the used monomers the reaching of the gel point can be calculated as a function of reaction progress.Koltzenburg: Polymere: Synthese, Eigenschaften und Anwendungen, S. 187 (). This reference is being translated to English as "Polymer Chemistry" by the same authors, to appear in September 2017.
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Due to its aforementioned biocompatibility, Poly(methyl methacrylate) is a commonly used material in modern dentistry, particularly in the fabrication of dental prosthetics, artificial teeth, and orthodontic appliances. ; Acrylic prosthetic construction: Pre-polymerized, powdered PMMA spheres are mixed with a Methyl Methacrylate liquid monomer, Benzoyl Peroxide (initiator), and NN-Dimethyl-P-Toluidine (accelerator), and placed under heat and pressure to produce a hardened polymerized PMMA structure. Through the use of injection molding techniques, wax based designs with artificial teeth set in predetermined positions built on gypsum stone models of patients' mouths can be converted into functional prosthetics used to replace missing dentition. PMMA polymer and methyl methacrylate monomer mix is then injected into a flask containing a gypsum mold of the previously designed prosthesis, and placed under heat to initiate polymerization process.
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Studies provide evidence through monolayer measurements, condensing properties, and nearly identical gel to liquid-crystalline phase transition temperatures (Tm) to the host membranes that the presence of these bonds do not play a major role or interfere in the recognition or packing formation of the modeled membranes in the presence of ethanol. The disulfide bonds, diacylglycerol bonds, and similar sterol framework are only present to mimic the physical properties of DSPC, DPPC, and cholesterol as well as aid in the monomer exchanging processes to form exchangeable dimers. The exchangeable lipids undergo a monomer interchanging process through the disulfide bridges in which they either mix ideally, homogenously, or heterogeneously. Their interactions are measured by the equilibrium constant (K) which will be described in further detail under the significance of results section.
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Fischer and co-workers also studied the chemistry of iridocene, the third transition series analogue of rhodocene and cobaltocene, finding the chemistry of rhodocene and iridocene are generally similar. The synthesis of numerous iridocenium salts including the tribromide and hexafluorophosphate have been described. Just as with rhodocene, iridocene dimerises at room temperature but a monomer form can be detected at low temperatures and in gas phase and IR, NMR, and ESR measurements indicate a chemical equilibrium is present and confirm the sandwich structure of the iridocene monomer. The complex [(η5-C5H5)Ir(η4-C5H6)], the analogue of rhodocene derivative reported by Fischer, has also been studied and demonstrates properties consistent with a greater degree of π-backbonding in iridium(I) systems than is found in the analogous cobalt(I) or rhodium(I) cases.
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Figure 1: Example of a (a) diblock copolymer, (b) gradient copolymer and (c) random copolymer Copolymers are polymers that are synthesized with more than one kind of repeat unit (or monomer). Gradient copolymers exhibit a gradual change in monomer composition from predominantly one species to predominantly the other, unlike with block copolymers, which have an abrupt change in composition, and random copolymers, which have no continuous change in composition (see Figure 1). In the gradient copolymer, as a result of the gradual compositional change along the length of the polymer chain less intrachain and interchain repulsion are observed. The development of controlled radical polymerization as a synthetic methodology in the 1990s allowed for increased study of the concepts and properties of gradient copolymers because the synthesis of this group of novel polymers was now straightforward.
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In the late 1970s, tooth adhesion phosphate monomer: 2-methacryloyloxethyl phenyl hydrogen phosphate (Phenyl-P) was developed for tooth substance saving restoration technique.J. Yamauchi, N. Nakabayashi, E. Masuhara, “Adhesive Agents for Hard Tissue Containing Phosphoric Acid Monomers”, ACS Polymer Preprints, Vol. 2 (1), 594-595 (1979). 4-Methacryloyloxyethyl trimellitic acid anhydride (4-META) that adhere to not only tooth structures but also dental alloys, was developed almost at the same time.M. Takeyama, S. Kashibuchi, N. Nakabayashi, E. Masuhara, ”Studies on Dental Self-Curing Resins (17). Adhesion of PMMA with Bovine Enamel or Dental Alloys”, Journal of the Japan Society for Dental Apparatus and Materials, 19（47）179-185 (1978)． In order to create adhesive monomers having higher performance, investigation and optimization of adhesive monomer molecular structure was carried out.
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3,9-Divinyl-2,4,8,10-tetraoxaspiro[5.5]undecane (DVTOSU) is a bicyclic organic molecule having a central quaternary carbon atom (a spiro atom) with which two alicyclic rings are linked, each comprising five atoms. DVTOSU is a diallyl acetal and the precursor for the isomeric ketene acetal monomer 3,9-diethylidene-2,4,8,10-tetraoxaspiro[5.5]undecane (DETOSU) which is a building block for polyorthoesters.
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The ball-and-stick model of diisobutylaluminium hydride, showing aluminium as pink, carbon as black, and hydrogen as white. Organoaluminium chemistry is the study of compounds containing bonds between carbon and aluminium bond. It is one of the major themes within organometallic chemistry. Illustrative organoaluminium compounds are the dimer trimethylaluminium, the monomer triisobutylaluminium, and the titanium-aluminium compound called Tebbe's reagent.
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Varying the composition of monomers and cross-linking can add or change the functionality of a polymer that can alter the results obtained from DMA. An example of such changes can be seen by blending ethylene propylene diene monomer (EPDM) with styrene-butadiene rubber (SBR) and different cross-linking or curing systems. Nair et al. abbreviate blends as E0S, E20S, etc.
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SPI resin ID code 2 High-density polyethylene (HDPE) or polyethylene high- density (PEHD) is a thermoplastic polymer produced from the monomer ethylene. It is sometimes called "alkathene" or "polythene" when used for HDPE pipes.Pipe materials. level.org.nz With a high strength-to-density ratio, HDPE is used in the production of plastic bottles, corrosion-resistant piping, geomembranes and plastic lumber.
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Poly(methacrylic acid) (PMAA) is a polymer made from methacrylic acid (preferred IUPAC name, 2-methylprop-2-enoic acid), which is a carboxylic acid. It is often available as its sodium salt, poly(methacrylic acid) sodium salt. The monomer is a viscous liquid with a pungent odour. The first polymeric form of methacrylic acid was described in 1880 by Engelhorn and Fittig.
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In statistical mechanics, a degree of freedom is a single scalar number describing the microstate of a system. The specification of all microstates of a system is a point in the system's phase space. In the 3D ideal chain model in chemistry, two angles are necessary to describe the orientation of each monomer. It is often useful to specify quadratic degrees of freedom.
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Nuclear actin exists mainly as a monomer, but can also form dynamic oligomers and short polymers. Nuclear actin organization varies in different cell types. For example, in Xenopus oocytes (with higher nuclear actin level in comparison to somatic cells) actin forms filaments, which stabilize nucleus architecture. These filaments can be observed under the microscope thanks to fluorophore-conjugated phalloidin staining.
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A monomer of the double jelly roll major capsid protein P2 from bacteriophage PM2. The two distinct jelly roll domains are shown in red and blue, with the remaining protein sequence in orange. In contrast to single jelly roll capsids, double jelly rolls are oriented with the "vertical" axis perpendicular to the capsid surface, which is at the bottom in this image. From .
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Twinfilin-2 is a protein that in humans is encoded by the TWF2 gene. The protein encoded by this gene was identified by its interaction with the catalytic domain of protein kinase C-zeta. The encoded protein contains an actin-binding site and an ATP-binding site. It is most closely related to twinfilin (PTK9), a conserved actin monomer-binding protein.
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Molecular structure of Kevlar: bold represents a monomer unit, dashed lines indicate hydrogen bonds. When Kevlar is spun, the resulting fiber has a tensile strength of about 3,620 MPa, and a relative density of 1.44. The polymer owes its high strength to the many inter-chain bonds. These inter-molecular hydrogen bonds form between the carbonyl groups and NH centers.
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Polyquaternium-7 is used as modifier, for example in shampoo, hair conditioner, hair spray, mousse, soap, gel, styling agent, shaving product, deodorant and antiperspirant. The DADMAC monomer is highly hydrophilic. Absorption of moisture from the air lends "conditioning" properties to the products that contain the copolymer such as shampoos, hair and skin conditioners and other personal care products including some bar soaps.
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This particular protein is an octamer made up of 8 identical subunits. Each monomer consists of a central domain and a C-terminal alpha helix. The central domain consists of a five-stranded parallel beta sheet flanked by three alpha helices one side of the sheet and two alpha helices on the other, forming a three-layer (alpha beta alpha) sandwich.
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Synthetic fibers are created by a process known as polymerization, which involves combining monomers to make a long chain or polymer. The word polymer comes from a Greek prefix "poly" which means "many" and suffix "mer" which means "single units". (Note: each single unit of a polymer is called a monomer). There are two types of polymerization: linear polymerization and cross-linked polymerization.
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The monomer contains 432 amino acids, and is divisible (can be cleaved) into three chains, such as jellein-1, jellein-2, and jellein-4. The monomers in the ologomer are held together by apimisin using noncovalent bonds. The oligomer is resistant to high temperature. MRJP2, MRJP3, MRJP4 and MRJP5 are smaller and their size range between 49 and 80 kDa.
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N-Vinylcarbazole is an organic compound used as a monomer in the production of poly(vinylcarbazole), a conductive polymer, in which conductivity is photon- dependent. The compound is used in the photoreceptors of photocopiers. Upon exposure to γ-irradiation, N-vinylcarbazole undergoes solid-state polymerisation. It is produced by the vinylation of carbazole with acetylene in the presence of base.
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Factor for Inversion Stimulation (Fis) is a sequence specific DNA binding protein that binds to specific DNA sequences containing a 15-bp symmetric motif. Like IHF, Fis induces DNA bending at cognate sites. The ability to bend DNA is apparent in the structure of Fis homodimer. A Fis homodimer possesses two helix-turn- helix (HTH) motifs, one from each monomer.
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Thioredoxin reductases (TR, TrxR) () are the only known enzymes to reduce thioredoxin (Trx). Two classes of thioredoxin reductase have been identified: one class in bacteria and some eukaryotes and one in animals. Both classes are flavoproteins which function as homodimers. Each monomer contains a FAD prosthetic group, a NADPH binding domain, and an active site containing a redox-active disulfide bond.
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Isobutyl cyanoacrylate is an isomer of butyl cyanoacrylate. It is used in medical procedures either to close incisions and lacerations without the use of sutures, or as an adjunct to strengthen the suturing. This use is possible because it is a bactericidal liquid monomer which, in the presence of small amounts of moisture, rapidly polymerizes to form a strong adhesive.
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Heparin mimicking polymers can be characterized by various techniques. For example, both proton nuclear magnetic resonance (H1NMR) and FTIR spectroscopy can aid in the identification of functional groups. However H1NMR depicts a better image of the chemical structure of the monomer. Contact angle measurements can help determine the hydrophobicity or hydrophilicity of the polymer, this extremely useful for creating water-soluble biomaterials.
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It is shown to be sufficient and necessary for apical RNA transport in microinjection assays and transgenic reporters. Indeed, deletion of WLE3 in an otherwise full-length wg 3'UTR completely abolishes apical localization. However, a minimal WLE3 monomer by itself shows weak activity on its own. The incomplete activity of a single WLE3 element indicates a requirement for additional elements or sequences.
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She has also invented liquid crystalline temperature recorders, where the liquid crystal contains a reactive monomer and an initiator that can crosslink. Working with Andre Geim, Gleeson produced the first graphene liquid crystal device. The devices contained transparent graphene electrodes, and had an exceptionally high contrast ratio. Gleeson went on to use graphene in the switchable liquid crystalline contact lenses.
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Actin exists in two states in the axonal and dendritic processes: globular or G-actin and filament/filamentous or F-actin. G-actin are the monomer building blocks that assemble via weak noncovalent interactions to form F-actin. F-actin is a two-stranded asymmetrical helical polymer. The asymmetrical quality of F-actin allows for different binding specificities at each end.
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Homopolysaccharides are polysaccharides composed of a single type of sugar monomer. For example, cellulose is an unbranched homopolysaccharide made up of glucose monomers connected via beta-glycosidic linkages; glycogen is a branched form, where the glucose monomers are joined by alpha-glycosidic linkages. Depending upon the molecules attached that are of the following types 1\. Glucan - A polysaccharide of glucose 2\.
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The photopolymers always include a prepolymer (the monomer) and, considering the final application, a photoinitiator, as a catalyzer for the polymerization reaction. In addition, we can find such polymerization inhibitors (useful to stabilize resins both reducing the obtained voxel), solvents (which may simplify casting procedures), thickens (so called "fillers") and other additives (as pigments and so on) which aim to functionalize the photopolymer.
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All members of the Vps10p protein family are multiligand receptors. They can take part in cellular trafficking and signaling through ligand binding in response to cellular conditions. Examples of ligands are neurotrophic factors, amyloid precursor protein (APP), lipoproteins, and cytokines. In addition to depending on the cellular context, the affinity for specific ligands can also be modulated by the monomer/dimer ratio.
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Some models use fixed bonds, defined at the start of the simulation, while others have dynamic bonding. More recent efforts strive for robust, transferable models with generic functional forms: spherical harmonics, Gaussian kernels, and neural networks. In addition, MD can be used to simulate groupings of atoms within generic particles, called coarse-grained modeling, e.g. creating one particle per monomer within a polymer.
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Instead of working as a complex, the methyltransferase and endonuclease are encoded as two separate proteins and act independently (there is no specificity protein). Both proteins recognize the same recognition site, and therefore compete for activity. The methyltransferase acts as a monomer, methylating the duplex one strand at a time. The endonuclease acts as a homodimer, which facilitates the cleavage of both strands.
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The copper binding domain of azurin rendered in PyMol, with four of the five copper-binding ligands labeled. The distance (in angstroms) from the copper atom to each individual ligand has been recorded. Azurin is a tetrameric protein. Each monomer weighs approximately 14kDa and is composed of 128 amino acids forming eight beta-strands arranged in a beta-barrel formation.
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The biosynthesis of hibarimicinone was initially hypothesized to be produced from a polyketide synthase. Through 13C-labelling and blocked mutants of the TP-A0121 strain, Oki et al. demonstrated that hibarimicinone is produced by an oxidative coupling of two tetracyclic polyketides, which undergo an oxidative cyclization to generate the ether ring. The hibarimicinone monomer is formed initially by a Type II polyketide synthase.
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According to the Eleventh Development Plan (2019-2023): > The lignite reserves in our country will be evaluated and feasibility > studies will be carried out in order to establish gasification reactors that > enable the production of coal-sourced chemicals (ammonia, methanol, monomer, > synthetic natural gas, hydrogen, synthetic liquid diesel fuel, etc). R & D > projects related to clean coal technologies will be supported.
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The first few amino acids were discovered in the early 19th century. In 1806, French chemists Louis-Nicolas Vauquelin and Pierre Jean Robiquet isolated a compound in asparagus that was subsequently named asparagine, the first amino acid to be discovered. Cystine was discovered in 1810, although its monomer, cysteine, remained undiscovered until 1884. Glycine and leucine were discovered in 1820.
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IgA prevents entry and colonization of pathogenic bacteria in the gut. It can be found as a monomer, dimer, or tetramer, allowing it to bind multiple antigens simultaneously. IgA coats pathogenic bacterial and viral surfaces (immune exclusion), preventing colonization by blocking their attachment to mucosal cells, and can also neutralize PAMPs. IgA promotes the development of TH17 and FOXP3+ regulatory T cells.
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Chemically, polydioxanone is a polymer of multiple repeating ether-ester units. It is obtained by ring-opening polymerization of the monomer p-dioxanone. The process requires heat and an organometallic catalyst like zirconium acetylacetone or zinc L-lactate. It is characterized by a glass transition temperature in the range of −10 and 0 °C and a crystallinity of about 55%.
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The succinate-binding site and ubiquinone-binding site are connected by a chain of redox centers including FAD and the iron- sulfur clusters. This chain extends over 40 Å through the enzyme monomer. All edge-to-edge distances between the centers are less than the suggested 14 Å limit for physiological electron transfer. This electron transfer is demonstrated in image 8.
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Oligosaccharides are needed to maintain esterase activity in the F and R domains. If any of the domains lack an oligosaccharide chain, cell surface expression will be affected. It was found that HE monomer have acetylesterase activity because they possessed full-enzyme activity despite lack of an oligosaccharide chain. Oligosaccharide chains are important for intracellular transport, but not for fusion activity.
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It contained no glass, and the plates were aligned horizontally to the surface of the tooth. These deeper layers were tougher, resembling dentine. The tooth was then cooked at 1,600 degrees to compact and harden the material — a process known as sintering. The last step involved filling remaining pores with a synthetic monomer used in dentistry, which polymerizes after treatment.
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Polyvinyl chloride is produced by polymerization of the vinyl chloride monomer (VCM), as shown. The polymerisation of vinyl chloride About 80% of production involves suspension polymerization. Emulsion polymerization accounts for about 12%, and bulk polymerization accounts for 8%. Suspension polymerization affords particles with average diameters of 100–180 μm, whereas emulsion polymerization gives much smaller particles of average size around 0.2 μm.
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Acetone peroxide (also called APEX) is an organic peroxide and a primary high explosive. It is produced by the reaction of acetone and hydrogen peroxide to yield a mixture of linear monomer and cyclic dimer, trimer, and tetramer forms. The trimer is known as triacetone triperoxide (TATP) or tri-cyclic acetone peroxide (TCAP). The dimer is known as diacetone diperoxide (DADP).
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Residues in hydrophobic pocket are highlighted in yellow. The base of the pocket is formed by the residue in green (a phenylalanine). A 90 degree rotated monomer structure is shown in Inset 1 to highlight the hydrophobic pocket. A top view of the active site is shown in Inset 2 along with the aspartate mediated trinuclear Mg2+ (silver spheres) catalytic center.
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The monomer, vinyl acetate, was first produced on an industrial scale by the addition of acetic acid to acetylene with a mercury(I) saltRutherford John Gettens and George Leslie Stout, Painting Materials: A Short Encyclopaedia (Princeton, New Jersey: D. Van Nostrand, 1942),page 74. but it is now primarily made by palladium catalyzed oxidative addition of acetic acid to ethylene.
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Copolymers are polymers consisting of multiple different monomer species, and can be arranged in various orders, three of which are seen in the figure below. Various common forms of copolymers. Here, the two different colored circles represent two different monomers. While there exist others (alternating copolymers, graft copolymers, and stereoblock copolymers), these three are more common in the scientific literature.
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The domains are connected by loops. The monomers connect to each other via interactions between the barrel of one monomer and the sheet of the other. Binding between monomers is relatively weak, and ODC interconverts rapidly between monomeric and dimeric forms in the cell. The pyridoxal phosphate cofactor binds lysine 69 at the C-terminus end of the barrel domain.
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Copolymer via radical polymerization Radical polymerization occurs with an olefin and a vinyl monomer. Since olefins are not very reactive, harsh conditions must be met in order for the polymerization to occur. Ethylene and ethyl acrylate can react together to perform free radical polymerization. In this process, boron trifluoride can be used as the protected group for the ethyl acrylate.
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When polyacrylamide gel is denatured after electrophoresis, it provides information on the sample composition of the RNA species. Hydration of acrylonitrile results in formation of acrylamide molecules () by nitrile hydratase. Acrylamide monomer is in a powder state before addition of water. Acrylamide is toxic to the human nervous system, therefore all safety measures must be followed when working with it.
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Ring-opening metathesis polymerization (ROMP) produces unsaturated polymers from cycloalkenes or bicycloalkenes. It requires organometallic catalysts. The mechanism for ROMP follows similar pathways as olefin metathesis. The initiation process involves the coordination of the cycloalkene monomer to the metal alkylidene complex, followed by a [2+2] type cycloaddition to form the metallacyclobutane intermediate that cycloreverts to form a new alkylidene species.
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Chain growth polymerization (American spelling) or chain-growth polymerisation (English spelling) is a polymerization technique where unsaturated monomer molecules add onto the active site on a growing polymer chain one at a time.Introduction to Polymers 1987 R.J. Young Chapman & Hall There are a limited number of these active sites at any moment during the polymerization which gives this method its key characteristics.
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Compared to step-growth polymerization, living chain- growth polymerization shows low PDI, predictable molecular mass and controllable conformation. Some researchers are working on the transformation of two polymerization methods. Generally, polycondensation proceeds in a step- growth polymerization mode. Substituent effect, catalyst transfer and biphasic system could be used for inhibiting the activity of monomer, and further prevent monomers from reacting with each other.
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Therefore, the particular area can be polished with acrylic bur. Leaching of residual monomer methylmethacrylate from inadequately cured denture acrylic resin material can cause mucosal irritation and hence oral ulceration as well. Advise the person to use warm salt water mouth rinses and a betamethasone rinse can heal ulcer. Review of persisting oral ulcerations for more than 3 weeks is recommended.
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Methacrylates are common monomers in polymer plastics, forming the acrylate polymers. Methacrylates easily form polymers because the double bonds are very reactive. They are used as the monomer resin in some windscreen repair kits, dental materials and as bone cement for fixing prosthetic devices in orthopedic surgery. The term (meth)acrylate is frequently used as a generic for acrylate and methacrylate.
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Newer findings suggest the lack of psychedelic action arises from the phenomenon of biased agonism. Stimulation of the 5-HT2A protomer within the 5-HT2A-mGlu2 receptor complex evokes psychedelic effects, while these effects do not occur during sole stimulation of monomeric 5-HT2A receptors. Accordingly, different G-proteins are involved. Lisuride behaves as an agonist at the 5-HT2AR monomer.
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Vinyl ester resins made by addition reactions between an epoxy resin with acrylic acid derivatives, when diluted/dissolved in a vinyl functional monomer such as styrene, polymerise. The resulting thermosets are notable for their high adhesion, heat resistance and corrosion resistance. They are stronger than polyesters and more resistant to impact than epoxies.F.A. Cassis and R.C. Talbot in Handbook of Composites, ed.
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Nitrosobenzene and other nitrosoarenes typically participate in a monomer-dimer equilibrium. The dimers are often favored in the solid state, whereas the deeply colored monomers are favored in dilute solution or at higher temperatures. The dimers can be formulated as Ar(O−)N+=N+(O−)Ar. They exist as cis- and trans-isomers due to the presence of the N–N double bond.
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The dimers are sometimes called azobenzenedioxides. The cis-trans isomerization occurs via the intermediacy of the monomer. In the case of nitrosobenzene itself, the metastable monomeric form could be prepared by sublimation onto a cold finger. The monomeric material is selectively sublimed due to its lower molecular weight and is collected on a cold finger as lustrous, dark green crystals.
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Unusually for a metalloprotein, this enzyme shows activity with several different metals. Glyoxalase I is also unusual in that it is stereospecific in the second half of its mechanism, but not in the first half. Structurally, the enzyme is a domain-swapped dimer in many species, although the two subunits have merged into a monomer in yeast, through gene duplication.
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The tendency of TaF5 to form clusters in the solid state indicates the Lewis acidity of the monomer. Indeed, TaF5 reacts with fluoride sources to give the ions , , and . With neutral Lewis bases, such as diethyl ether TaF5 forms adducts. is used in combination with HF as a catalyst for the alkylation of alkanes and alkenes and for the protonation of aromatic compounds.
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2DPs as two dimensional sheet macromolecules have a crystal lattice, that is they consist of monomer units that repeat in two dimensions. Therefore, a clear diffraction pattern from their crystal lattice should be observed as a proof of crystallinity. The internal periodicity is supported by electron microscopy imaging, electron diffraction and Raman- spectroscopic analysis. 2DPs should in principle also be obtainable by, e.g.
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Methods for estimating secondary structure in polymers, proteins and polypeptides in particular, often require that the measured molar ellipticity spectrum be converted to a normalized value, specifically a value independent of the polymer length. Mean residue ellipticity is used for this purpose; it is simply the measured molar ellipticity of the molecule divided by the number of monomer units (residues) in the molecule.
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Polysilicon hydrides are polymers containing only silicon and hydrogen. They have the formula (SiH_{n})_{x} where 0.2 ≤ n ≤ 2.5 and x is the number of monomer units. The polysilicon hydrides are generally colorless or pale- yellow/ocher powders that are easily hydrolyzed and ignite readily in air. The surfaces of silicon prepared by MOCVD using silane (SiH4) consist of a polysilicon hydride.
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As of late 2007, six structures have been solved for this class of enzymes, with PDB accession codes , , , , , and . CKα-2 originating from C. elegans, is a dimeric enzyme with each monomer being composed of two domains. The active site is located between the two domains (see figure below). Its overall structure is similar to members of the eukaryotic protein kinase family.
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The kinetic chain is not terminated if the new radical can add monomer. However the degree of polymerization is reduced without affecting the rate of polymerization (which depends on kinetic chain length), since two (or more) macromolecules are formed instead of one.Harry R. Allcock, Frederick W. Lampe and James E. Mark Contemporary Polymer Chemistry (3rd ed., Pearson Prentice-Hall 2003) p.
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Approximately, as the termination decreases by a factor of 4, the overall rate of reaction will double. The decrease of termination reactions also allows radical chains to add monomer for longer time periods, raising the mass-average molecular mass dramatically. However, the number-average molecular mass only increases slightly, leading to broadening of the molecular mass distribution (high dispersity, very polydispersed product).
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Glutathione S-transferases form homodimers, but in eukaryotes can also form heterodimers of the A1 and A2 or YC1 and YC2 subunits. The homodimeric enzymes display a conserved structural fold. Each monomer is composed of a distinct N-terminal sub-domain, which adopts the thioredoxin fold, and a C-terminal all-helical sub-domain. This entry is the C-terminal domain.
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Impurities and the presence of MDP dimer affected not only hybridization, but also reduced the formation of MDP_Ca salts and nano-layering. MDP in a high purity grade is essential to achieve durable bonding.K. Yoshihara, N. Nagaoka, T. Okihara, M. Kuroboshi, S. Hayakawa, Y. Maruo, G. Nishigawa, J. De Munck, Y. Yoshida, B. Van Meerbeek, "Functional monomer impurity affects adhesive performance." Dental Materials.
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FKM (fluorocarbon) is a family of fluoroelastomer materials defined by the ASTM International standard D1418. It is equivalent to FPM by ISO/DIN 1629 standard. All FKMs contain vinylidene fluoride as a monomer. Originally developed by DuPont (Viton®), FKMs are today also produced by Daikin Chemical (Dai-El), 3M's Dyneon (Dyneon Fluoroelastomers), Solvay Specialty Polymers (Tecnoflon), HaloPolymer (Elaftor) and several Chinese manufacturers.
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It has a low melting and boiling point. It is mainly produced and consumed in the production of aluminium metal, but large amounts are also used in other areas of the chemical industry. The compound is often cited as a Lewis acid. It is an example of an inorganic compound that reversibly changes from a polymer to a monomer at mild temperature.
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This enables side-on addition of an ethylene unit and a polymer chain can grow by migratory insertion. Chromium compounds also catalyse the trimerization of ethylene to produce the monomer 1-hexene.John T. Dixon, Mike J. Green, Fiona M. Hess, David H. Morgan “Advances in selective ethylene trimerisation – a critical overview” Journal of Organometallic Chemistry 2004, Volume 689, Pages 3641-3668.
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The ParM monomer unit is non-functional before binding a GTP nucleotide. Once the GTP has been bound it can attach to the end of a growing filament. At some point after attachment the ParM hydrolyzes GTP which becomes GDP and remains in the ParM subunit as long as the polymer strand remains intact. ParM forms a left-handed helix structure.
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In solution or crystal, Der f 1 is a monomer. Der f 1 has been shown to express polymorphism, with at least two haplotypes observed in different regions. Der f 1 can be inhibited by chestnut cystatin, which is thought to stem from the presence of the amino acid Gln152 (instead of Der p 1's Arg151) near the enzyme's active site.
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In addition to the inconveniently low-boiling monomer (b.p. 21 °C), acetaldehyde is available as the trimer paraldehyde (a sedative and anticonvulsant) and tetramer metaldehyde (a slug and snail poison). In general, higher aliphatic aldehydes will accumulate a substantial amount of oligomer (mostly trimer) upon long-term storage and must be freshly distilled when a reaction calls for the monomeric starting material.
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A well known derivative is titanium isopropoxide, which is a monomer. Organic amines react with TiCl4 to give complexes containing amido (R2N−-containing) and imido (RN2−-containing) complexes. With ammonia, titanium nitride is formed. An illustrative reaction is the synthesis of tetrakis(dimethylamido)titanium Ti(NMe2)4, a yellow, benzene-soluble liquid: This molecule is tetrahedral, with planar nitrogen centers.
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Molecular modelling has become a convenient choice in MIP design and analysis, allowing rapid selection of monomers and optimisation of polymer composition, with a range of different techniques being applied. The application of molecular modelling in this capacity is commonly attributed to Sergey A. Piletsky, who developed a method of automated screening of a large database of monomers against a given target or template with a molecular mechanics approach. In recent years technological advances have permitted more efficient analysis of monomer-template interactions by quantum mechanical molecular modelling, providing more precise calculations of binding energies. Molecular dynamics has also been applied for more detailed analysis of systems before polymerisation, and of the resulting polymer, which by including more system components (initiator, cross-linkers, solvents) provide greater accuracy in predicting successful MIP synthesis than monomer-template interactions alone.
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EM reconstruction of Perfringolysin O pre-pore(A) and pore(B) structure. The binding of CDC to the target membrane is required for oligmerization. The oligomerization of the CDC requires the conversion of alpha-helical regions to amphipathic beta-strands that is initiated by protein-lipid interactions or protein-protein interactions. The water-soluble form of the toxins is prevented from oligomerizing by having the access of one edge of a core β-sheet in the monomer blocked. To be specific, β5, a short polypeptide loop, hydrogen-bonds to β4, preventing β4 interaction with β1 on the adjacent monomer. The binding of D4 to the membrane surface triggers a conformational change in domain 3, which rotates β5 away from β4, exposing β4 allowing it to interact with the β1 strand of another PFO molecule, initiating oligomerization.
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The position of the main RAFT equilibrium (Figure 5) is affected by the relative stabilities of the RAFT adduct radical (Pn-S-C•(Z)-S-Pm) and its fragmentation products, namely S=C(Z)S-Pn and polymeric radical (Pm•). If formation of the RAFT adduct radical is sufficiently thermodynamically favorable, the concentration of active species, Pm•, will be reduced to the extent that a reduction in the rate of conversion of monomer into polymer is also observed, as compared to an equivalent polymerization without RAFT agent. Such a polymerization, is referred to as a rate-retarded RAFT polymerization. The rate of a RAFT polymerization, that is, the rate of conversion of monomer into polymer, mainly depends on the rate of the Propagation reaction (Figure 5) because the rate of initiation and termination are much higher than the rate of propagation.
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In group 12 zinc hydride is a common chemical reagent but cadmium hydride and mercury hydride are very unstable and esoteric. In group 13 boron hydrides exist as a highly reactive monomer BH3, as an adduct for example ammonia borane or as dimeric diborane and as a whole group of BH cluster compounds. Alane (AlH3) is a polymer. Gallium exists as the dimer digallane.
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The monomer repeat unit of unsubstituted polythiophene. Polythiophenes demonstrate interesting optical properties resulting from their conjugated backbone, as demonstrated by the fluorescence of a substituted polythiophene solution under UV irradiation. Polythiophenes (PTs) are polymerized thiophenes, a sulfur heterocycle. They are white solids with the formula (C4H2S)n for the parent PT.Strictly speaking, "polythiophene" is a misnomer, since the polymer consists of thienylene (2,5-C4H2S) repeat units.
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Higher molecular weights were reported when dry air was bubbled through the reaction mixture during polymerization. Exhaustive Soxhlet extraction after polymerization with polar solvents was found to effectively fractionate the polymer and remove residual catalyst before NMR spectroscopy. Using a lower ratio of catalyst to monomer (2:1, rather than 4:1) may increase the regioregularity of poly(3-dodecylthiophene)s. Andreani et al.
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In the first stage of the reaction the pernigraniline PS salt oxidation state is formed. In the second stage pernigraniline is reduced to the emeraldine salt as aniline monomer gets oxidized to the radical cation. In the third stage this radical cation couples with ES salt. This process can be followed by light scattering analysis which allows the determination of the absolute molar mass.
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Six dimers related by C6 symmetry compose the enzymatically active dodecamer (approximately 106 Da). Each monomer of L30a OrnDC can be described in terms of five sequential folding domains. The amino-terminal domain, residues 1 to 107, consists of a five-stranded beta-sheet termed the "wing" domain. Two wing domains of each dimer project inward towards the centre of the dodecamer and contribute to dodecamer stabilisation.
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The full assembled capsid structure of the satellite tobacco mosaic virus, with the monomer shown above at the bottom of the highlighted pentamer. The remainder of the protein chains are shown in purple and the RNA in the interior of the capsid is shown in brown. The axis of the jelly roll in this single jelly roll capsid is parallel to the capsid surface. From .
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The monomer p80 is found in all the compartments of the neuron, which means its function cannot be solely to target katanin. The p80 katanin has multiple domains with different functions. One domain targets the centrosome, another augments microtubule severing by the p60 katanin, and the last suppresses microtubule severing. The abundance of katanin in the neurons show they can move along the axon.
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The first commercial application of photoionization detection was in 1973 as a hand-held instrument for the purpose of detecting leaks of VOCs, specifically vinyl chloride monomer (VCM), at a chemical manufacturing facility. The photoionization detector was applied to gas chromatography (GC) three years later, in 1976.Driscoll, J.N., and J.B. Clarici: Ein neuer Photoionisationsdetektor für die Gas-Chromatographie. Chromatographia, 9:567-570 (1976).
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Carlson, Dana P. (1991-08-06) "Base resistant fluoroelastomers with improved processibility and curability". . Therefore, the iodine is easily abstracted in the presence of free radicals. Upon encountering an iodoperfluoroalkane, a growing poly(fluoroolefin) chain will abstract the iodine and terminate, leaving the now-created perfluoroalkyl radical to add further monomer. But the iodine-terminated poly(fluoroolefin) itself acts as a chain transfer agent.
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Regulatory elements of CCDC113 include transcription factors ATF2, FOXD1, LCR-F1, C/EBPalpha, Max, AREB6, CBF-A, CBF(2), c-Myc, and HIF. Interacting proteins found using two-hybrid screening techniques include GIT1; a G protein-coupled receptor kinase interacting ArfGAP, the cytoplasmic protein HAP1; Huntingtin-associated protein 1, IMMT, an inner mitochondrial membrane protein, and PFN2; Profilin 2- ubiquitous actin monomer binding protein.
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Two colorizations of the dimeric substructure of the enzyme. Left side distinguishes the enzyme's secondary structures and right side distinguishes the two monomers. Derived from Oxalyl-CoA decarboxylase is tetrameric, and each monomer consists of three α/β-type domains. The thiamine diphosphate-binding site rests on the subunit-subunit interface between two of the domains, which is commonly seen in its class of enzymes.
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Among a number of various molecules, Receptor Tyrosine Kinases (RTKs ) play a critical role in transducing signals through a range of signaling pathways. All RTKs consists of an extracellular ligand binding region, a single transmembrane helix and a cytoplasmic region (the tyrosine kinase domain). Prior to ligand stimulation most RTKs present as a monomer on the surface of cells. Ligand binding to the extracellular domain induces dimerization.
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Soy protein/poly(acrylic acid) superabsorbent polymers with good mechanical strength have been prepared. Polyacrylate/polyacrylamide copolymers were originally designed for use in conditions with high electrolyte/mineral content and a need for long term stability including numerous wet/dry cycles. Uses include agricultural and horticultural. With the added strength of the acrylamide monomer, used as medical spill control, wire and cable water blocking.
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He found two proteins as potential markers for freshness of royal jelly protein and named them royal jelly proteins (RJP-1 and RJP-2). RJP-1 was a 57-kDa monomer which is a subunit of a larger complex (oligomer). In 2011, Kamakura claimed that RJP-1 is the main protein for controlling larval development that distinguishes the queen from workers. He gave a new name royalactin.
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Tenglong Cave () is a cave located from Lichuan City, Hubei, China. It is believed to be the longest monomer karst cave system in the world. The cave entrance is and wide, leading to of passageways.. An underground network of streams runs for whilst the cave is the source of the Qingjiang River. Year round temperatures underground remain in the 16-18 degrees Celsius range.
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Carlson, Dana P. (1991-08-06) "Base resistant fluoroelastomers with improved processibility and curability". . Therefore, the iodine is easily abstracted in the presence of free radicals. Upon encountering an iodoperfluoroalkane, a growing poly(fluoroolefin) chain will abstract the iodine and terminate, leaving the now-created perfluoroalkyl radical to add further monomer. But the iodine-terminated poly(fluoroolefin) itself acts as a chain transfer agent.
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Product of the reductive coupling of styrene with lithium, 1,4-dilithio-1,4-diphenylbutane. In the original work, Szwarc studied the analogous disodium compound. As early as 1936, Karl Ziegler proposed that anionic polymerization of styrene and butadiene by consecutive addition of monomer to an alkyl lithium initiator occurred without chain transfer or termination. Twenty years later, living polymerization was demonstrated by Szwarc and coworkers.
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Crystal structure analysis of the first phosphatase domain of PTPkappa demonstrates that it shares many conformational features with PTPmu, including an unhindered open conformation for the catalytically important WPD loop, and a phosphate binding loop for the active-site cysteine (Cys1083). PTPkappa exists as a monomer in solution, with the caveat that dimers of PTPkappa are observed depending on the nature of the buffer used.
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If the MTOC does not replicate, the spindle cannot form, and mitosis ceases prematurely. γ-tubulin is a protein located at the centrosome that nucleates the microtubules by interacting with the tubulin monomer subunit in the microtubule at the minus end. Organization of the microtubules at the MTOC, or centrosome in this case, is determined by the polarity of the microtubules defined by y-tubulin.
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Allyl glycidyl ether is an organic compound used in adhesives and sealants and as a monomer for polymerization reactions. It is formally the condensation product of allyl alcohol and glycidol via an ether linkage. Because it contains both an alkene and an epoxide group, either group can be reacted selectively to yield a product where the other functional group remains intact for future reactions.
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Darjeeling black tea infusion: Finer black tea has a more orange tone than red as a result of higher theaflavins content. Catechin monomer structures are metabolized into dimers theaflavins and oligomers thearubigins with increasing degrees of oxidation of tea leaves. Theaflavins contribute to the bitterness and astringency of black tea. The mean amount of theaflavins in a cup of black tea (200 ml) is 12.18 mg.
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Not only are there fewer nitroxide groups present, but also side reactions between non-oxidized groups and oxammonium cations diminishes the redox reversibility of the compound. The difficulties of free-radical polymerization of PTMA could be avoided if the oxidation step were not necessary. However, because nitroxide radicals would react with any carbon radicals formed during polymerization, use of a monomer with a nitroxide radical isn’t practical.
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One of the more recent techniques identified to synthesis PTMA is a type of free radical polymerization known as reversibly addition-fragmentation chain transfer (RAFT) mediated polymerization.Rostro, L.; Baradwaj, A. G.; Boudouris, B. W. ACS Appl. Mater. Interfaces 2013, 5 (20), 9896–9901. doi: 10.1021/am403223s RAFT mediated polymerization of TEMPO RAFT-mediated polymerization of PTMA utilizes the same starting monomer as free-radical polymerization.
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Both of these chemokines share many genetic and functional similarities; however XCL2 has only been known to be observed in humans and not in mice. XCL1 induces it chemotactic function by binding to a chemokine receptor called XCR1. XCL1 is expressed on macrophages, fibroblasts, and specific lymphocytes. LTN, is found in two states: a monomer at 10 °C, LTN10, and a dimer at 40 °C, LTN40.
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In-situ polymerization can be used for polymers that are not solvent or heat compatible. In this method, the nanotubes are mixed with the monomer, which is then reacted to form the polymer matrix. This method can lead to especially good load transfer if monomers are also attached to the carbon nanotube surface. Graphene Like carbon nanotubes, pristine graphene also possesses exceptionally good mechanical properties.
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Itaconic anhydride is the cyclic anhydride of itaconic acid (a unsaturated, dicarboxylic acid) and is obtained by the pyrolysis of citric acid. The itaconic anhydride (as a derivative of the so-called biobased platform chemical itaconic acid) is propagated as a versatile monomer and building block because of its easy accessibility from inexpensive renewable raw materials; however, it has not yet fulfilled those expectations.
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These morphologies can be stabilized by sufficient interfacial adhesion or lowered interfacial tension between the two phases. A common technique involves functionalizing one monomer. For example, Nylon-rubber bands are polymerized with functionalized rubber to produce graft or block copolymers. The added structures make it no longer favorable to coalesce and/or increase the steric hindrance in the interfacial area where phase separation would occur.
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Hexafluoropropylene oxide (HFPO) is an intermediate used in industrial organofluorine chemistry; specifically it is a monomer for fluoropolymers. This colourless gas is the epoxide of hexafluoropropylene, that is fluorinated analog of propylene oxide, HFPO is produced by DuPont and 3M and as a precursor to the lubricant Krytox and related materials. It is generated by oxidation of perfluoropropylene, e.g. with oxygen as well as other oxidants.
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Like polyphosphates of polyphenols, PEP can be prepared from the monomer (in this case estradiol) and phosphoryl chloride. The latter reacts with both the phenolic hydroxyl group in position 3 and the aliphatic one in position 17β. The molecular mass of the resulting polymer can be controlled by interrupting the reaction after a given time: the longer the reaction is allowed to continue, the higher the mass.
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TLR5 is expressed on both immune and non-immune cells. TLR5 recognizes bacterial flagellin, a principal component of bacterial flagella and a virulence factor. The activation of this receptor mobilizes the nuclear factor NF-κB and stimulates tumor necrosis factor-alpha production. TLR5 recognizes flagellin, which is the protein monomer that makes up the filament of bacterial flagella, found on nearly all motile bacteria.
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Medicinal Natural Products. John Wiley and Sons, LTD Multiple aldol additions occur to form four six-membered cyclization and aromization (2). The CLF/KS subunit is cleaved off by a thioesterase and modified by numerous steps (four oxidations, two NADPH dependent reductions, two methylations and decarboxylation) to form the final monomeric unit (3). Two monomer units undergo oxidative coupling to form the atropisomeric axis (4).
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P-glycoprotein is a well- studied protein associated with multi-drug resistance. It belongs to the human ABCB (MDR/TAP) family and is also known as ABCB1 or MDR1 Pgp. MDR1 consists of a functional monomer with two transmembrane domains (TMD) and two nucleotide- binding domains (NBD). This protein can transport mainly cationic or electrically neutral substrates as well as a broad spectrum of amphiphilic substrates.
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Poly(4-vinylphenol), also called polyvinylphenol or PVP, is a plastic structurally similar to polystyrene. It is produced from the monomer 4-vinylphenol, which is also referred to as 4-hydroxystyrene. PVP is used in electronics as a dielectric layer in organic transistors in organic TFT LCD displays. Thin films of cross-linked PVP can be used in this application, often in combination with pentacene.
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They often form dimers, unlike their boron analogues, but this tendency diminishes for branched-chain alkyls (e.g. Pri, Bui, Me3CCH2); for example, triisobutylaluminium exists as an equilibrium mixture of the monomer and dimer. These dimers, such as trimethylaluminium (Al2Me6), usually feature tetrahedral Al centers formed by dimerization with some alkyl group bridging between both aluminium atoms. They are hard acids and react readily with ligands, forming adducts.
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Bullcroft Brook rises near Caerau, south of the A4232 road. It is just under 2 miles long, and flows southward to join the Wrinstone Brook at Michaelston-le-Pit. On 19 April 2005 the stream was polluted when a vehicle carrying styrene monomer lost 620 litres of the chemical, which heavy rains carried to Bullcroft Brook. The trout in the river system suffered as a result.
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The peptidase ClpP is highly conserved throughout organisms and is tightly regulated. Without activation, ClpP in normal conditions can degrade short peptides that freely diffuse into its inner degradation chamber. Clp-family proteins are ATP-dependent proteases which play a crucial role in the cell function by degrading misfolded proteins. ClpP is a monomer on its own but oligomerizes into tetradecamers when bound to ATPases.
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Atg8 is a monomer of 117 aminoacids and a molecular weight of 13,6kDa. It consists of a 5-stranded β-sheet, which is enclosed by two α-helices at one side and one α-helix at the other side and exhibits a conserved GABARAP domain. Even though Atg8 does not show a clear sequence homology to ubiquitin, its crystal structure reveals a conserved ubiquitin-like fold.
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An Endoglycosidase is an enzyme that releases oligosaccharides from glycoproteins or glycolipids. It may also cleave polysaccharide chains between residues that are not the terminal residue, although releasing oligosaccharides from conjugated protein and lipid molecules is more common. It breaks the glycosidic bonds between two sugar monomer in the polymer. It is different from exoglycosidase that it does not do so at the terminal residue.
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For example, for the polymerization of ethylene, 93.6 kJ of energy are released per mole of monomer. The manner in which polymerization is conducted is a highly evolved technology. Methods include emulsion polymerization, solution polymerization, suspension polymerization, and precipitation polymerization. Although the polymer dispersity and molecular weight may be improved, these methods may introduce additional processing requirements to isolate the product from a solvent.
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Atomic carbon, systematically named carbon and λ0-methane, also called monocarbon, is colourless gaseous inorganic chemical with the chemical formula C (also written [C]). It is kinetically unstable at ambient temperature and pressure, being removed through autopolymerisation. Atomic carbon is the simplest form of carbon, and is also the progenitor of carbon clusters. In addition, it may be considered to be the graphite monomer.
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We deduce an important fact about the coefficients rk, which we recall given the number of non-attacking placements of k rooks in B: these numbers are unimodal, i.e., they increase to a maximum and then decrease. This follows (by a standard argument) from the theorem of Heilmann and LiebOle J. Heilmann and Elliott H. Lieb, Theory of monomer-dimer systems. Communications in Mathematical Physics, Vol.
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The MICA gene is highly polymorphic in humans with more than 50 defined alleles. It is located on chromosome 6 and the protein is expressed in two isoforms formed by alternative splicing: MICA1 and MICA2 which is lacking exon 3. MICA contains external α1α2α3 domain, transmembrane segment and C-terminal cytoplasmic tail. It binds in a form of monomer to a KLRK1/NKG2D homodimer.
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The Hmd holoenzyme includes the protein homodimer as well as its associated iron-containing co-factor. Several species of methanogens have been characterized that express enzymes in the Hmd hydrogenase family. Between species the enzyme is found with differing numbers of sub-units and some minor amino acid sequence variations. The monomer is approximately 45,000 Da in mass, although this value varies from species to species.
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This allows for easier application of the coating. One dispersion polymerization system being studied is the use of supercritical liquid carbon dioxide (scCO2) as a solvent. Because of its unique solvent properties, supercritical CO2 is an ideal medium for dispersion polymerization for many soluble-monomer with insoluble-polymer systems. For example, polymers can be separated by releasing the high pressure under which the scCO2 is held.
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A general image of a multifunctional branch unit, A_f, reacting with bifunctional monomers with A and B functional groups to form a step-growth polymer. The Flory-Stockmayer Theory predicts the gel point for the system consisting of three types of monomer unitsFlory, P.J.(1941). "Molecular Size Distribution in Three Dimensional Polymers II. Trifunctional Branching Units". J. Am. Chem. Soc. 63, 3091Flory, P.J. (1941).
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To close the mathematical system a further equation, the Stefan condition, is required. This is an energy balance which defines the position of the moving interface. Note that this evolving boundary is an unknown (hyper-)surface; hence, Stefan problems are examples of free boundary problems. Analogous problems occur, for example, in the study of porous media flow, mathematical finance and crystal growth from monomer solutions.
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Polyvinyl Chloride (PVC) membrane roofing is also known as vinyl roofing. Vinyl is derived from two simple ingredients: fossil fuel and salt. Petroleum or natural gas is processed to make ethylene, and salt is subjected to electrolysis to separate out the natural element chlorine. Ethylene and chlorine are combined to produce ethylene dichloride (EDC), which is further processed into a gas called vinyl chloride monomer (VCM).
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Glutamate racemase is a bacterial enzyme that is encoded by the murI gene. This enzyme is most commonly known as being responsible for the synthesis of bacterial cell walls. Through experimentation it was found that this enzyme is able to construct these cell walls by synthesizing D-glutamate from L-glutamate through racemization. D-glutamate is a monomer of the peptidoglycan layer in prokaryotic cell walls.
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It plays an important role in the elongation step of protein synthesis. Unlike most ribosomal proteins, which are basic, the encoded protein is acidic. Its C-terminal end is nearly identical to the C-terminal ends of the ribosomal phosphoproteins P0 and P2. The P1 protein can interact with P0 and P2 to form a pentameric complex consisting of P1 and P2 dimers, and a P0 monomer.
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Like other organic compounds, polystyrene burns to give carbon dioxide and water vapor, in addition to other thermal degradation by-products. Polystyrene, being an aromatic hydrocarbon, typically combusts incompletely as indicated by the sooty flame. The process of depolymerizing polystyrene into its monomer, styrene, is called pyrolysis. This involves using high heat and pressure to break down the chemical bonds between each styrene compound.
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There are covalent bonds formed between boron and nitrogen atoms, yet the layers are held together by weak van der Waals interactions, in which the boron atoms are eclipsed over the nitrogen. Figure 2. Surface-mediated 2D polymerization scheme of the tetrafunctional porphyrin monomer. Two dimensional covalent organic frameworks (COFs) are one type of microporous coordination polymer that can be fabricated in the 2D plane.
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Cytidine monophosphate, also known as 5'-cytidylic acid or simply cytidylate, and abbreviated CMP, is a nucleotide that is used as a monomer in RNA. It is an ester of phosphoric acid with the nucleoside cytidine. CMP consists of the phosphate group, the pentose sugar ribose, and the nucleobase cytosine; hence, a ribonucleoside monophosphate. As a substituent it takes the form of the prefix cytidylyl-.
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This property, together with a higher toughness compared to epoxies, also makes it a valuable material in aerospace applications. For example, the Lynx Mark II spaceplane is primarily made of carbon/cyanate ester. The chemistry of the cure reaction is a trimerization of three CN groups to a triazine ring. When the monomer contains two cyanate groups the resulting structure is a 3D polymer network.
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Guanosine monophosphate (GMP), also known as 5'-guanidylic acid or guanylic acid (conjugate base guanylate), is a nucleotide that is used as a monomer in RNA. It is an ester of phosphoric acid with the nucleoside guanosine. GMP consists of the phosphate group, the pentose sugar ribose, and the nucleobase guanine; hence it is a ribonucleoside monophosphate. Guanosine monophosphate is commercially produced by microbial fermentation.
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The compound is a polymer consisting of distorted octahedral W centres. The monomer is characterized by two short W-O distances, typical for a multiple W-O bond, and two long W-O distances more typical of a single or dative W-O bond.Jarchow, O.; Schröder, F.; Schulz, H. "Kristallstruktur und Polytypie von WO2Cl2" Zeitschrift für anorganische und allgemeine Chemie 1968, vol. 363, p. 345ff.
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The C-terminal domain binds to NADPH. It has a special structure, a Rossmann fold, whereby six-stranded twisted and parallel beta sheet with loops and alpha helices surrounding the core beta sheet. The Structure of Shikimate dehydrogenase is characterized by two domains, two alpha helices and two beta sheets with a large cleft separating the domains of the monomer. The enzyme is symmetrical.
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The American Plastics Council (APC) is a defunct trade association for the U.S. plastics industry. Through a variety of outreach efforts, APC works to promote the benefits of plastics and the plastics industry. APC comprises 22 of the leading resin manufacturers, plus one affiliated trade association representing the vinyl industry. APC's membership represents more than 80 percent of the U.S. monomer and polymer production and distribution capacity.
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The mechanism is now explained further with the help of Figure 5. Initiation: The reaction is started by a free-radical source which may be a decomposing radical initiator such as AIBN. In the example in Figure 5, the initiator decomposes to form two fragments (I•) which react with a single monomer molecule to yield a propagating (i.e. growing) polymeric radical of length 1, denoted P1•.
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This protein is a member of the RUNX family of transcription factors and has a Runt DNA-binding domain. It is essential for osteoblastic differentiation and skeletal morphogenesis. It acts as a scaffold for nucleic acids and regulatory factors involved in skeletal gene expression. The protein can bind DNA both as a monomer or, with more affinity, as a subunit of a heterodimeric complex.
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The activated C=C double bond of vinylsulfonic acid reacts readily with nucleophiles in an addition reaction. 2-Aminoethanesulfonic acid is formed with ammonia and 2-methylaminoethanesulfonic acid with methylamine. Vinylsulfonic acid is the monomer in the preparation of highly acidic or anionic homopolymers and copolymers. These polymers are used in the electronic industry as photoresists, as ion-conductive polymer electrolyte membranes (PEM) for fuel cells.
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Monomers capable of forming single, double, triple or quadruple hydrogen bonding has been utilized for making supramolecular polymers, and increased association of monomers obviously possible when monomers have maximum number of hydrogen bonding donor/acceptor motifs. For instance, ureidopyrimidinone-based monomer with self-complementary quadruple hydrogen bonding termini polymerized in solution, accordingly with the theory of conventional polymers and displayed a distinct viscoelastic nature at ambient temperatures.
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They also tend to hydrate, forming the geminal diol. Formaldehyde is often sold as the aqueous solution, formalin, which is mostly 1,1-methanediol, with a small amount of methanol added as stabilizer. The oligomers/polymers and the hydrates exist in equilibrium with the parent aldehyde, and for some synthetic procedures, they can serve as substitutes for the anhydrous monomer. Aldehydes are readily identified by spectroscopic methods.
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The ingredient or monomer is ethylene (IUPAC name ethene), a gaseous hydrocarbon with the formula C2H4, which can be viewed as a pair of methylene groups (––) connected to each other. Typical specifications are <5 ppm for water, oxygen, and other alkenes. Acceptable contaminants include N2, ethane (common precursor to ethylene), and methane. Ethylene is usually produced from petrochemical sources, but also is generated by dehydration of ethanol.
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The biomembrane is held tightly to the rubber core due to the high negative charge along the double bonds of the rubber polymer backbone. Free monomeric units and conjugated proteins make up the outer layer. The rubber precursor is isopentenyl pyrophosphate (an allylic compound), which elongates by Mg2+-dependent condensation by the action of rubber transferase. The monomer adds to the pyrophosphate end of the growing polymer.
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Benzene and BTX are purchased overseas and is transported to nearby Coode Island where it is unloaded from ships and stored in a similar tank farm before being transported by road to the West Footscray site. The tank farm also contains similar tanks that contain the finished product styrene monomer and various intermediate liquids. See descriptions of these materials in the other sections below.
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Human Serine hydroxymethyltransferase 2 (SHMT2) regulates one-carbon transfer reactions required for amino acid and nucleotide metabolism, and the regulated switch between dimeric and tetrameric forms of SHMT2, which is induced by Pyridoxal phosphate, has recently been shown to be involved in regulation of the BRISC deubiqutylase complex, linking metabolism to inflammation. The SHMT2 dimer, but not the PLP-bound tetramer, is a potent inhibitor of the multimeric BRISC complex, revealing a potential mechanism for SHMT2 regulation of inflammation A single SHMT monomer can be subdivided into three domains: an N-terminus “arm,” a “large” domain, and a “small” domain. The N-terminus arm appears to maintain the tight interaction between two monomers. The arm, consisting of two alpha helices and a beta sheet, wraps around the other monomer when in oligomeric form. The “large” domain contains the PLP binding site, as seen in other PLP-dependent proteins, like aspartate aminotransferase.
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Pentacene.Polymers Oligomers and polymers based on pentacene have been explored both synthetically as well as in device application settings. Polymer light emitting diodes (PLEDs) have been constructed using conjugated copolymers (1a–b) containing fluorene and pentacene. A few other conjugated pentacene polymers (2a–b and 3) have been realized based on Sonogashira and Suzuki coupling reactions of a dibromopentacene monomer. Non-conjugated pentacene- based polymers have been synthesized via esterification of a pentacene diol monomer with bis-acid chlorides to form polymers 4a–b. OLIGOMERS Various synthetic strategies have been employed to form conjugated oligomers of pentacene 5a–c including a one-pot-four-bond forming procedure which provided a solution-processable conjugated pentacene dimer (5c) which exhibited photoconductive gain >10, placing its performance within the same order of magnitude as thermally evaporated films of non-functionalized pentacene which exhibited photoconductive gain >16 using analogous measurement techniques.
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The molecule is chiral and the separate enantiomers have been isolated. Certain barrelenes have been used as a monomer in a ring opening metathesis polymerization :Synthesis of Poly(1,4-naphthylenevinylenes): Metathesis Polymerization of Benzobarrelenes Lin Pu, Michael W. Wagaman, and Robert H. Grubbs Macromolecules; 1996; 29(4) pp 1138 - 1143; (Article) Synthesis of Organic and Water Soluble Poly(1,4-phenylenevinylenes) Containing Carboxyl Groups: Living Ring-Opening Metathesis Polymerization (ROMP) of 2,3-Dicarboxybarrelenes Michael W. Wagaman, and Robert H. Grubbs Macromolecules; 1997; 30(14) pp 3978–3985; (Article) :Benzobarrelene polymerization The catalyst is a Fischer carbene (a molybdenum bis-(hexafluoro-tert-butoxy) carbene catalyst) and the long alkyl chain attached to the monomer is required for solubility. Oxidation of the polymer with DDQ affords the naphthalene pendant of poly(p-phenylene vinylene). Isopentane solutions of barrelene undergo photolytic isomerisation when acetone is added as a photosensitizer to produce semibullvalene.
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Each monomer consists of five alpha helices surrounding five beta sheets. Of these, two antiparallel beta sheets and one alpha helix are located in a subdomain where the N-terminus and C-terminus are in close juxtaposition. The homohexamer exhibits a threefold axis perpendicular to a twofold axis. Within the wide V-groove, there are twelve hydrogen bonds and six salt bridges between the monomers in the presence of phosphate binding.
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As HIV-1 PR can only function as a dimer, the mature protease contains two Asp25 amino acids, one from each monomer, that act in conjunction with each other as the catalytic residues. Additionally, HIV protease has two molecular "flaps" which move a distance of up to 7 Å when the enzyme becomes associated with a substrate. This can be visualized with animations of the flaps opening and closing.
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In polymer chemistry, a comonomer refers to a polymerizable precursor to a copolymer aside from the principal monomer. In some cases, only small amounts of a comonomer are employed, in other cases substantial amounts of comonomers are used. Furthermore, in some cases, the comonomers are statistically incorporated within the polymer chain, whereas in other cases, they aggregate. The distribution of comonomers is referred to as the "blockiness" of a copolymer.
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The thiol-based polymers have disulfide bonds that can be reversibly cross-linked through oxidation and reduction. Under reducing condition, the disulfide (SS) bridges in the polymer breaks and results in monomers, however, under oxidizing condition, the thiols (SH) of each monomer forms the disulfide bond, cross-linking the starting materials to form the polymer. Chujo et al. have shown the thiol-based reversible cross-linked polymer using poly(N-acetylethyleneimine).
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Depiction of crack propagation through microcapsule-imbedded material. Monomer microcapsules are represented by pink circles and catalyst is shown by purple dots. In contrast, in multicapsule systems both the catalyst and the healing agent are encapsulated in different capsules. In a third system, called latent functionality, a healing agent is encapsulated, that can react with the polymerizer component that is present in the matrix in the form of residual reactive functionalities.
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The more open arrangement of the domains displays rotational movement of the two domains around a single hinge region. The structural flexibility has been described as a "butterfly like" cleft opening around the active site. In E. coli, exopolyphosphatase exists as a dimer, with each monomer consisting of four domains. The first two domains consist of three beta-sheets followed by an alpha-beta-alpha-beta-alpha fold.
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Structure of a Fab with light and heavy chains. The antigen-binding fragment (Fab) is a region on an antibody that binds to antigens. It is composed of one constant and one variable domain of each of the heavy and the light chain. The variable domain contains the paratope (the antigen-binding site), comprising a set of complementarity-determining regions, at the amino terminal end of the monomer.
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Other than its direct use as a monomer, glucose can be broken down to synthesize a wide variety of other biomolecules. This is important, as glucose serves both as a primary store of energy and as a source of organic carbon. Glucose can be broken down and converted into lipids. It is also a precursor for the synthesis of other important molecules such as vitamin C (ascorbic acid).
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Murine polyomavirus VP1 in complex with the GT1a glycan. GT1a is shown in yellow and the VP1 monomer with a white surface and a blue protein backbone. A complex network of hydrogen bonds, many water-mediated, is shown at the binding surface by orange lines, with participating protein residues shown as sticks. Mutations of the two residues shown in cyan at the bottom of the figure can significantly affect pathogenicity.
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The chemical investigation on royal jelly started in the 1960s. Jozef Hanes and Jozef Šimuth, of the Slovak Academy of Sciences, were the first to identify major royal jelly protein from the hypopharyngeal glands. In 1992 they isolated the protein as a complex of two molecules. MRJP1 as a single molecule (monomer) was first isolated by Masaki Kamakura and his team at the Toyama Prefectural University in 2001.
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Dihydridochromium, also systematically named chromane(2), is a related compound with the chemical formula (also written ). It is both thermodynamically and kinetically unstable at ambient temperature with the additional propensity to autopolymerise, and so cannot be concentrated. Dihydridochromium is the second simplest molecular chromium hydride (after hydridochromium), and is also the progenitor of clusters with the same stoichiometry. In addition, it may be considered to be the chromium(II) hydride monomer.
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PPO is listed as a morpheein, a protein that can form two or more different homo-oligomers (morpheein forms), but must come apart and change shape to convert between forms. It exists as a monomer, trimer, tetramer, octamer or dodecamer, creating multiple functions. In plants, PPO is a plastidic enzyme with unclear synthesis and function. In functional chloroplasts, it may be involved in oxygen chemistry like mediation of pseudocyclic photophosphorylation.
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The GAPs that act on small GTP-binding proteins of the Ras superfamily have conserved structures and use similar mechanisms, An example of a GTPase is the monomer Ran, which is found in the cytosol as well as the nucleus. Hydrolysis of GTP by Ran is thought to provide the energy needed to transport nuclear proteins into the cell. Ran is turned on and off by GEFs and GAPs, respectively.
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Polyaniline nanofibers can also be synthesized through "rapid mixing" reactions. This method attempts to prevent overgrowth that would compromise the nanofiber nature of the polymer by stopping the polymerization immediately after nanofibers have been formed. This is achieved by the rapid mixing of the monomer, aniline, and an initiator solution. At the start of the reaction, the initiator is consumed rapidly and completely depleted when the nanofibers are formed.
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SPI resin ID code 4 Schematic of LDPE branching structure Low-density polyethylene (LDPE) is a thermoplastic made from the monomer ethylene. It was the first grade of polyethylene, produced in 1933 by Imperial Chemical Industries (ICI) using a high pressure process via free radical polymerization. Its manufacture employs the same method today. The EPA estimates 5.7% of LDPE (recycling number 4) is recycled in the United States.
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1-octene Octene is an alkene with the formula . Several isomers of octene are known, depending on the position and the geometry of the double bond in the carbon chain. The simplest isomer is 1-octene, an alpha-olefin used primarily as a co-monomer in production of polyethylene via the solution polymerization process. Several useful structural isomers of the octenes are obtained by dimerization of isobutene and 1-butene.
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Similar to other caspases, caspase-9 has three domains: N-terminal pro-domain, large subunit, and a small subunit. The N-terminal pro-domain is also called the long pro-domain and this contains the caspase activation domain (CARD) motif. The pro-domain is linked to the catalytic domain by a linker loop. The caspase-9 monomer consists of one large and one small subunit, both comprising the catalytic domain.
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At lower concentrations the equilibrium is on the side of the monomeric species. Both, dimer and monomer are co- coordinated by LiCl. At temperatures below -50°C LiCl gets separated from the magnesium amide in sense of a stable [LiCl]2 dimer solvated by four THF molecules. iPr-Turbo-Hauser Base in THF solution The solid state structure of TMPMgCl·LiCl remains almost completely in THF solution independently of temperature and concentration.
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CBI identifies the following uses: gasoline, anhydrous ammonia, vinyl chloride monomer (VCM), naphtha, propane, propylene, ethane, butane, NGL and butadiene. Cryogenic storage is also possible for LNG, methane, ethylene, hydrogen, and oxygen. Gases that may be stored include hydrogen, nitrogen, oxygen, helium and argon. Other uses have been applied to the Hortonsphere including space chambers, hyperbaric chambers, environmental chambers, vacuum vessels, process vessels, test vessels, containment vessels and surge vessels.
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The synthesis of poly(N-isopropylacrylamide) began with the synthesis of the acrylamide monomer by Sprecht in 1956. In 1957, Shearer patented the first application for what would be later identified as PNIPA for the use as a rodent repellent. Early work was piqued by theoretical curiosity of the material properties of PNIPA. The first report of PNIPA came in 1968, which elucidated the unique thermal behavior in aqueous solutions.
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The company produces by products of biodiesel and various specialty chemicals. Because these chemicals are produced from renewable feedstock, they can be considered "green" and sold for a premium in some markets. Chemicals listed include: Monomer Acid, Stearic, Dimer Acid, Printing Inks, Dimer-Based Polyamide Hot Melt Adhesive, Low Molecular Weight Liquor Polyamide Resins, Polyamide Hot-Melt Adhesive, Alcohol-soluble Polyamide Resins, Benzene-Soluble Polyamide Resins, and Bio Heating Fuel.
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This causative agent of tuberculosis expresses at least six different forms of epoxide hydrolase (forms A-F). The structure of epoxide hydrolase B reveals that the enzyme is a monomer and contains an alpha/beta hydrolase fold. In addition to providing insights into the enzyme mechanism, this hydrolase currently serves as a platform for rational drug design of potent inhibitors. In particular, urea based inhibitors have been developed.
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The actual amino acid sequence and total length differ between species, hence, the molecular weight. In most species it is 54 kDa in size. While it is only 44 kDa in Atlantic salmon. In chum salmon, the homodimer in joined by a single intermonomeric disulfide bond at Cys169. Each monomer in turn contains five intramonomeric disulfide bonds formed between Cys12-Cys26, Cys21-Cys41, Cys32-Cys81, Cys65-Cys95, and Cys102-Cys137.
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An example of a repressor protein is the methionine repressor MetJ. MetJ interacts with DNA bases via a ribbon-helix-helix (RHH) motif. MetJ is a homodimer consisting of two monomers, which each provides a beta ribbon and an alpha helix. Together, the beta ribbons of each monomer come together to form an antiparallel beta-sheet which binds to the DNA operator ("Met box") in its major groove.
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Models of polymer chains are split into two types: "ideal" models, and "real" models. Ideal chain models assume that there are no interactions between chain monomers. This assumption is valid for certain polymeric systems, where the positive and negative interactions between the monomer effectively cancel out. Ideal chain models provide a good starting point for investigation of more complex systems and are better suited for equations with more parameters.
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The term pre-polymer refers to a monomer or system of monomers that have been reacted to an intermediate molecular mass state. This material is capable of further polymerization by reactive groups to a fully cured high molecular weight state. As such, mixtures of reactive polymers with un-reacted monomers may also be referred to as pre-polymers. The term “pre-polymer” and “polymer precursor” may be interchanged.
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It is known that the reactivity of the monomer is lower than it could be, since the contained ester group can react with the reactive, polymerizing chain end and stabilize it. It therefore reacts significantly slower than other molecules without ester group. ECC polymerizes also much slower than radical monomers. It is therefore the object of research to find cationic polymerizable monomers with higher polymerization rate but same performance.
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It can be used to indicate whether reservoirs are built up and it is ideally close to 1. When the feed stops, its value is not defined. In semi-batch polymerisation, the instantaneous conversion is defined as the total mass of polymer divided by the total mass of monomer fed:Lazaridis et al.: "Semi-Batch Emulsion Copolymerization of Vinyl Acetate andButyl Acrylate Using Oligomeric Nonionic Surfactants", Macromol. Chem. Phys.
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The anionic ring-opening polymerization of ε-caprolactone, initiated by alkoxide Hexamethylcyclotrisiloxane is a cyclic monomer that is susceptible to anionic polymerization to siloxane polymers. Many cyclic compounds are susceptible to ring-opening polymerization. Epoxides, cyclic trisiloxanes, some lactones, lactides, cyclic carbonates, and amino acid N-carboxyanhydrides. In order for polymerization to occur with vinyl monomers, the substituents on the double bond must be able to stabilize a negative charge.
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Both KCC2 isoforms can form homomultimers, or heteromultimers with other K-Cl symporters on the cell membrane to maintain chloride homeostasis in neurons. Dimers, trimers, and tetramers involving KCC2 have been identified in brainstem neurons. Oligomerization may play an important role in transporter function and activation, as it has been observed that the oligomer to monomer ratio increases in correlation to the development of the chloride ion gradient in neurons.
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IPL consists of an intertwined dimer with two equal active sites. Each monomer has three helices, and both actives sites are composed of residues from each of the two monomers. A loop between the first and second helices provide an opening for the substrate to enter and product to exit. In that loop is a positively charged lysine at residue 42, which acts as a lid for this active site.
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2011.222 Polymerization reactions of the stable radical-containing monomer have also proved to be an area of difficulty in development. The stable organic radicals that are crucial to the functioning of the battery are sometimes consumed in side-reactions of various polymerization reactions. A research group has, however, successfully synthesized a cross-linked organic radical polymer while only losing 0.4% of the organic radicals in synthesis of the polymer.
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Both monomer and homodimer forms of IL-8 have been reported to be potent inducers of the chemokine receptors CXCR1 and CXCR2. The homodimer is more potent, but methylation of Leu25 can block the activity of homodimers. IL-8 is believed to play a role in the pathogenesis of bronchiolitis, a common respiratory tract disease caused by viral infection. IL-8 is a member of the CXC chemokine family.
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The thermodynamic parameters of this process have been measured. At temperatures above about 125 °C in the vapor phase, dissociation to cyclopentadiene monomer starts to become thermodynamically favored (the dissociation constant Kd = ). For instance, the values of Kd at 149 °C and 195 °C were found to be 277 and 2200, respectively. By extrapolation, Kd is on the order of 10–4 at 25 °C, and dissociation is disfavored.
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The changes interrupts the interaction of the alpha subunit with the beta–gamma complex and which results in a single alpha subunit with GTP bound and a beta–gamma dimer. The GTP–alpha monomer interacts with a variety of cellular targets. The beta–gamma dimer also can stimulate enzymes within the cells for example, adenylate cyclase but it does not have as many targets as the GTP–alpha complex.
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Phycocyanin (αβ) monomer Phycocyanin (αβ)6 hexamer Phycocyanin shares a common structural theme with all phycobiliproteins. The structure begins with the assembly of phycobiliprotein monomers, which are heterodimers composed of α and β subunits, and their respective chromophores linked via thioether bond. Each subunit is typically composed of eight α-helices. Monomers spontaneously aggregate to form ring- shaped trimers (αβ)3, which have rotational symmetry and a central channel.
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Dimethyldioxirane (DMDO), also referred to as Murray's reagent in reference to Robert W. Murray, is a dioxirane derived from acetone and can be considered as a monomer of acetone peroxide. It is a powerful yet selective oxidizing agent which finds use in organic synthesis. It is known only in the form of a dilute solution, usually in acetone, and hence the properties of the pure material are largely unknown.
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The dimeric titanium(III) complex reversibly dissociates to the monomer Cp2TiCl. This 15 electron species is Lewis acidic and thus binds epoxides and carbonyl compounds. The complex transfers a single electron to the coordinated substrate generating an alkyl centered radical and an oxygen bound titanium(IV) species. This process is driven by the strength of the titanium- oxygen bond, as well as strain release in the case of epoxides.
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Another factor in the effectiveness of smart polymers lies in the inherent nature of polymers in general. The strength of each molecule's response to changes in stimuli is the composite of changes of individual monomer units which, alone, would be weak. However, these weak responses, compounded hundreds or thousands of times, create a considerable force for driving biological processes. The pharmacy industry has been directly related to the polymer’s advances.
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CCP is the first heme enzyme to have its structure successfully solved through X-ray crystallography. The yeast enzyme is a monomer of molecular weight 34,000, containing 293 amino acids, and contains as well a single non-covalently bound heme b. It is negatively charged and is a moderately-sized enzyme (34.2 kDa). The apoenzyme, not active and bound to substrates, has an acidic isolelectric point of pH 5.0-5.2.
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Hemagglutinin esterase (HEs) is a glycoprotein that certain enveloped viruses possess and use as invading mechanism. HEs helps in the attachment and destruction of certain sialic acid receptors that are found on the host cell surface. Viruses that possess HEs include Influenza C virus, toroviruses, and coronaviruses (but not SARS-like coronaviruses). HEs is a dimer transmembrane protein consisting of two monomers, each monomer is made of three domains.
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SSI is a homodimer, in other words, it is made of two subunits which are exactly the same as each other. Each monomer contains 2 antiparallel beta-sheets and 2 short alpha-helices. Protease binding induces the widening of a channel-like structure, in which hydrophobic side-chains are sandwiched between 2 lobes. Studies have shown that the loss of the C-terminal domain reduces the inhibitory effect of the proteins.
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Ethylene-propylene rubber or EPDM added to polypropylene homopolymer increases its low temperature impact strength. Randomly polymerized ethylene monomer added to polypropylene homopolymer decreases the polymer crystallinity, lowers the melting point and makes the polymer more transparent. It is theoretically possible to add an agent that strengthens the fibers before they degrade too far to enable the removal of the mesh. This idea has not been tested or verified.
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DsRed is isolated from Discosoma sea anemones, and is a tetrameric protein. Most red fluorescent proteins come from DsRed. DsRed has low photostability (resistance to change under the influence of radiant energy or light) and a slow maturation rate (time until half the protein is folded). mRFP1 is derived from DsRed and is a monomer so it is smaller, but its quantum yield and photostability are less than that of DsRed.
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As early as 1936, Karl Ziegler proposed that anionic polymerization of styrene and butadiene by consecutive addition of monomer to an alkyl lithium initiator occurred without chain transfer or termination. Twenty years later, living polymerization was demonstrated by Szwarc through the anionic polymerization of styrene in THF using sodium naphthalenide as an initiator.Tatemoto, Masayoshi and Nakagawa, Tsuneo "Segmented polymers containing fluorine and iodine and their production" . Priority date 30 June 1976.
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An extended version of the 3c–2e bond model features heavily in cluster compounds described by the polyhedral skeletal electron pair theory, such as boranes and carboranes. These molecules derive their stability from having a completely filled set of bonding molecular orbitals as outlined by Wade's rules. Resonance structures of 3c-2e bond in diborane. The monomer BH3 is unstable since the boron atom has an empty p-orbital.
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Catechin-7-O-glucoside can be isolated from the hemolymph of the European pine sawfly (Neodiprion sertifer). It also occurs in relatively large quantities in cowpea (Vigna unguiculata) as the dominant flavan-3-ol monomer, and actually accounts for up to 70% of cowpea proanthocyanidins (tannins). It can also be produced by biotransformation of (+)-catechin by cultured cells of Eucalyptus perriniana.Biotransformation of (+)-catechin by plant cultured cells of Eucalyptus perriniana.
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Gannon, Joyce. Historical perspective: As Koppers Building marks 75 years, the iconic structure also marks changes in region. Pittsburgh Post-Gazette Sunday, November 14, 2004. In 1943, Koppers, at the US Government's behest, built a factory in Kobuta, Pennsylvania on the Ohio River downriver from Beaver, to manufacture styrene-butadiene monomer, a building block used to make a form of synthetic rubber for the World War II defense effort.
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The character of the backbone chain depends on the type of polymerization: in step-growth polymerization, the monomer moiety becomes the backbone, and thus the backbone is typically functional. These include polythiophenes or low band gap polymers in organic semiconductors. In chain-growth polymerization, typically applied for alkenes, the backbone is not functional, but bears the functional side chains or pendant groups. The character of the backbone, i.e.
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Cytochrome c Nitrite Reductase is a homodimer which contains five c-type heme cofactors per monomer. Four of the heme centers are bis- histidine ligated and presumably serve to shuttle electrons to the active site. The active site heme, however, is uniquely ligated by a single lysine residue. This enzyme belongs to the family of oxidoreductases, specifically those acting on other nitrogenous compounds as donors with a cytochrome as acceptor.
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Outer membrane protein G (OmpG) is a porin, a channel proteins in the outer membrane of Gram-negative bacteria. Escherichia coli OmpG forms a 14-stranded beta-barrel and in contrast to most porins, appears to function as a monomer. The central pore of OmpG is wider than other E. coli porins and it is speculated that it may form a non-specific channel for the transport of larger oligosaccharides.
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Glutathione reductase from human erythrocytes is a homodimer consisting of 52Kd monomers, each containing 3 domains. GR exhibits single sheet, double layered topology where an anti-parallel beta-sheet is largely exposed to the solvent on one face while being covered by random coils on the other face. This includes and NADPH-binding Domain, FAD-binding domain(s) and a dimerization domain. Each monomer contains 478 residues and one FAD molecule.
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Tantalum(III) chloride can form complexes with some ligands as a monomer or dimer. Complexes include Ta(=C-CMe3)(PMe3)2Cl3, [TaCl3(P(CH2C6H5)3THF]2μ-N2 and [TaCl3THF2]2μ-N2 (dinitrogen complexes). As a dimer, complexes include Ta2Cl6(SC4H8)3 (SC4H8=tetrahydrothiophene). Ta2Cl6(SMe2)3, Ta2Cl6(thiane)3 and Ta2Cl6(thiolane)3 have a double bond between the two tantalum atoms, and two bridging chlorides, and a bridging ligand.
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Editing also has several other function effects. Editing alters the maturation and assembly of the channel, with the unedited form having a tendency to tetramerize and then is transported to the synapse. However, the edited version is assembled as a monomer and resides mainly in the endoplasmic reticulum. The arginine residue in the pore loop of GluR-2 receptor is thought to belong to a retention signal for the endoplasmic reticulum.
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Extended crystal structure of GaBr3 The GaBr3 monomer has trigonal planar geometry, but when it forms the dimer Ga2Br6 the geometry around the Gallium center distorts to become roughly tetrahedral. As a solid, GaBr3 forms a monoclinic crystalline structure with a unit cell volume of 524.16 Å3. Additional specifications for this unit cell are as follows: a = 8.87 Å, b = 5.64 Å, c =11.01 Å, α = 90˚, β = 107.81˚, γ = 90˚.
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Thus far, the path integral approach didn't avail us of any novel results. For that, one must venture further than the ideal model. As a first departure from this limited model, we now consider the constraint of spatial obstructions. The ideal model assumed no constraints on the spatial configuration of each additional monomer, including forces between monomers which obviously exist, since two monomers cannot occupy the same space.
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Expanded polystyrene packaging A polystyrene yogurt container vacuum-formed cup; fine details such as the glass and fork food contact materials symbol and the resin identification code symbol are easily molded Polystyrene (PS) is a synthetic aromatic hydrocarbon polymer made from the monomer known as styrene. Polystyrene can be solid or foamed. General-purpose polystyrene is clear, hard, and rather brittle. It is an inexpensive resin per unit weight.
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Butadiene is then added and after styrene again its polymerization. The catalyst remains active during the whole process (for which the used chemicals must be of high purity). The molecular weight distribution of the polymers is very low (polydispersity in the range of 1.05, the individual chains have thus very similar lengths). The length of the individual blocks can be adjusted by the ratio of catalyst to monomer.
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Uridine monophosphate (UMP), also known as 5′-uridylic acid (conjugate base uridylate), is a nucleotide that is used as a monomer in RNA. It is an ester of phosphoric acid with the nucleoside uridine. UMP consists of the phosphate group, the pentose sugar ribose, and the nucleobase uracil; hence, it is a ribonucleotide monophosphate. As a substituent or radical its name takes the form of the prefix uridylyl-.
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Bromine atoms may also react directly with other radicals to help terminate the free radical chain- reactions that characterise combustion. To make brominated polymers and plastics, bromine-containing compounds can be incorporated into the polymer during polymerisation. One method is to include a relatively small amount of brominated monomer during the polymerisation process. For example, vinyl bromide can be used in the production of polyethylene, polyvinyl chloride or polypropylene.
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Spontaneous gradient polymerization is due to a difference in reactivity of the monomers. The resulting change in composition throughout the polymerization creates an inconsistent gradient along the polymer. Forced gradient polymerization involves varying the comonomer composition of the feed being throughout the reaction time. Because the rate of addition of the second monomer influences the polymerization and therefore properties of the formed polymer, continuous information about the polymer composition is vital.
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A diffractive beam splitter with three-dimensional structure created using nanoimprint lithography Nanoimprint lithography (NIL) is a method of fabricating nanometer scale patterns. It is a simple nanolithography process with low cost, high throughput and high resolution. It creates patterns by mechanical deformation of imprint resist and subsequent processes. The imprint resist is typically a monomer or polymer formulation that is cured by heat or UV light during the imprinting.
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The conformation assumed by a polymer chain in dilute solution can be modeled as a random walk of monomer subunits using a freely jointed chain model. However, this model does not account for steric effects. Real polymer coils are more closely represented by a self-avoiding walk because conformations in which different chain segments occupy the same space are not physically possible. This excluded volume effect causes the polymer to expand.
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According to CFSSP, the secondary structure of C1orf94 shows alpha Helix, extended strands, beta turns, and Random coils. Both Tertiary structures predicted by Phyre2 and the SWISS model show that C1orf94 is a monomer. According to I-TASSER the closest protein structures and Identified structural analogs to C1orf94 are 3IXZ (Pig gastric H+/K+-ATPase complexed with aluminum fluoride) and 3B8E (Crystal structure of the sodium-potassium pump).
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ParM is a prokaryotic actin homologue which provides the force to drive copies of the R1 plasmid to opposite ends of rod shaped bacteria before cytokinesis. ParM is a monomer that is encoded in the DNA of the R1 plasmid and manufactured by the host cell's ribosomes. In the cytoplasm it spontaneously polymerizes forming short strands that either bind to ParR or hydrolyze. ParR stabilizes ParM and prevents it from hydrolyzing.
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2,3,6,7,10,11-Hexahydroxytriphenylene, a building block for two-dimensional polymers Hexahydroxytriphenylene (HHTP) is any of a set of organic compounds consisting of a polycyclic aromatic hydrocarbon core—triphenylene—with six hydroxy group substituents attached to the rings. These compounds have found use as a component of two-dimensional polymers. The first covalent organic framework used this chemical as a monomer building block. It can be used for self-assembling metal–organic frameworks.
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Proline, however, is stabilized by multiple non- covalent interactions with this region. The enzyme structure is stabilized by hydrogen bonds, as well as crosslinking sulfide bonds between three pairs of cysteine residues (Cys22-Cys63, Cys56-Cys95, and Cys153-Cys200), analogous to many other papains. While the enzyme exists as a monomer in solution, crystallized zingibain forms tetramers, or dimers of dimers, linked by glycosylation chains on each subunit.
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Carnosinase in humans has two forms: 1\. Cellular, or tissue carnosinase: This form of the enzyme is found in every bodily tissue. It is a dimer, and hydrolyzes both carnosine and anserine, preferring dipeptides that have a histidine monomer in the C-terminus position. Tissue carnosinase is often considered a "nonspecific dipeptidase", based in part on its ability to hydrolyze a range of dipeptide substrates, including those belonging to prolinase. 2\.
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Expression of holin S at a precisely scheduled time after phage infection terminates respiration and allows release of a muralytic enzyme, endolysin, that hydrolyzes the cell wall. Point mutations in the S gene that prevent lethality alter TMSs 1 and 2 and the connecting loop. TMS 2 is particularly important for function. A three-step mechanism (monomer → dimer → oligomeric pore) has been proposed for assembly of the pore.
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Biodegradable polymers can be melt processed by conventional means such as compression or injection molding. Special consideration must be given to the need to exclude moisture from the material. Care must be taken to dry the polymers before processing to exclude humidity. As most biodegradable polymers have been synthesized by ring opening polymerization, a thermodynamic equilibrium exists between the forward polymerization reaction and the reverse reaction that results in monomer formation.
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Treatment in air at 100 °C for over 1000 hours will result in a minimal change in conductivity. Recently, it was reported that the conductivity of PEDOT:PSS can be improved to be more than 4600 S/cm. PEDOT:PSS is prepared by polymerizing EDT monomer in an aqueous solution of PSS using Na2S2O8 as the oxidizing agent. This aqueous solution is then spin coated and dried to make a film.
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In the radical telomerization of fluorotelomer molecules, a variety of fluorinated alkenes can serve as unsaturated taxogens including tetrafluoroethylene, vinylidene fluoride, chlorotrifluoroethylene, and hexafluoropropene. However, many fluorotelomers, such as fluorotelomer alcohols, are fluorocarbon-based because they are synthesized from tetrafluoroethylene. In addition to alcohols, synthetic products include fluorotelomer iodides, olefins, and acrylate monomer. Polymerized acrylate from iodide and alcohol monomers represent >80% of the global manufacture and use of fluorotelomer-based products.
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The biopolymers that comprise DNA, RNA and (poly)peptides are linear polymers (i.e.: each monomer is connected to at most two other monomers). The sequence of their monomers effectively encodes information. The transfers of information described by the central dogma ideally are faithful, deterministic transfers, wherein one biopolymer's sequence is used as a template for the construction of another biopolymer with a sequence that is entirely dependent on the original biopolymer's sequence.
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By far the most important application of 11-aminoundecanoic acid is its use as a monomer for polyamide 11 (also: nylon-11). Wallace Carothers, the inventor of polyamide (nylon 66), is said to have polymerized 11-aminoundecanoic acid as early as 1931.Renewable Polymers: Synthesis, Processing, and Technology, edited by V. Mittal, J. Wiley & Sons, Hoboken, NJ, 600px Although polyamide 11 is derived from a renewable raw material (i.e. biobased), it is not biodegradable.
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The capsules (often made of wax) around the monomer and the catalyst are important to maintain separation until the crack facilitates the reaction. In the capsule-catalyst system, the encapsulated healing agent is released into the polymer matrix and reacts with the catalyst, already present in the matrix. There are many challenges in designing this type of material. First, the reactivity of the catalyst must be maintained even after it is enclosed in wax.
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300px Polyurea is a type of elastomer that is derived from the reaction product of an isocyanate component and a synthetic resin blend component through step-growth polymerization. The isocyanate can be aromatic or aliphatic in nature. It can be monomer, polymer, or any variant reaction of isocyanates, quasi-prepolymer or a prepolymer. The prepolymer, or quasi- prepolymer, can be made of an amine-terminated polymer resin, or a hydroxyl- terminated polymer resin.
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However, the mechanism of how these additives reverse stereoselectivity is still being debated. There have been some challenges to the Ireland model, as it depicts the lithium species as a monomer in the transition state. In reality, a variety of lithium aggregates are often observed in solutions of lithium enolates, and depending on specific substrate, solvent and reaction conditions, it can be difficult to determine which aggregate is the actual reactive species in solution.
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Thexylborane is generated in situ. In solution, it isomerizes over the course several days to the 2,3-dimethyl-1-butyl derivative, shown as the monomer here: :Me2CHCMe2BH2 → Me2CHCH(Me)CH2BH2 Thexylborane allows the atom-economical synthesis of ketones from a pair of alkenes: :Me2CHCMe2BH2 \+ 2 RCH=CH2 → Me2CHCH(Me)CH2B(CH2CH2R)2 :Me2CHCH(Me)CH2B(CH2CH2R)2 \+ CO + H2O → OC(CH2CH2R)2 \+ ... The main point is that the thexyl group does not migrate.
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Diols react as alcohols, by esterification and ether formation. Diols such as ethylene glycol are used as co-monomers in polymerization reactions forming polymers including some polyesters and polyurethanes. A different monomer with two identical functional groups, such as a dioyl dichloride or dioic acid is required to continue the process of polymerization through repeated esterification processes. A diol can be converted to cyclic ether by using an acid catalyst, this is diol cyclization.
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The molecular and packing structures of collagen have eluded scientists over decades of research. The first evidence that it possesses a regular structure at the molecular level was presented in the mid-1930s. Since that time, research concentrated on the conformation of the collagen monomer, producing several competing models, although correctly dealing with the conformation of each individual peptide chain. The triple- helical "Madras" model provided an accurate model of quaternary structure in collagen.
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The effective moment rises to 4.1 μB at 4.3 K, due to ferromagnetic exchange interactions involving all three nickel ions. When bound to bulkier analogues of acetylacetonate ligand, steric hindrance favors formation of the mononickel derivatives. This behavior is observed for the derivative of 3-methylacetylacetonate.1\. A. Döhring, R. Goddard, P. W. Jolly, C. Krüger, V. R. Polyakov, "Monomer-Trimer Isomerism in 3-Substituted Pentane-2,4-dione Derivatives of Nickel(II)", Inorg.
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It will therefore be inaccessible to cellular substrates. In response to DNA damage, the kinase domain of one monomer phosphorylates ser-1981 of the other interacting ATM, resulting in subunit dissociation and ATM activation. The activated ATM triggers a sequence of events including cell cycle arrest which allows time for the repair of the damaged DNA. If damaged DNA is left unrepaired, it can lead to cell death or genomic instability, cancer and other pathologies.
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His method involves treating tri-O-phenylene bis-borate with diborane in a solution of either triglyme or tetraglyme. Brown claimed his method produces 85% yield of 97% pure product, catecholborane.New Economical, Convenient Procedures for the Synthesis of Catecholborane Unlike borane itself or alkylboranes, catechol borane exists as a monomer. This behavior is a consequence of the electronic influence of the aryloxy groups that diminish the Lewis acidity of the boron centre.
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In the gas phase, BeCl2 exists both as a linear monomer and a bridged dimer with two bridging chlorine atoms where the beryllium atom is 3-coordinate. The linear shape of the monomeric form is as predicted by VSEPR theory. The linear shape contrasts with the monomeric forms of some of the dihalides of the heavier members of group 2, e.g. CaF2, SrF2, BaF2, SrCl2, BaCl2, BaBr2, and BaI2, which are all non-linear.
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Having dry eyes for a while can lead to tiny abrasions on the surface of the eyes. In advanced cases, the epithelium undergoes pathologic changes, namely squamous metaplasia and loss of goblet cells. Some severe cases result in thickening of the corneal surface, corneal erosion, punctate keratopathy, epithelial defects, corneal ulceration (sterile and infected), corneal neovascularization, corneal scarring, corneal thinning, and even corneal perforation. Another contributing factor may be lacritin monomer deficiency.
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The ampliPHOX assay allows for the detection of biotin-labeled targets using light and a proprietary streptavidin-label (ampliTAG) to initiate the polymerization of a highly optimized monomer solution (ampliPHY). Transparent polymer is formed only on spots where a labeling event has occurred. The contrast of the polymer is enhanced by applying a simple stain (ampliRED) prior to imaging and analysis using the ampliVIEW software. Polymer spots formed are visible to the unaided eye.
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A schematic structure of a HIV-1 protease. The monomers are shown in green and cyan, the Asp-25 and Asp-25´ residues are shown in red, and Ile50 and Ile50´ residues linked to a water molecule are shown in purple. The HIV protease is a C2-symmetric homodimeric enzyme consisting of two 99 amino acid monomers. Each monomer contributes an aspartic acid residue that is essential for catalysis, Asp-25 and Asp-25´.
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26; 634–642. Each flexible flap contains three characteristic regions: side chains that extend outward (Met46, Phe53), hydrophobic chains extending inward (Ile47, Ile54), and a glycine rich region (Gly48, 49, 51, 52). Ile50 remains at the tip of the turn and when the enzyme is unliganded a water molecule makes hydrogen bonds to the backbone of Ile50 on each monomer. HIV proteases catalyze the hydrolysis of peptide bonds with high sequence selectivity and catalytic proficiency.
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Tetrafluorohydrazine is in equilibrium with its radical monomer nitrogen difluoride. : N2F4 2 NF2• At room temperature N2F4 is mostly associated with only 0.7% in the form of NF2 at 5mm Hg pressure. When the temperature rises to 225 °C, it mostly dissociates with 99% in the form of NF2. molecule dimensions and angles The energy needed to break the N-N bond in N2F4 is 20.8 kcal/mol, with an entropy change of 38.6 eu.
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Actin remodeling is a biochemical process in cells. In the actin remodeling of neurons, the protein actin is part of the process to change the shape and structure of dendritic spines. G-actin is the monomer form of actin, and is uniformly distributed throughout the axon and the dendrite. F-actin is the polymer form of actin, and its presence in dendritic spines is associated with their change in shape and structure.
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The protein of C11orf54 exists as a monomer in solution. The protein assumes a globular shape of 20 beta strands and 4 alpha helices, containing 9 antiparallel beta strands forming a beta screw region. The β-screw region of C11orf54 has structural similarity to the cyclic adenosine 3′,5′-monophosphate (cAMP) binding domain of the regulatory subunit of protein kinase A. A zinc ion is bound to the HxHxxxxxxxxxH motif found in the sequence.
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Acyclic diene metathesis or ADMET (distinguish from ADME) is a special type of olefin metathesis used to polymerize terminal dienes to polyenes: ADMET The new double bonds formed can be in cis- or trans-configurations. The exact ratio depends on the identities of the monomer and catalyst. ADMET is a type of step-growth, condensation polymerization. It should be distinguished from ring-opening metathesis polymerization (ROMP), which is a chain-growth, addition polymerization.
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The first base of the heptamer in the signal end is flipped out to avoid the clash in the active center. Each coding end of the nicked-RSS intermediate is stabilized exclusively by one RAG1-RAG2 monomer with non-specific protein-DNA interactions. The coding end is highly distorted with one base flipped out from the DNA duplex in the active center, which facilitates the hairpin formation by a potential two-metal ion catalytic mechanism.
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For this example above, once the 1H NMR has been integrated and the values have been normalized to 1, the degree of polymerization is calculated by simply dividing the normalized value for the repeat unit by the number of protons continued in the repeat unit. For this case, Xn = n = 100/2, and therefore Xn = 50, or there are 50 repeat units in this monomer. Example of utility of NMR for end group analysis.
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Four azurin molecules bind each p53 monomer with high affinity. The p53/azurin complex travels to the nucleus, where p53 upregulates the transcription of proapoptotic genes Bax and Noxa. P53 also activates the expression of cell- cycle inhibitors, preventing tumor cells from progressing beyond the G1 or S phase. Although this pathway plays a significant role in azurin’s anticancer activity, the details of the interaction between azurin and p53 are not well understood.
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Human alpha-2-macroglobulin is composed of four identical subunits bound together by -S-S- bonds. In addition to tetrameric forms of alpha-2-macroglobulin, dimeric, and more recently monomeric aM protease inhibitors have been identified. Each monomer of human alpha-2-macroglobulin is composed of several functional domains, including macroglobulin domains, a thiol ester-containing domain and a receptor-binding domain. Overall, alpha-2-Macroglobulin is the largest major nonimmunoglobulin protein in human plasma.
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Vinylene carbonate (VC) or 1,3-dioxol-2-one, is the simplest unsaturated cyclic carbonic acid ester. Vinylene carbonate can also be thought of as the cyclic carbonate of the hypothetical (Z)-ethene-1,2-diol. The activated double bond in this five-membered oxygen-containing heterocycle makes the molecule a reactive monomer for homopolymerization and copolymerization and a dienophile in Diels-Alder reactions. Below room temperature vinylene carbonate is a colorless stable solid.
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The preparation of higher molecular weight polymers with useful properties depends critically on the purity of the vinylene carbonate monomer. Vinylene carbonate can be homopolymerized in bulk, in solution, in suspension and in dispersion using radical initiators such as azobis(isobutyronitrile) (AIBN) or benzoyl peroxide. It can also be copolymerized with other vinyl monomers such as vinyl pyrrolidone or vinyl propionate. Polymerisation von Vinylencarbonat Polyvinylene carbonate is readily soluble in acetone and dimethylformamide.
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Most transporters have transmembrane domains that consist of a total of 12 α-helices with 6 α-helices per monomer. Since TMDs are structurally diverse, some transporters have varying number of helices (between six and eleven). The TM domains are categorized into three distinct sets of folds: type I ABC importer, type II ABC importer and ABC exporter folds. The classification of importer folds is based on detailed characterization of the sequences.
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In 2016, OSTE Polymers were shown to possess a unique photolitography mechanism, based on diffusion-induced monomer depletion, which enables high photostructuring accuracy. The OSTE polymer material was originally invented at the KTH Royal Institute of Technology, but is now sold by Mercene Labs. Whereas the material has properties similar to those of SU8, OSTE has the specific advantage that it contains reactive surface molecules, which make this material attractive for microfluidic or biomedical applications.
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A tetrapeptide, a hetero-oligomer of the amino acids valine (green), glycine (black), serine (black), and alanine (blue). The units were joined by condensation of the carboxylic acid group –C(=O)OH of one monomer with the amine group of the next one. Some biologically important oligomers consist of macromolecules like proteins or nucleic acids; for instance, hemoglobin is a protein tetramer. An oligomer of amino acids is called an oligopeptide or just a peptide.
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The box represents a vacant (or extremely labile) coordination site. Step i involves binding of the monomer to the metal and step ii involves the migratory insertion step. These steps, which alternate from one side of the metal center to the other, are repeated many times for each polymer chain. The details of this mechanism can be used to explain the stereoregularity of the polymerisation of alkenes using Ziegler–Natta or metallocene catalysts.
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Pseudomonas aeruginosa causes severe infections in humans and is labeled as a critical threat by the World Health Organization because of its resistance to multiple therapies. The glyoxylate shunt is essential for Pseudomonas aeruginosa growth in a host organism. In 2017, McVey, et al. examined the 3D structure of P. aeruginosa malate synthase G. They found that it is a monomer composed of four domains and is highly conserved in other pathogens.
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Elastin is a fibrous protein common in various soft tissues, like skin, blood vessels and lung tissue. Each monomer connects with each other, forming a 3D network, with ability to endure over 200% strain before deformation. Keratin is a structural protein mainly found in hair, nails, hooves, horns, quills. Basically keratin is formed by polypeptide chains, which coil into α-helices with sulfur cross-links or bond into β-sheets linked by hydrogen bonding.
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Airbath (part of Reva Industries) is in north-east Hull. Fenner Dunlop Europe who claim to be the world's largest conveyor belt manufacturer, in Marfleet, have their own cricket pitch and their Hainsworth Research Centre. BP Saltend (in Preston) is Europe's largest producer of acetic acid, and part of the worldwide BP Acetyls group; next door, Ineos Enterprises makes vinyl acetate monomer (VAM) and Vivergo (bioethanol) is nearby. Fenner PLC is in Hessle.
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Upon heating, itaconic anhydride isomerizes to citraconic acid anhydride, which can be hydrolyzed to citraconic acid (2-methylmaleic acid). Steps in conversion of citric acid to citraconic acid via itaconic and aconitic acids. Partial hydrogenation of itaconic acid over Raney nickel affords 2-methylsuccinic acid. Itaconic acid is primarily used as a co-monomer in the production of acrylonitrile butadiene styrene and acrylate latexes with applications in the paper and architectural coating industry.
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440x440px Polymerization is the process of combining many small molecules known as monomers into a covalently bonded chain or network. During the polymerization process, some chemical groups may be lost from each monomer. This happens in the polymerization of PET polyester. The monomers are terephthalic acid (HOOCC6H4COOH) and ethylene glycol (HOCH2CH2OH) but the repeating unit is OCC6H4COOCH2CH2O, which corresponds to the combination of the two monomers with the loss of two water molecules.
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Each molybdenum has local octahedral symmetry and two chlorides bridge between the molybdenum centers. A similar structure is also found for the pentachlorides of W, Nb and Ta. In the gas phase and partly in solution, the dimers partially dissociates to give a monomeric pentahalide. The monomer is paramagnetic, with one unpaired electron per Mo center, reflecting the fact that the formal oxidation state is +5, leaving one valence electron on the metal center.
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As of late 2019, three structures have been solved for this class of enzymes, with the PDB accession codes , , and . They show that the N-acylglucosamine 2-epimerase monomer folds as a barrel composed of α-helices, in a manner known as (α/α)6-barrel. The structures are presented as dimers, with the structures from Sus scrofa and Anabaena sp. CH1 having a different organization than the structure from Nostoc sp. KJV10.
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Poly(3,4-ethylenedioxythiophene)-tetramethacrylate or PEDOT-TMA is a p-type conducting polymer based on 3,4-ethylenedioxylthiophene or the EDOT monomer. It is a modification of the PEDOT structure. Advantages of this polymer relative to PEDOT (or PEDOT:PSS) are that it is dispersible in organic solvents, and it is non-corrosive. PEDOT-TMA was developed under a contract with the National Science Foundation, and it was first announced publicly on April 12, 2004.
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TOP1 and TOP2 have shown a capacity to interact with salicylic acid and mediate SA activity in the system. In vitro experiments have shown that when these enzymes are not present or defective, the vulnerability to pathogen infection is higher. TOPs proteolytic activity is affected by their monomer/dimer relation. Oxidative environment increases the dimer form and result in proteolytic activity inhibition while reducing environments, stimulate accumulation of monomers and then favor TOP enzymes activity.
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They are bound to the protein scaffold via chelation of their central magnesium atom either to amino acids of the protein (mostly histidine) or water-bridged oxygen atoms (only one BChl a of each monomer). Since the structure is available, calculating structure-based optical spectra is possible for comparison with experimental optical spectra. In the simplest case only the excitonic coupling of the BChls is taken into account. More realistic theories consider pigment-protein coupling.
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This hydrophobic core and its interactions lock the shape of the enzyme even though the enzyme is a dynamic structure. There is also evidence to support that the structure of the enzyme is conserved, meaning the structure takes sharp turns in order to take up less space. The cleft in the shikimate dehydrogenase monomer. The green selection is the loops surrounding the cleft, and the red selection shows alpha helices in the background.
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This structure is key to its lubricating ability, which is ascribed to interchain repulsion. This leads to trapping of large quantities of solvent and the stabilization of a fluid-like cushioning layer, which enables bottle brush polymers to lower the friction between joints when external pressure is applied. Furthermore, lubricin's N-terminus is thought to create disulfide bonds between two lubricin monomers. The glycoprotein thus exists as both a monomer and a dimer.
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The binding interaction between collagen and MDP was studied by saturation transfer difference (STD) NMR spectroscopy. The STD results imply that MDP has a relatively stable interaction with the collagen, because of the hydrophobic interactions between the hydrophobic MDP moieties and the hydrophobic collagen surface.N. Hiraishi, N. Tochio, T. Kigawa, M. Otsuki, and J. Tagami, “Monomer-Collagen Interactions Studied by Saturation Transfer Difference NMR”, J Dent Res 92(3):284-288 (2013).
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PGHS exists as a symmetric homodimer, each monomer of which consists of 3 domains: an N-terminal epidermal growth factor (EGF) like module; a membrane-binding domain; and a large C-terminal catalytic domain containing the cyclooxygenase and the peroxidase active sites. The catalytic domain shows striking structural similarity to MPO. The image at the top of this page is an example of Myeloperoxidase 1dnu derived from X-ray diffraction with resolution 1.85 angstrom.
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In vitro the ParM monomer has been observed polymerizing both with ATP and with GTP, but experiments by Popp et al. seem to indicate that the reaction "prefers" GTP and that GTP is the nucleotide that most likely makes the significant contributions in the cell. For the remainder of this article GTP will be assumed to be the active nucleotide although many experiments have used ATP instead. ParM binds and hydrolyzes GTP as it polymerizes.
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A study by Garner and Campbell has suggested that the unit at the end of the ParM strand must have GTP bound to maintain the stability of the polymer. If one of the ends has the GDP bound version the polymer strand depolymerizes very quickly into its constituent monomer units. This is suggested by their experiment in which they cut growing ParM polymer strands exposing ADP bound ends. Once cut the strands quickly hydrolyzed.
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Nanoimprint lithography (NIL), and its variants, such as Step-and-Flash Imprint Lithography and laser assisted directed imprint (LADI) are promising nanopattern replication technologies where patterns are created by mechanical deformation of imprint resists, typically monomer or polymer formations that are cured by heat or UV light during imprinting. This technique can be combined with contact printing and cold welding. Nanoimprint lithography is capable of producing patterns at sub-10 nm levels.
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The integration of HIV DNA can occur either in dividing or resting cells, and the HIV integrase enzyme can exist in the form of a monomer, dimer, tetramer, and possibly even higher-order forms (such as octomers). Each HIV particle has an estimated 40 to 100 copies of the integrase enzyme. Integrase functions are unique to retroviruses; human cells are not required to cut-and- paste pieces of DNA into the genome.
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GvpA of Halobacterium salinarum is a 76 amino acid long 8 kDa hydrophobic monomer. Gas vesicles are hollow cylindrical tubes, closed by a hollow, conical cap at each end. Both the conical end caps and central cylinder are made up of 4-5 nm wide ribs that run at right angles to the long axis of the structure. Gas vesicles seem to be constituted of two different protein components, GVPa and GVPc.
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Hexamethylenediamine is used almost exclusively for the production of polymers, an application that takes advantage of its structure. It is difunctional in terms of the amine groups and tetra functional with respect to the amine hydrogens. The great majority of the diamine is consumed by the production of nylon 66 via condensation with adipic acid. Otherwise hexamethylene diisocyanate (HDI) is generated from this diamine by Phosgenation as a monomer feedstock in the production of polyurethane.
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Neuroglobin is a member of the vertebrate globin family involved in cellular oxygen homeostasis and reactive oxygen/nitrogen scavenging. It is an intracellular hemoprotein expressed in the central and peripheral nervous system, cerebrospinal fluid, retina and endocrine tissues. Neuroglobin is a monomer that reversibly binds oxygen with an affinity higher than that of hemoglobin. It also increases oxygen availability to brain tissue and provides protection under hypoxic or ischemic conditions, potentially limiting brain damage.
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Lysenin is a pore-forming toxin (PFT) present in the coelomic fluid of the earthworm Eisenia fetida. Pore-forming toxins are a group of proteins that act as virulence factors of several pathogenic bacteria. Lysenin proteins are chiefly involved in the defense against eukaryotic and prokaryotic pathogens. Following the general mechanism of action of PFTs lysenin is segregated as a soluble monomer that binds specifically to a membrane receptor, sphingomyelin in the case of lysenin.
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As shown, different ligands bind either the allosteric or the catalytic subunit. Allosteric subunit binds a non-substrate, activating FA (e.g., palmitic acid). The allosteric subunit with bound fatty acid activates the catalytic subunit by decreasing the Km for AA. PTGS2 (COX-2) exists as a homodimer, each monomer with a molecular mass of about 70 kDa. The tertiary and quaternary structures of PTGS1 (COX-1) and PTGS2 (COX-2) enzymes are almost identical.
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Ziegler–Natta scheme A variety of methods have been developed to synthesize polyacetylene, from pure acetylene and other monomers. One of the most common methods uses a Ziegler–Natta catalyst, such as Ti(OiPr)4/Al(C2H5)3, with gaseous acetylene. This method allows control over the structure and properties of the final polymer by varying temperature and catalyst loading. Mechanistic studies suggest that this polymerization involves metal insertion into the triple bond of the monomer.
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The ETFDH gene is located on the q arm of chromosome 4 in position 32.1 and has 13 exons spanning 36,613 base pairs. The protein is synthesized as a 67-kDa precursor which is targeted to mitochondria and processed in a single step to a 64-kDa mature form located in the mitochondrial membrane. This 64-kDA mature form is a monomer integrated into the mitochondrial inner membrane, containing a 4Fe-4S cluster and 1 molecule of FAD.
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Once the whole complex is completed the system switches to secreting proteins that are intended to be delivered into host cells. The needle is presumed to be built from bottom to top; units of needle monomer protein pile upon each other, so that the unit at the tip of the needle is the last one added. The needle subunit is one of the smallest T3SS proteins, measuring at around 9 kDa. 100−150 subunits comprise each needle.
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Active caspase-9 works as an initiating caspase by cleaving, thus activating downstream executioner caspases, initiating apoptosis. Once activated, caspase-9 goes on to cleave caspase-3, -6, and -7, initiating the caspase cascade as they cleave several other cellular targets. When caspase-9 is inactive, it exists in the cytosol as a zymogen, in its monomer form. It is then recruited and activated by the CARDs in apaf-1, recognizing the CARDs in caspase-9.
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The four domains of rabbit muscle phosphoglucomutase, drawn from . Green = Domain I, Blue = Domain II, Red = Domain III, Yellow = Domain IV. Pink residue = Serine 116. While rabbit muscle phosphoglucomutase has served as the prototype for much of the elucidation of this enzyme's structure, newer bacterium- derived crystal structures exhibit many of the same defining characteristics. Each phosphoglucomutase monomer can be divided into four sequence domains, I-IV, based on the enzyme’s default spatial configuration (see image at right).
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INEOS bought out the vinyl acetate monomer (VAM) and Ethyl acetate (ETAC) plants from BP in March 2007. The VAM plant was closed down in 2013 with the loss of 18 jobs. INEOS had invested £40 million in the plant but it couldn't make a profit against cheaper imports from the United States and Saudi Arabia. The Ethyl acetate (ETAC) is still in production with ETAC being used in printing inks, glues, paints, packaging, cosmetics and pharmaceuticals.
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Different portions of the sugar molecules are used for biosynthesis based on the metabolic pathway an organism uses. Therefore, any interpretations of position-specific isotopes of molecules downstream of glucose have to consider this intramolecular heterogeneity. Glucose is the monomer of cellulose, the polymer that makes plants and trees rigid. After the advent of position-specific analyses of glucose, biogeochemists from Sweden looked the concentric tree rings of a Pinus nigra that recorded yearly growth between 1961 and 1995.
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Radicals can undergo a disproportionation reaction through a radical elimination mechanism (See Fig. 1). Here a radical abstracts a hydrogen atom from another same radical to form two non-radical species: an alkane and an alkene. Radicals can also undergo an elimination reaction to generate a new radical as the leaving group. For example, when polystyrene decomposes upon heating at a temperature above 300°C, a styrene monomer is generated via a radical elimination mechanism (See Fig. 2).
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Isocitrate dehydrogenase is composed of 3 subunits, allosterically regulated, and requires an integrated Mg2+ or Mn2+ ion. The mitochondrial form of IDH, like most isoforms, is a homodimer, in which two identical monomer subunits form one unit. The structure of Mycobacterium tuberculosis IDH-1 bound with NADPH and Mn2+ has been solved by X-ray crystallography. It is a homodimer in which each subunit has a Rossmann fold, and a common top domain of interlocking β sheets.
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There are various methods used to form polymeric macromolecular cages. One synthetic method uses ring opening and multiple click chemistry in the first step to form trefoil and quatrefoil-shaped polymers, which can then be topologically converted into cages using hydrogenolysis. The initiator in this synthesis is azido and hydroxy functionalized p-xylene and the monomer is butylene oxide. The ring opening polymerization and simultaneous click cyclizations of butylene oxide with the initiator is catalyzed by t-Bu-P4.
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Nafion derivatives are first synthesized by the copolymerization of tetrafluoroethylene (TFE) (the monomer in Teflon) and a derivative of a perfluoro (alkyl vinyl ether) with sulfonyl acid fluoride. The latter reagent can be prepared by the pyrolysis of its respective oxide or carboxylic acid to give the olefinated structure. The resulting product is an -SO2F-containing thermoplastic that is extruded into films. Hot aqueous NaOH converts these sulfonyl fluoride (-SO2F) groups into sulfonate groups (-SO3−Na+).
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Moreover, the top-down approach is applicable to mainly only silicon based technology, and is unable to be used for biological developments. The peptide structure is organized hierarchically into four levels. The primary structure of a peptide is the sequence of the amino acids on the peptide chain. Amino acids are monomer molecules that carries a carboxyl and an amine functional groups; a spectrum of other chemical groups are attached to different amino acids, such as thiols and alcohols.
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In the diagram below, consider the amino-acids as single aliphatic monomers reacting with identical molecules to form a polyamide, focusing on solely the amine and acid groups. Ignore the substituent R groups - under the assumption the difference between the R groups are negligible: The reaction of two amino acids. Many of these reactions produce long chain proteins For fully aromatic polyamides or 'aramids' e.g. Kevlar, the more reactive acyl chloride is used as a monomer.
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Group-transfer polymerization, like rhodium- catalyzed polymerization of PTMA, allows for polymerization of nitroxyl radical monomers. Unlike rhodium-catalyzed monomers, group-transfer polymerization utilizes silicon to catalyze the polymerization. Synthesis of 4-Methacryloxyloxy-TEMPO Monomers Preparation of the monomer, 4-methacryloxyloxy-TEMPO can be accomplished by acylation of 4-hydroxy-TEMPO with methacryloyl chloride. GTP polymerization of PTMA Polymerization using 1-methoxy-2-methyl-1trimethylsilyloxy-propene (MTS) as a catalyst proceeds rapidly at room temperature to form PTMA.
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Stress fibers are primarily composed of actin and myosin. Actin is a ~43kDa globular protein, and can polymerize to form long filamentous structures. These filaments are made of two strands of actin monomers (or protofilaments) wrapping around each other, to create a single actin filament. Because actin monomers are not symmetrical molecules, their filaments have polarity based upon the structure of the actin monomer, which will allow one end of the actin filament to polymerize faster than the other.
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E.H. Roelfzema is the pen name of Erik Hazelhoff Roelfzema Jr. (February 17, 1947, The Hague - February 11, 2010, Kockengen), Dutch artist, writer, poet, lyricist and musician. In his art he used encaustic techniques, as well as polymer resin (glass panels), and monomer resin (embeddings). He travelled extensively, and from 1970 until 1990 he lived in Ahualoa, Hawaii, working as a farmer and fisherman, and surfing. He returned to the Netherlands in 1990 and married photographer Patricia Steur.
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Transcription factor RFX3 is a protein that in humans is encoded by the RFX3 gene. This gene is a member of the regulatory factor X gene family, which encodes transcription factors that contain a highly-conserved winged helix DNA binding domain. The protein encoded by this gene is structurally related to regulatory factors X1, X2, X4, and X5. It is a transcriptional activator that can bind DNA as a monomer or as a heterodimer with other RFX family members.
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Protein structure is the three-dimensional arrangement of atoms in an amino acid-chain molecule. Proteins are polymers specifically polypeptides formed from sequences of amino acids, the monomers of the polymer. A single amino acid monomer may also be called a residue indicating a repeating unit of a polymer. Proteins form by amino acids undergoing condensation reactions, in which the amino acids lose one water molecule per reaction in order to attach to one another with a peptide bond.
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Resin casting is a method of plastic casting where a mold is filled with a liquid synthetic resin, which then hardens. It is primarily used for small- scale production like industrial prototypes and dentistry. It can be done by amateur hobbyists with little initial investment, and is used in the production of collectible toys, models and figures, as well as small-scale jewellery production. The synthetic resin for such processes is a monomer for making a plastic thermosetting polymer.
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About 70% of polybutadiene is used in tire manufacturing Polybutadiene [butadiene rubber BR] is a synthetic rubber. Polybutadiene rubber is a polymer formed from the polymerization of the monomer 1,3-butadiene. Polybutadiene has a high resistance to wear and is used especially in the manufacture of tires, which consumes about 70% of the production. Another 25% is used as an additive to improve the toughness (impact resistance) of plastics such as polystyrene and acrylonitrile butadiene styrene (ABS).
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Structural formula of PEDOT Structural formula of PEDOT:PSS Poly(3,4-ethylenedioxythiophene), abbreviated PEDOT or PEDT is a conducting polymer based on 3,4-ethylenedioxythiophene or EDOT monomer. PEDOT is polarized by the oxidation of EDOT with catalytic amounts of iron (III) sulfate. The re-oxidation of iron is given by Sodium persulfate. Advantages of PEDOT are optical transparency in its conducting state, non toxic, stable up to temperatures of 280 °C and a conductivity up to 500 S/m.
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Polymeric micelles are drug carriers formed by the aggregation of some amphiphilic molecule with an amphiphilic block copolymer. These carriers form at some high concentration specific to the compounds used, called the critical micelle concentration. The addition of an amphiphilic block copolymer effectively lowers this critical micelle concentration by shifting the monomer exchange equilibrium. These carriers are comparable to liposomes, however the lack of an aqueous core makes polymeric micelles less accommodating to a wide variety of drugs.
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The large domain in the eukaryotic form also contains a histidine that is essential for tetramer stability. All four histidines of these residues, one from each monomer, sit at the center of the tetrameric complex, where two histidines from a dimeric subunit engages in stacking interactions with the histidines of the other subunit. Prokaryotic SHMT has a proline residue rather than histidine in the equivalent position, which would in part explain why prokaryotic SHMT does not form tetramers.
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Azurin is a small, periplasmic, bacterial blue copper protein found in Pseudomonas, Bordetella, or Alcaligenes bacteria. Azurin moderates single- electron transfer between enzymes associated with the cytochrome chain by undergoing oxidation-reduction between Cu(I) and Cu(II). Each monomer of an azurin tetramer has a molecular weight of approximately 14kDa, contains a single copper atom, is intensively blue, and has a fluorescence emission band centered at 308 nm. Azurins and pseudoazurins participate in the denitrification processes in bacteria.
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2‑oxazoline to poly(2‑oxazoline) In Living cationic ring-opening polymerization the monomer is a heterocycle such as an epoxide, THF, an oxazoline or an aziridine such as t-butylaziridine.E.J. Goethals , Beatrice Verdonck in Living and controlled polymerization Joseph Jagur-Grodzinski, ed. (2005) The propagating species is not a carbocation but an oxonium ion. Living polymerization is more difficult to achieve because of the ease of termination by nucleophilic attack of a heteroatom in the growing polymer chain.
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SP-A2 is a protein of 248 amino acids usually found in large oligomeric structures. The mature SP-A2 monomer is a 35kDa protein that differs from SP-A1 in four amino acids at the coding region. The structure of SP-A2 monomers consists of four domains: an N-terminal, a collagen-like domain, a neck region, and a carbohydrate recognition domain. The C-terminal carbohydrate recognition domain (CRD) allows binding to various types of microorganisms and molecules.
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Rhodocene exists as [Rh(C5H5)2], a paramagnetic 19-valence electron radical monomer only at or below −196 °C (liquid nitrogen temperatures) or above 150 °C in the gas phase. It is this monomeric form that displays the typical staggered metallocene sandwich structure. At room temperature (25 °C), the lifetime of the monomeric form in acetonitrile is less than two seconds; and rhodocene forms [Rh(C5H5)2]2, a diamagnetic 18-valence electron bridged dimeric ansa-metallocene structure.
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Heat shock factors (HSF) are transcriptional activators of heat shock genes. These activators bind specifically to Heat Shock sequence Elements (HSE) throughout the genome whose consensus-sequence is a tandem array of three oppositely oriented "AGAAN" motifs or a degenerate version thereof. Under non-stressed conditions, Drosophila HSF is a nuclear-localized unbound monomer, whereas heat shock activation results in trimerization and binding to the HSE. The Heat Shock sequence Element is highly conserved from yeast to humans.
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Micromotors and nanomotors can also move preferentially in the direction of externally applied chemical gradients, a phenomenon defined as chemotaxis. Chemotaxis has been observed in self-propelled Au-Pt nanorods, which diffuse towards the source of hydrogen peroxide, when placed in a gradient of the chemical. Silica microparticles with Grubbs catalyst tethered to them, also move towards higher monomer concentrations. Enzymes also behave as nanomotors and migrate towards regions of higher substrate concentration, which is known as enzyme chemotaxis.
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Glycolic acid is a useful intermediate for organic synthesis, in a range of reactions including: oxidation-reduction, esterification and long chain polymerization. It is used as a monomer in the preparation of polyglycolic acid and other biocompatible copolymers (e.g. PLGA). Commercially, important derivatives include the methyl (CAS# 96-35-5) and ethyl (CAS# 623-50-7) esters which are readily distillable (boiling points 147–149 °C and 158–159 °C, respectively), unlike the parent acid. The butyl ester (b.p.
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The Cossee–Arlman mechanism in polymer chemistry is the main pathway for the formation of C–C bonds in the polymerization of alkenes. The mechanism features an intermediate coordination complex that contains both the growing polymer chain and the monomer (alkene). These ligands combine within the coordination sphere of the metal to form a polymer chain that is elongated by two carbons.Hartwig, J. F. Organotransition Metal Chemistry, from Bonding to Catalysis; University Science Books: New York, 2010.
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Some researches have suggested that the dimeric structure is critical for enzymatic activity. It was first proposed that the reciprocating compulsory ordered mechanism where each subunit alternates as the active and the helper subunit, but both are needed for activity. This mechanism predicts an inactive monomer, and was corroborated by studies that showed a dramatic reduction of enzymatic activity. Studies with mitochondrial MDH2 have shown that this enzyme is allosterically regulated as a complex as well.
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Thus, some are found in plasma membranes while others are in organellar membranes such as vacuoles of plants and yeast and the golgi of animals. They catalyze cation:proton antiport, have a single essential zinc- binding site within the transmembrane domains of each monomer within the dimer, and have a binuclear zinc-sensing and binding site in the cytoplasmic C-terminal region. A representative list of proteins belonging to the CDF family can be found in the Transporter Classification Database.
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The FBO molecule is linear with structure F-B=O. The F-B bond length is 1.283 Å, and B-O bond is 1.207 cm−1Å. The infrared spectrum of BFO has vibrational bands at 1900, 1050, and 500 cm−1. Spectroscopic constants of the 10BFO molecule are B=9349.2711 MHz D=3.5335 kHz and for 11BFO molecule they are B=9347.3843 MHz D=3.5273 kHz The monomer is stable either at low pressures, or temperatures over 1000 °C.
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By definition, a crosslinked polymer gel is a macromolecule that cannot dissolve. Due to the polymeric domains created by crosslinking, in the gel microstructure, hydrogels are not homogenous within the solvent system in which they are placed into. Swelling of the network, however, does occur in the presence of a proper solvent. Voids in the microstructure of the gel where crosslinking agent or monomer has aggregated during polymerization can cause solvent to diffuse into or out of the hydrogel.
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The Naja Kaouthia venom is a member of the snake three-finger toxin family in the subfamily type II alpha-neurotoxin. The lethal dose (LD50) of α-cobratoxin is 0,1 mg/kg by intravenous injection into mice15. The toxin occurs as a monomer but can form a homodimer or heterodimers with cytotoxins 1,2, and 3 through disulfide linkage. The monomeric form can bind with high affinity to muscular, Torpedo, and neuronal alpha-7 nicotinic acetylcholine receptors (nAChR).
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Trimethylolpropane triacrylate (TMPTA) is a trifunctional acrylate ester monomer used in the manufacture of plastics, adhesives, acrylic glue, anaerobic sealants, and ink. It is useful for its low volatility and fast cure response. It has the properties of weather, chemical and water resistance, as well as good abrasion resistance. End products include alkyd coatings, compact discs, hardwood floors, concrete polymers, Dental composites, photolithography, letterpress, screen printing, elastomers, automobile headlamps, acrylics and plastic components for the medical industry.
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Such step polymerizations require highly pure monomer and precise stoichiometry to ensure high molecular weight products. DCDPS is the precursor to polymers known as Udel (from bisphenol A), PES, and Radel R. Udel is a high-performance amorphous sulfone polymer that can molded into a variety of different shapes. It is both rigid and temperature-resistant, and has applications in everything from plumbing pipes, to printer cartridges, to automobile fuses. DCDPS also reacts with bisphenol S to form PES.
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The goal of engineering for free radical copolymerization is to have F_1 = f_1 over a broad range of conversion. For commercial applications, copolymer composition must be consistent across the aggregate. Batch reactors have no control over composition drift and require the implementation of engineering solutions to limit drift. Some possible reactor engineering solutions include: # Semibatch reactor or fed-batch reactor: by adding the monomer that is preferentially consumed at the reaction rate, f_1 can be held constant and maintained.
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Under certain conditions, one can convert primary amines into isothiocyanates. CSCl2 also serves as a dienophile to give, after reduction 5-thiacyclohexene derivatives. Thiophosgene is also known as the appropriate reagent in Corey- Winter synthesis for stereospecific conversion of 1,2-diols into olefins. It forms a head-to-tail dimer upon irradiation with UV light: :2 CSCl2 → S2(CCl2)2 Unlike thiophosgene monomer, a red liquid, the photodimer, an example of a 1,3-dithietane, is a colorless solid.
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The crystallographic structure of p11 protein tetramer. Disulfide bonds between the pair of dimers (cyan and green) is represented by yellow sticks. The N-terminus of annexin II is magenta colored. The p11 protein can be found as a free monomer, a homodimer, or a heterotetramer composed of a p11 dimer complex with two molecules of annexin II. The homodimer or heterotetramer can, in turn, dimerize through formation of two disulfide bonds (see figure to the left).
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Polystyrene was discovered in 1839 by Eduard Simon, an apothecary from Berlin.Simon, E. (1839) "Ueber den flüssigen Storax (Styrax liquidus)" [On liquid storax (Styrax liquidus)], Annalen der Chemie, 31 : 265–277. From storax, the resin of the Oriental sweetgum tree Liquidambar orientalis, he distilled an oily substance, a monomer that he named styrol. Several days later, Simon found that the styrol had thickened into a jelly he dubbed styrol oxide ("Styroloxyd") because he presumed an oxidation.
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Upon treatment with aldehydes, bilanes may cyclize to give porphyrinogens and various open or closed oligomers and polymers. In living organisms, the biosynthesis of all natural porphyrins proceeds through the bilane preuroporphyrinogen, which is produced from four molecules of the monomer porphobilinogen, and then converted to the closed tetrapyrrole uroporphyrinogen III (or, in certain metabolic disorders, into uroporphyrinogen I). Also, the catabolism of hemoglobin in humans produces bilirubin, another linear tetrapyrrole that is a partially oxidized bilane.
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Polysilicon halides are silicon-backbone polymeric solids. At room temperature, the polysilicon fluorides are colorless to yellow solids while the chlorides, bromides, and iodides are, respectively, yellow, amber, and red-orange.Inorganic Chemistry, Holleman-Wiberg, Academic Press (2001), p. 850. Polysilicon dihalides (perhalo-polysilenes) have the general formula (SiX2)n while the polysilicon monohalides (perhalo-polysilynes) have the formula (SiX)n, where X is F, Cl, Br, or I and n is the number of monomer units in the polymer.
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In the yeast strain Pichia pastoris, lysyl oxidase constitutes a homodimeric structure. Each monomer consists of an active site that includes a Cu(II) atom coordinated with three histidine residues as well as 2,4,5-trihydroxyphenalanine quinone (TPQ), a crucial cofactor. In humans, the LOX gene is located on chromosome 5 q23.3-31.2. The DNA sequence encodes a polypeptide of 417 amino acids, the first 21 residues of which constitute a signal peptide, with a weight of approximately 32 kDa.
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There are two main types of primase: DnaG found in most bacteria, and the AEP (Archaeo-Eukaryote Primase) superfamily found in archaean and eukaryotic primases. While bacterial primases (DnaG-type) are composed of a single protein unit (a monomer) and synthesize RNA primers, AEP primases are usually composed of two different primase units (a heterodimer) and synthesize two-part primers with both RNA and DNA components. While functionally similar, the two primase superfamilies evolved independently of each other.
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When caprolactam is heated at about 533K in an inert atmosphere of nitrogen for about 4–5 hours, the ring breaks and undergoes polymerization. Then the molten mass is passed through spinnerets to form fibres of nylon 6. Polymerization of caprolactam to Nylon 6. During polymerization, the amide bond within each caprolactam molecule is broken, with the active groups on each side re-forming two new bonds as the monomer becomes part of the polymer backbone.
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Phosphate affinity electrophoresis utilizes an affinity probe which consists of a molecule that binds specifically to divalent phosphate ions in neutral aqueous solution, known as a "Phos-Tag". This methods also utilizes a separation gel made of an acrylamide-pendent Phos-Tag monomer that is copolymerized. Phosphorylated proteins migrate slowly in the gel compared to non-phosphorylated proteins. This technique gives the researcher the ability to observe the differences in the phosphorylation states of any given protein.
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This compound was first prepared by treating uranium tetrafluoride with aluminium borohydride: : UF4 \+ 2 Al(BH4)3 → U(BH4)4 \+ 2 Al(BH4)F2 It may also be prepared by the solid-state reaction of uranium tetrachloride with lithium borohydride: :UCl4 \+ 4 LiBH4 → U(BH4)4 \+ 4 LiCl Although solid U(BH4)4 is a polymer, it undergoes cracking, converting to the monomer. The related methylborohydride complex U(BH3CH3)4 is monomeric as a solid and hence more volatile.
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Mesoporous manganese dioxide ambigels have been protected by 7-9 nm films of polymer such that dissolution of the manganese dioxide in aqueous acid was avoided. Uniform coatings require the architecture to be wetted by the monomer solution; this can be achieved through a solution that displays a similar surface energy to that of the porous solid. As the scale continuous to decrease and transport through the solid becomes more difficult, pre- equilibration is needed to ensure coating uniformity.
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500px One of the simplest and most thoroughly studied polymers arises from the polymerization of ethylene. Linear low-density polyethylene, LLDPE, is of industrial importance and is currently produced on the macro- scale; millions of tons per year. Branching of polyethylene involves the oligomerization of ethylene into alpha-olefins, carried out by one catalyst, followed by ethylene polymerization using the α-olefins as co- monomer, carried out by a second catalyst. This system suffers in practice.
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The idea to make mechanically strong polymeric materials by 1D supramolecular association of small molecules requires a high association constant between the repeating building blocks. In 1997, E.W. “Bert” Meijer reported a telechelic monomer with ureidopyrimidinone termini as a “self-complementary” quadruple hydrogen bonding motif and demonstrated that the resulting supramolecular polymer in chloroform shows a temperature-dependent viscoelastic property in solution. This is the first demonstration that supramolecular polymers, when sufficiently mechanically robust, are physically entangled in solution.
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This atypical feature of BglII suggests a unique hinge motion for DNA binding and release. Comparative structural studies of the free enzyme vs. the BglII-DNA complex showed that the enzyme opens by a dramatic scissor-like motion, accompanied by a complete rearrangement of the α-helices at the dimer interface. These structural studies also revealed that within each monomer a set of residues lowers or raises to alternatively sequester or expose the active site residues.
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This leads to repeated coupling of the nitroxide to the growing end of the polymer chain, which would ordinarily be considered a termination step, but is in this case reversible. Because of the high rate of coupling of the nitroxide to the growing chain end, there is little coupling of two active growing chains, which would be an irreversible terminating step limiting the chain length. The nitroxide binds and unbinds to the growing chain, protecting it from termination steps. This ensures that any available monomer can be easily scavenged by active chains. Because this polymerization process does not naturally self-terminate, this polymerization process is described as “living,” as the chains continue to grow under suitable reaction conditions whenever there is reactive monomer to “feed” them. Because of the PRE, it can be assumed that at any given time, almost all of the growing chains are “capped” by a mediating nitroxide, meaning that they dissociate and grow at very similar rates, creating a largely uniform chain length and structure.
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Surfactant protein A (SP-A) is a protein of 248 amino acids usually found in large oligomeric structures. The mature SP-A1 monomer is a 35kDa protein that differs from SP-A2 in four amino acids at the coding region. The structure of SP-A1 monomers consists of four domains: an N-terminal, a collagen-like domain, a neck region, and a carbohydrate recognition domain. The C-terminal carbohydrate recognition domain (CRD) allows binding to various types of microorganisms and molecules.
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The monomer are thus activated but the polymerization will not proceed significantly until the temperature is raised as part of the post expose bake. It is at this stage that the epoxy groups in the resin cross-link to form the cured structure. When fully cured the high crosslinking degree gives to the resist its excellent mechanical properties. The processing of SU-8 is similar to other negative resists with particular attention on the control of the temperature in the baking steps.
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Hosts (5–7) utilize hydrogen bonds and halogen bonds to hold monomer (2) at an optimal distance from each other to facilitate polymerization. In fact, when host 7 was used, polymerization occurred spontaneously upon isolation of the co-crystals. Crystal structures show the polymer strands are all parallel to the hydrogen- bonding network, and the host nitriles are each halogen-bonded to iodine atoms. Half of the iodine atoms in (1) in the crystal are in close contact to the oxalamide oxygen atoms.
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It is present in most cellular fibronectin, but only one of the two subunits in a plasma fibronectin dimer contains a V-region sequence. The modules are arranged into several functional and protein-binding domains along the length of a fibronectin monomer. There are four fibronectin-binding domains, allowing fibronectin to associate with other fibronectin molecules. One of these fibronectin-binding domains, I1–5, is referred to as the "assembly domain", and it is required for the initiation of fibronectin matrix assembly.
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Working model of Cobl-induced actin nucleation. Cobl is responsible for the actin polymerization of filaments with fast- growing barbed ends. Cobl stabilizes a longitudinal actin-GTP dimer by two consecutive WH2 domains and it can interact laterally with another actin monomer to form an actin trimer. Rearrangements of the actin–actin contacts have to occur within this trimer to make a helical nucleus; the third WH2 domain of Cobl has been proposed to interact with the third actin subunit of this trimer.
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With step-growth polymerization, the reaction can be terminated by adding a monofunctional species containing the same functionality as one or more of the types of monomer used in the reaction. For example, an alcohol R'-OH can be used to stop a reaction between a polyisocyanate and a polyol because it will react with the isocyanate functionality R-N=C=O to produce R-(N-H)-(C=O)-O-R' which is then no longer reactive with the polyol.
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The most distinguishable feature of sequence-controlled polymers is the well- ordered chains composed of different repeating units. By encoding the repeating units, the correspondingly synthesized sequence-controlled polymer can be used for data storage. To modify the monomer with some bioactive moieties, the obtained sequence-controlled polymer is able to treat diseases. The property of sequence control make sequence-controlled polymers an ideal platform to install various kinds of pendants (like drugs, catalyst), whereby diverse functions and applications can be realized.
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DNA-binding protein RFX2 is a protein that in humans is encoded by the RFX2 gene. This gene is a member of the regulatory factor X gene family, which encodes transcription factors that contain a highly-conserved winged helix DNA binding domain. The protein encoded by this gene is structurally related to regulatory factors X1, X3, X4, and X5. It is a transcriptional activator that can bind DNA as a monomer or as a heterodimer with other RFX family members.
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The biggest advantage of GFP is that it can be heritable, depending on how it was introduced, allowing for continued study of cells and tissues it is expressed in. Visualizing GFP is noninvasive, requiring only illumination with blue light. GFP alone does not interfere with biological processes, but when fused to proteins of interest, careful design of linkers is required to maintain the function of the protein of interest. Moreover, if used with a monomer it is able to diffuse readily throughout cells.
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Indeed, they can be viewed as a string of beads, with each bead representing a single nucleotide or amino acid monomer linked together through covalent chemical bonds into a very long chain. In most cases, the monomers within the chain have a strong propensity to interact with other amino acids or nucleotides. In DNA and RNA, this can take the form of Watson-Crick base pairs (G-C and A-T or A-U), although many more complicated interactions can and do occur.
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Zinc-finger nickases (ZFNickases) are created by inactivating the catalytic activity of one ZFN monomer in the ZFN dimer required for double-strand cleavage. ZFNickases demonstrate strand-specific nicking activity in vitro and thus provide for highly specific single-strand breaks in DNA. These SSBs undergo the same cellular mechanisms for DNA that ZFNs exploit, but they show a significantly reduced frequency of mutagenic NHEJ repairs at their target nicking site. This reduction provides a bias for HR-mediated gene modifications.
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Cyanobacteria photosystem II, Monomer, PDB 2AXT. Photosystem II is the photosystem that generates the two electrons that will eventually reduce NADP+ in ferredoxin-NADP-reductase. Photosystem II is present on the thylakoid membranes inside chloroplasts, the site of photosynthesis in green plants. The structure of photosystem II is remarkably similar to the bacterial reaction center, and it is theorized that they share a common ancestor. The core of photosystem II consists of two subunits referred to as D1 and D2.
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Front (top) and side (bottom) views of the structure (PDB: 1rzr) of CcpA (green and red) in complex with co-regulator Hpr-Ser46-P (blue) and target (operator) DNA sequence (gold). CcpA binds DNA as a homodimer (green and red monomer chains) in the N-terminal region of the protein. Binding is modulated allosterically by binding of Hpr-Ser46-P (blue) and small molecule ligands (not shown). Catabolite Control Protein A (CcpA) is a master regulator of carbon metabolism in gram-positive bacteria.
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Alkaline phosphatase (ALP, ALKP, ALPase, Alk Phos) (), or basic phosphatase, is a homodimeric protein enzyme of 86 kilodaltons. Each monomer contains five cysteine residues, two zinc atoms and one magnesium atom crucial to its catalytic function, and it is optimally active at alkaline pH environments. ALP has the physiological role of dephosphorylating compounds. The enzyme is found across a multitude of organisms, prokaryotes and eukaryotes alike, with the same general function but in different structural forms suitable to the environment they function in.
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2,6-Dimethylnaphthalene is mainly used for the preparation of 2,6-naphthalenedicarboxylic acid by oxidation of 2,6-dimethylnaphthalene in the liquid phase. 2,6-Naphthalenedicarboxylic acid is a monomer for the production of high-performance polymers, in particular poly (ethylene-2,6-naphthalene dicarboxylate) or shorter polyethylene naphthalate (PEN), a polyester which is stronger and has a higher thermal resistance than the frequently used polyethylene terephthalate (PET). However, 2,6-DMN is a more expensive intermediate than terephthalic acid that is used for PET.
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It must be high enough to allow for rearrangement and annealing of atoms during the synthesis process while being low enough to promote crystal growth. The concentration of monomers is another critical factor that has to be stringently controlled during nanocrystal growth. The growth process of nanocrystals can occur in two different regimes, "focusing" and "defocusing". At high monomer concentrations, the critical size (the size where nanocrystals neither grow nor shrink) is relatively small, resulting in growth of nearly all particles.
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As an example, the structure of C-phycocyanin from Synechococcus vulcanus has been refined to 1.6 Angstrom resolution. The (αβ) monomer consists of 332 amino acids and 3 thio-linked phycocyanobilin (PCB) cofactor molecules. Both the α- and β-subunits have a PCB at amino acid 84, but the β-subunit has an additional PCB at position 155 as well. This additional PCB faces the exterior of the trimeric ring and is therefore implicated in inter-rod energy transfer in the phycobilisome complex.
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The Catalytic Triad of CURS1-Created in PyMol using PDB: 3OV2, doi:10.1074/jbc.M110.196279 Crystallization studies have determined that curcumin synthase is a homodimer of ketosynthase subunits. Each includes a highly conserved Cys (164), His (303), Asn (336) catalytic triad, and CURS1 has been shown to exhibit the αβαβα folding pattern, conserved features of type III PKSs. The catalytic triads are independent of each other and are contained in the center of each monomer, connected to the surface with a CoA binding tunnel.
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Orc1/Cdc6 paralogs are two-domain proteins and are composed of a AAA+ ATPase module fused to a C-terminal winged-helix fold. DNA-complexed structures of Orc1/Cdc6 revealed that ORBs are bound by an Orc1/Cdc6 monomer despite the presence of inverted repeat sequences within ORB elements. Both the ATPase and winged- helix regions interact with the DNA duplex but contact the palindromic ORB repeat sequence asymmetrically, which orients Orc1/Cdc6 in a specific direction on the repeat.
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At first glance, the primary sequence of PA does not look like that of a membrane-spanning protein. A hydrophobicity plot lacking any patterns which are common to possible membrane-spanning domains. The structures of other multimeric membrane proteins (such as diphtheria toxin) provide the answer to how PA manages to span the membrane. It is thought that PA acts like these multimeric membrane proteins that form β-barrels made from stretches of both polar and non-polar amino acids from each monomer.
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Condensation polymerization is an important class of step-growth polymerization, which is formed simply by the reaction of two monomers and results in the release of a water molecule. Since these polymers are typically made up of two or more monomers, the resulting end groups are from the monomer functionality. Examples of condensation polymers can be seen with polyamides, polyacetals and polyesters. An example of polyester is polyethylene terephthalate (PET), which is made from the monomers terephthalic acid and ethylene glycol.
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A random coil is a polymer conformation where the monomer subunits are oriented randomly while still being bonded to adjacent units. It is not one specific shape, but a statistical distribution of shapes for all the chains in a population of macromolecules. The conformation's name is derived from the idea that, in the absence of specific, stabilizing interactions, a polymer backbone will "sample" all possible conformations randomly. Many linear, unbranched homopolymers — in solution, or above their melting temperatures — assume (approximate) random coils.
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Hadjichristidis N., Pispas S., Floudas G. Block copolymers: synthetic strategies, physical properties, and applications – Wiley, 2003. An emerging technique is chain shuttling polymerization. The synthesis of block copolymers requires that both reactivity ratios are much larger than unity (r1 >> 1, r2 >> 1) under the reaction conditions, so that the terminal monomer unit of a growing chain tends to add a similar unit most of the time. The "blockiness" of a copolymer is a measure of the adjacency of comonomers vs their statistical distribution.
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The paratope at the amino terminal end of the antibody monomer is shaped by the variable domains from the heavy and light chains. The variable domain is also referred to as the FV region and is the most important region for binding to antigens. To be specific, variable loops of β-strands, three each on the light (VL) and heavy (VH) chains are responsible for binding to the antigen. These loops are referred to as the complementarity-determining regions (CDRs).
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The synthetic route using lactams (cyclic amides) was developed by Paul Schlack at IG Farben, leading to nylon 6, or polycaprolactam — formed by a ring-opening polymerization. The peptide bond within the caprolactam is broken with the exposed active groups on each side being incorporated into two new bonds as the monomer becomes part of the polymer backbone. The 428 °F (220 °C) melting point of nylon 6 is lower than the 509 °F (265 °C) melting point of nylon 66.
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The copper amine oxidase 3-dimensional structure was determined through X-ray crystallography. The copper amine oxidases occur as mushroom-shaped homodimers of 70-95 kDa, each monomer containing a copper ion and a covalently bound redox cofactor, topaquinone (TPQ). TPQ is formed by post-translational modification of a conserved tyrosine residue. The copper ion is coordinated with three histidine residues and two water molecules in a distorted square pyramidal geometry, and has a dual function in catalysis and TPQ biogenesis.
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Attempts to produce more concentrated solutions result in the formation of silica gel. Because the concentration of orthosilicic acid in water is so low, the compounds that are present in solution have not been fully characterized. Linus Pauling predicted that silicic acid would be a very weak acid. :Si(OH)4 Si(OH)3O− \+ H+ The situation changed in 2017, when the orthosilicic acid monomer was obtained by hydrogenolysis of tetrakis(benzoyloxy)silane, (Si(OCH2C6H5)4, in solution in dimethylacetamide or related solvents.
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Cytoskeletal dynamics are key to issues like the appropriate spatial organization of subcellular material and cell shape changes. In the budding yeast Saccharomyces cerevisiae, actin filaments are the major structural component of the cytoskeleton. Profilin is an actin monomer binding protein that has been implicated in the control of actin polymerization and signal transduction; perhaps linking the two. With several of his students, he has been attempting to characterize the PTM1 gene and its protein product at the molecular and cellular level.
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The λ repressor of bacteriophage lambda employs two helix-turn-helix motifs (left; green) to bind DNA (right; blue and red). The λ repressor protein in this image is a dimer In proteins, the helix-turn-helix (HTH) is a major structural motif capable of binding DNA. Each monomer incorporates two α helices, joined by a short strand of amino acids, that bind to the major groove of DNA. The HTH motif occurs in many proteins that regulate gene expression.
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Profilin was first described by Lars Carlsson in the lab of Uno Lindberg and co-workers in the early 1970s as the first actin monomer binding protein. It followed the realization that not only muscle, but also non-muscle cells, contained high concentrations of actin, albeit in part in an unpolymerized form. Profilin was then believed to sequester actin monomers (keep them in a pro-filamentous form), and release them upon a signal to make them accessible for fast actin polymer growth.
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Despite the wide distribution, Heliorhodopsins are never present in true diderms, where there is a proper double membrane around the microorganism. It has been suggested that the function of Heliorhodopsin requires a direct interaction with the environment. Crystal structure of a monomer of heliorhodopsin from Thermoplasmatales archaeon SG8-52-1, based on . Crystal structures of Heliorhodopsins suggest they form a homodimer, contain a fenestration leading toward the retinal molecule and have a large extracellular loop facing the outside of the cell.
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Idealized EPDM polymer, red = ethylene-derived, blue = propylene-derived, black = ethylidene norbornene-derived. EPDM rubber (ethylene propylene diene monomer rubber) is a type of synthetic rubber that is used in many applications. EPDM is an M-Class rubber under ASTM standard D-1418; the M class comprises elastomers having a saturated chain of the polyethylene type (the M deriving from the more correct term polymethylene). EPDM is made from ethylene, propylene, and a diene comonomer that enables crosslinking via Sulfur vulcanization.
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The primary use of acetic acid is the production of vinyl acetate monomer (VAM). In 2008, this application was estimated to consume a third of the world's production of acetic acid. The reaction consists of ethylene and acetic acid with oxygen over a palladium catalyst, conducted in the gas phase. : 2 H3C−COOH + 2 C2H4 \+ O2 → 2 H3C−CO−O−CH=CH2 \+ 2 H2O Vinyl acetate can be polymerised to polyvinyl acetate or other polymers, which are components in paints and adhesives.
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The overall enzyme exists as a dimer-of-dimers: two identical subunits closely interact to form a dimer through salt bridges between arginine (R438 - exact positions may vary depending on the origin of the gene) and glutamic acid (E433) residues. This dimer assembles (more loosely) with another of its kind to form the four subunit complex. The monomer subunits are mainly composed of alpha helices (65%), and have a mass of 106kDa each. The sequence length is about 966 amino acids.
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The two-step synthesis scheme for a cardo polyimide Polyimides are polymers made up of imide group is incorporated into the monomers, with the imide existing in the backbone of the chain. These can be synthesized by either a one-step route or a two-step route. The two-step route involves first reacting the diamine monomer with an acid chloride or carboxylic acid to form a polygamic acid. Heating the polygamic acid then results in cyclodehydration, forming the imide.
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The protein, which is the functional equivalent of the E. coli L10 ribosomal protein, belongs to the L10P family of ribosomal proteins. It is a neutral phosphoprotein with a C-terminal end that is nearly identical to the C-terminal ends of the acidic ribosomal phosphoproteins P1 and P2. The P0 protein can interact with P1 and P2 to form a pentameric complex consisting of P1 and P2 dimers, and a P0 monomer. The protein is located in the cytoplasm.
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The protein encoded by this gene is structurally related to regulatory factors X2, X3, X4, and X5. It is a transcriptional activator that can bind DNA as a monomer or as a heterodimer with RFX family members X2, X3, and X5, but not with X4. This protein binds to the Xboxes of MHC class II genes and is essential for their expression. Also, it can bind to an inverted repeat that is required for expression of hepatitis B virus genes.
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While some studies support the idea of a hand-cuff model, the model is inconsistent with a number of experimental observations, and is generally considered to entrap chromatin as a monomer. Even though the ring hypothesis appears to be valid, there are still questions about the number of rings required to hold sister chromatids together. One possibility is that one ring surrounds the two chromatids. Another possibility involves the creation of a dimer where each ring surrounds one sister chromatid.
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Advantages of this polymer are optical transparency in its conducting state, high stability and moderate band gap and low redox potential. A large disadvantage is poor solubility, which is partly circumvented in the PEDOT:PSS composite, and the PEDOT-TMA material. Applications of PEDOT include electrochromic displays, antistatics, photovoltaics, electroluminescent displays, printed wiring, sensors, and potentially interfacing electronic hardware with human tissue. The polymer is generated by oxidation. This process begins with production of the radical cation of EDOT monomer, [C2H4O2C4H2S]+.
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Free radicals in solvent can potentially react with a monomer within the solvent cage or diffuse out. The cage effect in chemistry describes how the properties of a molecule are affected by its surroundings. First introduced by Franck and Rabinowitch in 1934, the cage effect suggests that instead of acting as an individual particle, molecules in solvent are more accurately described as an encapsulated particle. In order to interact with other molecules, the caged particle must diffuse from its solvent cage.
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However, in some we find a monomer ("which is more active and efficient [than its dimer counterpart"). The structure of ACS has been largely determined via X-ray crystallography. Conservation of the residues in ACS's catalytic domain and sequence homology suggest that ACS catalyzes the synthesis of ACC in a similar fashion as other enzymes that require PLP as a cofactor. However, unlike many other PLP- dependent enzymes, Lys (278) is not the only residue that interacts with the substrate.
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In mammals and yeast, a single enzyme performs both debranching functions. The human glycogen debranching enzyme (gene: AGL) is a monomer with a molecular weight of 175 kDa. It has been shown that the two catalytic actions of AGL can function independently of each other, demonstrating that multiple active sites are present. This idea has been reinforced with inhibitors of the active site, such as polyhydroxyamine, which were found to inhibit glucosidase activity while transferase activity was not measurably changed.
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BPA (Bisphenol A) is the monomer used to manufacture polycarbonate plastic and epoxy resins used as a lining in most food and beverage cans. BPA global capacity is in excess of per year and thus is one of the highest-volume chemicals produced worldwide. The ester bonds in the BPA-based polycarbonates could be subject to hydrolysis and leaching of BPA. But in the case of epoxypolymers formed from bisphenol A, it is not possible to release bisphenol A by such a reaction.
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The overall structure of TetR can be broken down into two DNA-binding domains (one per monomer) and a regulatory core, which is responsible for tetracycline recognition and dimerization. TetR dimerizes by making hydrophobic contacts within the regulatory core. There is a binding cavity for tetracycline in the outer helices of the regulatory domain. When tetracycline binds this cavity, it causes a conformational change that affects the DNA- binding domain so that TetR is no longer able to bind DNA.
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This can be utilized because hosts that are most commonly used are able to bond to the diyne monomer by halogen bonding from the lewis acidic iodine atom to a lewis basic nitrogen of the host (usually a nitrile or pyridine). In order to give a proper repeat distance to the monomers (5 Å), the hosts also contain oxalamide groups that create a hydrogen bonding network throughout the crystal. In most instances, polymerization is spontaneous upon crystallization or exposure to UV radiation/pressure.
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Dynamic instability is described as the switching of a polymer between phases of steady elongation and rapid shortening. This process is essential to the function of eukaryotic microtubules. In ParM, dynamic instability "rescue" or the switch from a shortening phase back to the elongation phase has very rarely been observed, and only when the ATP nucleotide is used. Unbound ParM filaments are found with a typical average length of 1.5 – 2 μm, when the ParM monomer concentrations are 2 μM or more.
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The plant was re-opened on 7 May 2020 following the nationwide lockdown implemented as a response to the COVID-19 pandemic. The plant stored 2,000 metric tons (1,968 long tons; 2,205 short tons) of styrene in tanks, which were left unattended. Styrene monomer must be stored between because higher temperatures result in rapid vaporization. It is believed that a computer glitch in the factory's cooling system allowed temperatures in the storage tanks to exceed safe levels, causing the styrene to vaporize.
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According to IUPAC, the functionality of a monomer is defined as the number of bonds that a monomer's repeating unit forms in a polymer with other monomers. Thus in the case of a functionality of f = 2 a linear polymer is formed by polymerizing (a thermoplastic). Monomers with a functionality f ≥ 3 lead to a branching point, which can lead to cross-linked polymers (a thermosetting polymer). Monofunctional monomers do not exist as such molecules lead to a chain termination.
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This protein was first isolated from the coelomic fluid in 1996 and named lysenin (from lysis and Eisenia). Lysenin is a relatively small water-soluble molecule with a molecular weight of 33 kDa. Using X-ray crystallography, lysenin was classified as a member of the Aerolysin protein family by structure and function. Structurally, each lysenin monomer consists of a receptor binding domain (grey globular part on right of Figure 1) and a Pore Forming Module (PFM); domains shared throughout the aerolysin family.
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HCN is the precursor to sodium cyanide and potassium cyanide, which are used mainly in gold and silver mining and for the electroplating of those metals. Via the intermediacy of cyanohydrins, a variety of useful organic compounds are prepared from HCN including the monomer methyl methacrylate, from acetone, the amino acid methionine, via the Strecker synthesis, and the chelating agents EDTA and NTA. Via the hydrocyanation process, HCN is added to butadiene to give adiponitrile, a precursor to Nylon-6,6.
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The CODH core is made up of two Ni- Fe-S clusters (C-cluster), two [FeS] clusters (B-cluster) and one [FeS] D-cluster. The D-cluster bridges the two subunits with one C and one B cluster in each monomer, allowing rapid electron transfer. The A-cluster of ACS is in constant communication with the C-cluster in CODH. This active site is also responsible for the C-C and C-S bond formations in the product acetyl-CoA (and its reverse reaction).
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The protein contains an extracellular V domain, a transmembrane domain, and a cytoplasmic tail. Alternate splice variants, encoding different isoforms, have been characterized. The membrane-bound isoform functions as a homodimer interconnected by a disulfide bond, while the soluble isoform functions as a monomer. The intracellular domain is similar to that of CD28, in that it has no intrinsic catalytic activity and contains one YVKM motif able to bind PI3K, PP2A and SHP-2 and one proline-rich motif able to bind SH3 containing proteins.
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This gene encodes a cytosolic enzyme that catalyzes the activation of acetate for use in lipid synthesis and energy generation. The protein acts as a monomer and produces acetyl-CoA from acetate in a reaction that requires ATP. It is also essential for the production of Crotonyl-CoA which activates its target genes by crotonylation of histone tails. Expression of this gene is regulated by sterol regulatory element-binding proteins, transcription factors that activate genes required for the synthesis of cholesterol and unsaturated fatty acids.
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A cutinase () is an enzyme that catalyzes the chemical reaction :cutin + H2O \rightleftharpoons cutin monomers Thus, the two substrates of this enzyme are cutin and H2O, whereas its product is cutin monomer. This enzyme belongs to the family of hydrolases, specifically those acting on carboxylic ester bonds. The systematic name of this enzyme class is cutin hydrolase. Aerial plant organs are protected by a cuticle composed of an insoluble polymeric structural compound, cutin, which is a polyester composed of hydroxy and hydroxyepoxy fatty acids.
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Odorant-binding protein 2a is a protein that in humans is encoded by the OBP2A gene. This gene encodes a small extracellular protein belonging to the lipocalin superfamily. The protein is thought to transport small, hydrophobic, volatile molecules or odorants through the nasal mucus to olfactory receptors, and may also function as a scavenger of highly concentrated or toxic odors. The protein is expressed as a monomer in the nasal mucus, and can bind diverse types of odorants with a higher affinity for aldehydes and fatty acids.
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Currently, it is mostly utilised in industrial processes that produce chlorine (mercury chlor-alkali plants) or vinyl chloride monomer for polyvinyl chloride (PVC) production, and polyurethane elastomers. It is extensively used to extract gold from ore in artisanal and small-scale gold mining. It is contained in products such as electrical switches (including thermostats), relays, measuring and control equipment, energy-efficient fluorescent light bulbs, batteries and dental amalgam. It is also used in laboratories, cosmetics, pharmaceuticals, including in vaccines as a preservative, paints, and jewellery.
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Aureo1a recognizes the sequence TGACGT, which is the typical binding site for certain subfamilies of bZIP transcription factors. It was also shown that PtAUREO1a and 1c are regulated in a light-independent circadian rhythm and that they are capable of forming homodimers and heterodimers which recognize the ACGT core sequence within the aureochrome. The photoreactions of AUREO 1 protein have been studied recently by Tsuguyoshi et al (2011) and they concluded that the AUREO1-LOV exists in equilibrium between the monomer and dimer. Huysman et al.
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So a pc of ½ means that the first point in time that an infinite network will be able to exist will be when ½ of all possible bonds have been made by the monomers. This equation is derived for the simple case of a self-reacting monomer with a single type of reacting group A. The Flory model was further refined by Stockmayer to include multifunctional monomers.Bowman, C. N.; Peppas, N. A. A kinetic gelation method for the simulation of free-radical polymerizations. Chemical Engineering Science.
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The transition probabilities are trained on databases of authentic classes of compounds. Also, the growth (and composition) of copolymers may be modeled using Markov chains. Based on the reactivity ratios of the monomers that make up the growing polymer chain, the chain's composition may be calculated (for example, whether monomers tend to add in alternating fashion or in long runs of the same monomer). Due to steric effects, second-order Markov effects may also play a role in the growth of some polymer chains.
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The AspAT-like small domain, the PLP-binding domain, and the carboxy-terminal domain form an open bowl-like structure. The wing domain extends from the other three domains like a handle of the bowl, and the linker domain connects these two parts together. Altogether, the five domains associate with one another through hydrogen bonds and electrostatic interactions. Arginine Decarboxylase Monomer showing: (A) Wing domain (purple); (B) linker domain (red); (C) PLP-binding-domain (orange); (D) AspAT-like small domain (blue); (E) carboxy-terminal domain (green).
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Each monomer comprises four distinct α/β structural units, each of which contains one of the four strands in each monomer's β-sheet and is made up only of the residues in a given sequence domain (see image at right). The burial of the active site (including Ser-116, the critical residue on the enzyme that is phosphorylated and dephosphorylated) in the hydrophobic interior of the enzyme serves to exclude water from counterproductively hydrolyzing critical phosphoester bonds while still allowing the substrate to access the active site.
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Cell casting is a method used for creating poly(methyl methacrylate) (PMMA) sheets. Liquid monomer is poured between two flat sheets of toughened glass sealed with a rubber gasket and heated for polymerization. Because the glass sheets may contain surface scratches or sag during the process, this traditional method has some disadvantages: among other problems, the PMMA sheets may contain variations in thickness and surface defects. It has since been replaced by the more modern method for making PMMA, extrusion, which gives uniform quality.
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In 1984, Shell opened both the Refinery and Chemical plant on the Scotford site. As one of North America's most modern and efficient refineries, the Scotford Refinery was the first to exclusively process synthetic crude oil from Alberta’s oil sands. Benzene that is produced during the refining process is sent to the adjacent Chemical plant and is used in the production of Styrene Monomer, a chemical needed to make many of the hard plastics people use daily. In 2000, a glycols plant was opened at Scotford Chemicals.
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7 α-Hemolysin monomers come together to create the mushroom-shaped pore. The 'cap' of the mushroom sits on the surface of the cell, and the 'stalk' of the mushroom penetrates the cell membrane, rendering it permeable (see later). The 'stalk' is composed of a 14-strand β-barrel, with two strands donated from each monomer. A structure of the Vibrio cholerae cytolysinPDB in the pore form is also heptameric; however, Staphylococcus aureus gamma-hemolysinPDB reveals an octomeric pore, consequently with a 16-strand 'stalk'.
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DNA Polymerase V (Pol V) is a polymerase enzyme involved in DNA repair mechanisms in prokaryotic bacteria, such as Escherichia coli. It is composed of a UmuD' homodimer and a UmuC monomer, forming the UmuD'2C protein complex. It is part of the Y-family of DNA Polymerases, which are capable of performing DNA translesion synthesis (TLS). Translesion polymerases bypass DNA damage lesions during DNA replication - if a lesion is not repaired or bypassed the replication fork can stall and lead to cell death.
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Two molecules of lactic acid can be dehydrated to lactide, a cyclic lactone. A variety of catalysts can polymerise lactide to either heterotactic or syndiotactic polylactide, which as biodegradable polyesters with valuable (inter alia) medical properties are currently attracting much attention. Nowadays, lactic acid is used as a monomer for producing polylactic acid (PLA) which later has application as biodegradable plastic. This kind of plastic is a good option for substituting conventional plastic produced from petroleum oil because of low emission of carbon dioxide.
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Ethoxylation is sometimes combined with propoxylation, the analogous reaction using propylene oxide as the monomer. Both reactions are normally performed in the same reactor and may be run simultaneously to give a random polymer, or in alternation to obtain block copolymers such as poloxamers. Propylene oxide is more hydrophobic than ethylene oxide and its inclusion at low levels can significantly affect the properties of the surfactant. In particular ethoxylated fatty alcohols which have been 'capped' with ~1 propylene oxide unit are extensively marketed as defoamers.
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PGK is found in all living organisms and its sequence has been highly conserved throughout evolution. The enzyme exists as a 415-residue monomer containing two nearly equal-sized domains that correspond to the N- and C-termini of the protein. 3-phosphoglycerate (3-PG) binds to the N-terminal, while the nucleotide substrates, MgATP or MgADP, bind to the C-terminal domain of the enzyme. This extended two-domain structure is associated with large-scale 'hinge-bending' conformational changes, similar to those found in hexokinase.
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TTR is a 55kDa homotetramer with a dimer of dimers quaternary structure that is synthesized in the liver, choroid plexus and retinal pigment epithelium for secretion into the bloodstream, cerebrospinal fluid and the eye, respectively. Each monomer is a 127-residue polypeptide rich in beta sheet structure. Association of two monomers via their edge beta-strands forms an extended beta sandwich. Further association of two of these dimers in a face-to-face fashion produces the homotetrameric structure and creates the two thyroxine binding sites per tetramer.
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The basic building block (monomer) of polyethylene is ethylene. Ethylene is chemically similar to, and can be derived from ethanol, which can be produced by fermentation of agricultural feedstocks such as sugar cane or corn. Bio- derived polyethylene is chemically and physically identical to traditional polyethylene – it does not biodegrade but can be recycled. The Brazilian chemicals group Braskem claims that using its method of producing polyethylene from sugar cane ethanol captures (removes from the environment) 2.15 tonnes of per tonne of Green Polyethylene produced.
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The DNA-binding functional unit of CcpA consists of a homodimer. The N-terminal region of each monomer form a DNA-binding site while the C-terminal portion forms a "regulatory" domain. A short linker connects the N-terminal DNA binding domain and the C-terminal regulatory domain, which partially contacts DNA when bound. The LacI/GalR subfamily can be functionally subdivided based on the presence or absence of a "YxxPxxxAxxL" motif in the liker sequence; CcpA belongs to the subdivision containing this motif.
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A review of DNA polymerase fidelity cites bis-tris propane as a suitable buffer for polymerase chain reaction (PCR). Bis-Tris propane has also been used with HCl buffer for stabilization of farnesyl diphosphate isolated from a strain of Saccharomyces cerevisiae. It has also been used in a study of the effects of buffer identity on electric signals of light-excited bacteriorhodospin. Use of Bis-Tris propane has also been documented in an investigation of the MgATPase activity of the myosin subfragment 1 monomer.
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In the capillaries, where oxygen concentration levels are lower, the T state is favored, in order to facilitate the delivery of oxygen to the tissues. The Bohr effect is dependent on this allostery, as increases in CO2 and H+ help stabilize the T state and ensure greater oxygen delivery to muscles during periods of elevated cellular respiration. This is evidenced by the fact that myoglobin, a monomer with no allostery, does not exhibit the Bohr effect. Haemoglobin mutants with weaker allostery may exhibit a reduced Bohr effect.
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It was produced industrially from paraformaldehyde and a mixture of chlorosulfonic acid and sulfuric acid.Wilhelm Heitmann, Günther Strehlke, Dieter Mayer “Ethers, Aliphatic” Ullmann's Encyclopedia of Industrial Chemistry 2002, Wiley-VCH, Weinheim. It is also produced as a byproduct in the Blanc chloromethylation reaction, formed when formaldehyde (the monomer, paraformaldehyde or formalin) and concentrated hydrochloric acid are mixed, and is a known impurity in technical grade chloromethyl methyl ether. Because of their carcinogenic potency, the industrial production of chloromethyl ethers ended in most countries in the early 1980s.
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In the ECW model, a new term W was added to the equation. : −ΔH = EAEB \+ CACB \+ W The W term represents a constant energy for cleavage of a dimeric acid or base. For example the enthalpy of cleavage the [Rh(CO)2Cl]2 by base B involves two steps. The first step is cleavage of the dimer, which is W: : ½ [Rh(CO)2Cl]2 → Rh(CO)2Cl W = -10.39 kcal/mol The second step is the binding of B to RhCl(CO)2 monomer.
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When seco acid is added into the system little by little using a syringe driver, all of the reactant is quickly converted into MA; then, the MA is immediately consumed by the cyclization reaction. As just described, MA concentration is kept low throughout the Shiina macrolactonization reaction. Therefore, the monomer production rate is very high. Aromatic carboxylic acid anhydrides are used as dehydration condensation agents not only for the intramolecular reaction of hydroxycarboxylic acids but also for the intermolecular reaction of carboxylic acids with alcohols (Shiina esterification).
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IRK channels possess a pore domain, homologous to that of voltage-gated ion channels, and flanking transmembrane segments (TMSs). They may exist in the membrane as homo- or heterooligomers and each monomer possesses between 2 and 4 TMSs. In terms of function, these proteins transport potassium (K+), with a greater tendency for K+ uptake than K+ export. The process of inward-rectification was discovered by Denis Noble in cardiac muscle cells in 1960s and by Richard Adrian and Alan Hodgkin in 1970 in skeletal muscle cells.
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The enzymes exist as homodimers. In eukaryotes, each monomer consisting of two major regions: an N-terminal oxygenase domain, which belongs to the class of heme-thiolate proteins, and a multi-domain C-terminal reductase, which is homologous to NADPH:cytochrome P450 reductase () and other flavoproteins. The FMN binding domain is homologous to flavodoxins, and the two domain fragment containing the FAD and NADPH binding sites is homologous to flavodoxin-NADPH reductases. The interdomain linker between the oxygenase and reductase domains contains a calmodulin-binding sequence.
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Production of novel MIPs has implicit challenges unique to this field. These challenges arise chiefly from the fact that all substrates are different and thus require different monomer and cross-linker combinations to adequately form imprinted polymers for that substrate. The first, and lesser, challenge arises from choosing those monomers which will yield adequate binding sites complementary to the functional groups of the substrate molecule. For example, it would be unwise to choose completely hydrophobic monomers to be imprinted with a highly hydrophilic substrate.
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These considerations need to be taken into account before any new MIP is created. Molecular modelling can be used to predict favourable interactions between templates and monomers, allowing intelligent monomer selection. Secondly, and more troublesome, the yield of properly created MIPs is limited by the capacity to effectively wash the substrate from the MIP once the polymer has been formed around it. In creating new MIPs, a compromise must be created between full removal of the original template and damaging of the substrate binding cavity.
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No cofactors are needed for catalysis. Additionally, the formation of riboflavin from 6,7-dimethyl-8-ribityllumazine can occur in boiling aqueous solution in the absence riboflavin synthase. At the interface of the substrate between monomer pairs, the enzyme holds the two 6,7-dimethyl-8-ribityllumazine molecules in position via hydrogen bonding to catalyze the dismutation reaction. Additionally, acid/base catalysis by the amino acid residues has been suggested. Specific residues may include the His102/Thr148 dyad as a base for deprotonation of the C7a methyl group.
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Each HSF monomer contains one C-terminal and three N-terminal leucine zipper repeats. Point mutations in these regions result in disruption of cellular localisation, rendering the protein constitutively nuclear in humans. Two sequences flanking the N-terminal zippers fit the consensus of a bi-partite nuclear localization signal (NLS). Interaction between the N- and C-terminal zippers may result in a structure that masks the NLS sequences: following activation of HSF, these may then be unmasked, resulting in relocalisation of the protein to the nucleus.
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CHEN, Polymer Aluminum Electrolytic Capacitors with Chemically-Polymerized Polypyrrole (PPy) as Cathode Materials Part I. Effect of Monomer Concentration and Oxidant on Electrical Properties of the Capacitors, PDF or PEDOTU. Merker, K. Wussow, W. Lövenich, H. C. Starck GmbH, New Conducting Polymer Dispersions for Solid Electrolyte Capacitors, ecadigitallibrary.com is better than that of TCNQ by a factor of 100 to 500, and close to the conductivity of metals. In 1991 Panasonic came on the market with its "SP-Cap", called polymer aluminum electrolytic capacitors.
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This equation is derived using the Markov model, which only considers the last segment added as affecting the kinetics of the next addition; the Penultimate Model considers the second-to-last segment as well, but is more complicated than is required for most systems. When both reactivity ratios are less than one, there is an azeotropic point in the Mayo-Lewis plot. At this point, the mole fraction of monomer equals the composition of the component in the polymer. There are several ways to synthesize random copolymers.
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In triglycerides, the main group of bulk lipids, there is one molecule of glycerol and three fatty acids. Fatty acids are considered the monomer in that case, and may be saturated (no double bonds in the carbon chain) or unsaturated (one or more double bonds in the carbon chain). Most lipids have some polar character in addition to being largely nonpolar. In general, the bulk of their structure is nonpolar or hydrophobic ("water- fearing"), meaning that it does not interact well with polar solvents like water.
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Interleukin 3 (IL3) is a cytokine that regulates hematopoiesis by controlling the production, differentiation and function of granulocytes and macrophages. The protein, which exists in vivo as a monomer, is produced in activated T cells and mast cells, and is activated by the cleavage of an N-terminal signal sequence. IL3 is produced by T lymphocytes and T-cell lymphomas only after stimulation with antigens, mitogens, or chemical activators such as phorbol esters. However, IL3 is constitutively expressed in the myelomonocytic leukaemia cell line WEHI-3B.
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Isosorbide is a bicyclic chemical compound from the group of diols and the oxygen-containing heterocycles, containing two fused furan rings. The starting material for isosorbide is D-sorbitol, which is obtained by catalytic hydrogenation of D-glucose, which is in turn produced by hydrolysis of starch. Isosorbide is discussed as a plant-based platform chemical from which biodegradable derivatives of various functionality can be obtained. Isosorbide is currently of great scientific and technical interest as a monomer building block for biopolymeric polycarbonates, polyesters, polyurethanes and epoxides.
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The process takes place without termination and transfer of the polymer chain with a degree of polymerization equal to the mole ratio of the monomer to the initiator.Berman, E.L., Gorkovenko, A.A., Rogozhkina, E.D., Izumnikov, A.A., and Ponomarenko, V.A. “Kinetics and Mechanism of Epoxy Ring- Opening Polymerization of 1,6;2,3-Dianhydro-4-O-alkyl-b-D-mannopyranoses” Polymer Sci. USSR, 1988, 413-418Berman E.L. Gorkovenko, A.A., Rogozhkina, E.D., Izyumnikov, A.L., and Ponomarenko, V.A. "Synthesis of Chiral Derivatives of Poly(Ethylene Oxide)" Bull. Acad. Sci. USSR, Div. Chem. Sci.
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Films can be formed on the order of 20 nm. Electrochemical polymerization (electrochemical deposition) is performed using a three-electrode configuration in a solution of the monomer of the desired polymer, a solvent, and an electrolyte (dopant). In the case of depositing a polymer coating onto electrode a common dopant used is poly (styrene sulfonate) or PSS because of its stability and biocompatibility. Two common conductive polymers being investigated for coatings use PSS as a dopant to be electrochemically deposited onto the electrode surface (see sections below).
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The first confirmed CCR was isolated from soybean (Glycine max) in 1976. However, crystal structures have so far been reported for just three CCR homologs: Petunia x hybrida CCR1, Medicago truncatula CCR2, and Sorghum bicolor CCR1. While the enzyme crystallizes as an asymmetric dimer, it is thought to exist as a monomer in the cytoplasm, with each individual protein having a bilobal structure consisting of two domains surrounding a large, empty inner cleft for substrate binding. Typical CCRs have a molecular weight of around 36-38 kDa.
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The general mechanism for anionic ring-opening polymerization. Polarized functional group is represented by X-Y, where the atom X (usually a carbon atom) becomes electron deficient due to the highly electron-withdrawing nature of Y (usually an oxygen, nitrogen, sulfur, etc.). The nucleophile will attack atom X, thus releasing Y-. The newly formed nucleophile will then attack the atom X in another monomer molecule, and the sequence would repeat until the polymer is formed. Anionic ring-opening polymerizations (AROP) are involve nucleophilic reagents as initiators.
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The Flory–Huggins solution theory provides the entropy of mixing for polymer solutions, in which the macromolecules are huge compared to the solvent molecules. In this case, the assumption is made that each monomer subunit in the polymer chain occupies a lattice site. Note that solids in contact with each other also slowly interdiffuse, and solid mixtures of two or more components may be made at will (alloys, semiconductors, etc.). Again, the same equations for the entropy of mixing apply, but only for homogeneous, uniform phases.
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The typical example are polyesters, polyamides and polyethers. It is sometimes confused by condensation previous definition of condensation polymerization. Polyaddition is a type of step-growth polymerization of which chain growth is based on addition reaction between two molecules of various degree of polymerization. The typical example for polyaddition is the synthesis of polyurethane. Compared to chain-growth polymerization, where the production of the growing chaingrowth is based on the reaction between polymer with active center and monomer, step-growth polymerization doesn’t have initiator or termination.
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Five common types of interfacial polymerization interfaces (from left to right): liquid-solid, liquid-liquid, and liquid-in-liquid emulsion. There are two examples each for liquid-liquid and liquid-in-liquid emulsion, either using one monomer or two. The most commonly used interfacial polymerization methods fall into 3 broad types of interfaces: liquid-solid interfaces, liquid-liquid interfaces, and liquid-in-liquid emulsion interfaces. In the liquid-liquid and liquid-in-liquid emulsion interfaces, either one or both liquid phases may contain monomers.
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This property allows FcγRI to bind a sole IgG molecule (or monomer), but all Fcγ receptors must bind multiple IgG molecules within an immune complex to be activated. The Fc-gamma receptors differ in their affinity for IgG and likewise the different IgG subclasses have unique affinities for each of the Fc gamma receptors. These interactions are further tuned by the glycan (oligosaccharide) at position CH2-84.4 of IgG. For example, by creating steric hindrance, fucose containing CH2-84.4 glycans reduce IgG affinity for FcγRIIIA.
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As of September 2017, there are 171 structures deposited in the Protein Data Bank. See this link for a complete list. The N and C termini of the 159 residue full-length protein are processed to give a shorter ‘core’ streptavidin, usually composed of residues 13–139; removal of the N and C termini is necessary for the highest biotin-binding affinity. The secondary structure of a streptavidin monomer is composed of eight antiparallel β-strands, which fold to give an antiparallel β-barrel tertiary structure.
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Alpha-actinin 2 is a 103.8 kDa protein composed of 894 amino acids. Each molecule is rod-shaped (35 nm in length) and it homodimerizes in an anti-parallel fashion. Each monomer has an N-terminal actin-binding region composed of two calponin homology domains, two C-terminal EF hand domains, and four tandem spectrin-like repeats form the rod domain in the central region of the molecule. The high-resolution crystal structure of human alpha-actinin 2 at 3.5 Å was recently resolved.
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SEM-Picture of PMMA-particles fabricated by dispersion polymerization after drying / removal of the organic liquid phase (cyclohexane) At the onset of polymerization, polymers remain in solution until they reach a critical molecular weight (MW), at which point they precipitate. These initial polymer particles are unstable and coagulate with other particles until stabilized particles form. After this point in the polymerization, growth only occurs by addition of monomer to the stabilized particles. As the polymer particles grow, stabilizer (or dispersant) molecules attach covalently to the surface.
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The most common route to PLA is the ring-opening polymerization of lactide with various metal catalysts (typically tin octoate) in solution or as a suspension. The metal-catalyzed reaction tends to cause racemization of the PLA, reducing its stereoregularity compared to the starting material (usually corn starch). The direct condensation of lactic acid monomers can also be used to produce PLA. This process needs to be carried out at less than 200 °C; above that temperature, the entropically favored lactide monomer is generated.
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The list of synthetic polymers, roughly in order of worldwide demand, includes polyethylene, polypropylene, polystyrene, polyvinyl chloride, synthetic rubber, phenol formaldehyde resin (or Bakelite), neoprene, nylon, polyacrylonitrile, PVB, silicone, and many more. More than 330 million tons of these polymers are made every year (2015).World Plastics Production Most commonly, the continuously linked backbone of a polymer used for the preparation of plastics consists mainly of carbon atoms. A simple example is polyethylene ('polythene' in British English), whose repeating unit is based on ethylene monomer.
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The distinguishing feature of PDE1 as a family is their regulation by calcium (Ca2+) and calmodulin (CaM). Calmodulin has been shown to activate cyclic nucleotide PDE in a calcium-dependent manner and the cooperative binding of four Ca2+ to calmodulin is required to fully activate PDE1 [2]. The binding of one Ca2+/CaM complex per monomer to binding sites near the N-terminus stimulates hydrolysis of cyclic nucleotides. In intact cells, PDE1 is almost exclusively activated by Ca2+ entering the cell from the extracellular space.
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Aminopeptidases play a role in the metabolism of several peptides that may be involved in blood pressure and the pathogenesis of essential hypertension. Mutations in the ARTS-1 have been linked to an increased risk of ankylosing spondylitis but only in HLA-B27 positive patients. The protein encoded by this gene is an aminopeptidase involved in trimming HLA class I-binding precursors so that they can be presented on MHC class I molecules. The encoded protein acts as a monomer or as a heterodimer with ERAP2.
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Even though PTPmu dimers may be active, an additional study suggests that the extracellular domain of PTPmu reduces phosphatase activity. In this study, it was shown that the cytoplasmic domain of PTPmu (a PTPmu molecule lacking the extracellular domain) has greater phosphatase activity than the full-length protein in an enzymatic phosphatase assay. PTPmu has a long juxtamembrane domain, which likely influences catalytic activity. The juxtamembrane domain of PTPmu can bind to either the D1 and/or D2 of PTPmu, but only within the same PTPmu monomer.
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7) from Listeria monocytogenes exhibits a proline rich sequence at its amino terminus that plays a role in the stability of LLO. The extreme case is lectinolysin (LLY; UniProt: B3UZR3) from some strains of Streptococcus mitis and S. pseudopneumoniae contain a functional fucose-binding lectin at the amino terminus. Furthermore, all CDCs contain a highly conserved undecapeptide, which is thought to be critical for cholesterol-mediated membrane recognition. The CDC monomer consist of 4 structural domains, with domain 4 (D4) being involved with membrane binding.
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Ethylene vinyl alcohol (EVOH) is a formal copolymer of ethylene and vinyl alcohol. Because the latter monomer mainly exists as its tautomer acetaldehyde, the copolymer is prepared by polymerization of ethylene and vinyl acetate to give the ethylene vinyl acetate (EVA) copolymer followed by hydrolysis. EVOH copolymer is defined by the mole % ethylene content: lower ethylene content grades have higher barrier properties; higher ethylene content grades have lower temperatures for extrusion. The plastic resin is commonly used as an oxygen barrier in food packaging.
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Glycerol dehydrogenase is a homooctamer composed of eight identical monomer subunits made up of a single polypeptide chain of 370 amino acids (molecular weight 42,000 Da). Each subunit contains 9 beta sheets and 14 alpha helices within two distinct domains (N-terminal, residues 1-162 and C-terminal, residues 163-370). The deep cleft formed between these two domains serves as the enzyme’s active site. This active site consists of one bound metal ion, one NAD+ nicotinamide ring binding site, and a substrate binding site.
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Hydrophobic monomers are emulsified through an aqueous phase. Free radicals are created in order to produce the polymer with either water or oil soluble initiators. Inverse suspension polymerization is carried out by using an aqueous solution of the monomer, cross-linking agent, and initiator which is then added to an organic phase which is stabilized by a surfactant. Plasma polymerization utilizes a range of technologies such as electron beams, ultraviolet radiation, or glow discharge in order to form polymers from a vapor made out of monomers.
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ATRP reactions are very robust in that they are tolerant of many functional groups like allyl, amino, epoxy, hydroxy, and vinyl groups present in either the monomer or the initiator.Cowie, J. M. G.; Arrighi, V. In Polymers: Chemistry and Physics of Modern Materials; CRC Press Taylor and Francis Group: Boca Raton, Fl, 2008; 3rd Ed., pp. 82–84 ATRP methods are also advantageous due to the ease of preparation, commercially available and inexpensive catalysts (copper complexes), pyridine-based ligands, and initiators (alkyl halides). The ATRP with styrene.
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There are several theoretical definitions of CMC. One well-known definition is that CMC is the total concentration of surfactants under the conditions:Phillips J. The energetics of micelle formation. Transactions of the Faraday Society 1955;51:561-9 :if C = CMC, (d3F/dCt3) = 0 :F = a[micelle] + b[monomer]: function of surfactant solution :Ct: total concentration :a, b: proportional constants The CMC generally depends on the method of measuring the samples, since a and b depend on the properties of the solution such as conductance and photochemical characteristics.
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As a reactive monomer, ethyl acrylate is used in homopolymers and copolymers with e.g. ethene, acrylic acid and its salts, amides and esters, methacrylates, acrylonitrile, maleic esters, vinyl acetate, vinyl chloride, vinylidene chloride, styrene, butadiene and unsaturated polyesters. Copolymers of acrylic acid ethyl ester with ethene (EPA/ethylene-ethyl acrylate copolymers) are suitable as adhesives and polymer additives, just like ethene vinyl acetate copolymers. Copolymers with acrylic acid increase the cleaning effect of liquid detergents, copolymers with methacrylic acid are used as gastric juices tablet covers (Eudragit).
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The (2R,3R)-stereoisomer of 2,3-butanediol is produced by a variety of microorganisms in a process known as butanediol fermentation. It is found naturally in cocoa butter, in the roots of Ruta graveolens, sweet corn, and in rotten mussels. It is used in the resolution of carbonyl compounds in gas chromatography. During World War II research was done towards producing 2,3-butanediol by fermentation in order to produce 1,3-butadiene, the monomer of the polybutadiene used in a leading type of synthetic rubber.
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Insulin in some invertebrates is quite similar in sequence to human insulin, and has similar physiological effects. The strong homology seen in the insulin sequence of diverse species suggests that it has been conserved across much of animal evolutionary history. The C-peptide of proinsulin, however, differs much more among species; it is also a hormone, but a secondary one. Insulin is produced and stored in the body as a hexamer (a unit of six insulin molecules), while the active form is the monomer.
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Each monomer in the complex has a substrate binding site that binds to G6P, and a catalytic coenzyme binding site that binds to NADP+/NADPH using the Rossman fold. For some higher organisms, such as humans, G6PD contains an additional NADP+ binding site, called the NADP+ structural site, that does not seem to participate directly in the reaction catalyzed by G6PD. The evolutionary purpose of the NADP+ structural site is unknown. As for size, each monomer is approximately 500 amino acids long (514 amino acids for humans). Functional and structural conservation between human G6PD and Leuconostoc mesenteroides G6PD points to 3 widely conserved regions on the enzyme: a 9 residue peptide in the substrate binding site, RIDHYLGKE (residues 198-206 on human G6PD), a nucleotide-binding fingerprint, GxxGDLA (residues 38-44 on human G6PD), and a partially conserved sequence EKPxG near the substrate binding site (residues 170-174 on human G6PD), where we have use "x" to denote a variable amino acid. The crystal structure of G6PD reveals an extensive network of electrostatic interactions and hydrogen bonding involving G6P, 3 water molecules, 3 lysines, 1 arginine, 2 histidines, 2 glutamic acids, and other polar amino acids.
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William Martin and Michael Russell suggest that the first cellular life forms may have evolved inside alkaline hydrothermal vents at seafloor spreading zones in the deep sea. These structures consist of microscale caverns that are coated by thin membraneous metal sulfide walls. Therefore, these structures would resolve several critical points germane to Wächtershäuser's suggestions at once: # the micro-caverns provide a means of concentrating newly synthesised molecules, thereby increasing the chance of forming oligomers; # the steep temperature gradients inside the hydrothermal vent allow for establishing "optimum zones" of partial reactions in different regions of the vent (e.g. monomer synthesis in the hotter, oligomerisation in the cooler parts); # the flow of hydrothermal water through the structure provides a constant source of building blocks and energy (chemical disequilibrium between hydrothermal hydrogen and marine carbon dioxide); # the model allows for a succession of different steps of cellular evolution (prebiotic chemistry, monomer and oligomer synthesis, peptide and protein synthesis, RNA world, ribonucleoprotein assembly and DNA world) in a single structure, facilitating exchange between all developmental stages; # synthesis of lipids as a means of "closing" the cells against the environment is not necessary, until basically all cellular functions are developed.
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The overall phosphorylation of thymidine to thymidine triphosphate does not follow Michaelis-Menten kinetics, and the various phosphates of thymidine and uridine interfere with the phosphorylation of each other. The kinetics of TK from different species differ from each other's and also the different forms from a given species (monomer, dimer, tetramer and serum form) have different kinetic characteristics. Genes for virus specific thymidine kinases have been identified in Herpes simplex virus, Varicella zoster virus and Epstein-Barr virus. 120px + ATP ---> 200px + ADP Thymidine reacts with ATP to give thymidine monophosphate and ADP.
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Polyacetylene can be synthesized by ring-opening metathesis polymerization (ROMP) from cyclooctatetraene, a material easier to handle than the acetylene monomer. This synthetic route also provides a facile method for adding solubilizing groups to the polymer while maintaining the conjugation. Robert Grubbs and coworkers synthesized a variety of polyacetylene derivatives with linear and branched alkyl chains. Polymers with linear groups such as n-octyl had high conductivity but low solubility, while highly branched tert- butyl groups increased solubility but decreased conjugation due to polymer twisting to avoid steric crowding.
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It is suspected that within solid titanium(IV) hydride, the molecules form aggregations (polymers), being connected by covalent bonds. Calculations suggest that TiH4 is prone to dimerisation. This largely attributed to the electron deficiency of the monomer and the small size of the hydride ligands; which allows dimerisation to take place with a very low energy barrier as there is a negligible increase in inter-ligand repulsion. The dimer is a calculated to be a fluxional molecule rapidly inter-converting between a number of forms, all of which display bridging hydrogens.
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Interfacial cross-linking is derived from interfacial polycondensation, and was developed to avoid the use of toxic diamines, for pharmaceutical or cosmetic applications. In this method, the small bifunctional monomer containing active hydrogen atoms is replaced by a biosourced polymer, like a protein. When the reaction is performed at the interface of an emulsion, the acid chloride reacts with the various functional groups of the protein, leading to the formation of a membrane. The method is very versatile, and the properties of the microcapsules (size, porosity, degradability, mechanical resistance) can be customized.
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By late 1961 he succeeded in producing the first four hydrogel contact lenses on a home-made apparatus built using a children's building kit (Merkur) and a bicycle dynamo belonging to one of his sons, and a bell transformer. All the moulds and glass tubing needed to dose them with monomer were also individually made by himself. On Christmas afternoon, with the help of his wife Linda, using the machine on his kitchen table, he finally succeeded. He tried the lenses in his own eyes and although they were the wrong power they were comfortable.
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Other tubes containing a hardening agent also crack and mix with the monomer, causing the crack to be healed. There are many things to take into account when introducing hollow tubes into a crystalline structure. First to consider is that the created channels may compromise the load bearing ability of the material due to the removal of load bearing material. Also, the channel diameter, degree of branching, location of branch points, and channel orientation are some of the main things to consider when building up microchannels within a material.
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Recent progress has been made for (partially) ionized MAA by introducing a new rate law for propagation where electrostatic and non- electrostatic effects are explicitly considered. In addition, the rate constant of propagation (kp) during free radical polymerization of methacrylic acid is prone to the monomer concentration. With pulsed layer polymerization size-exclusion chromatography techniques, it was determined that there is a minor decrease for partially ionized MAA while when MAA is fully ionized, kp increases with higher concentration. The latter is in accordance with transition state theory for propagation.
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The protein encoded by this gene is a serine/threonine protein kinase and a member of the casein kinase I protein family, whose members have been implicated in the control of cytoplasmic and nuclear processes, including DNA replication and repair. The encoded protein is found in the cytoplasm as a monomer and can phosphorylate a variety of proteins, including itself. This protein has been shown to phosphorylate proteins of the Period family of circadian rhythm proteins. A homolog of this mammalian protein can be found in Drosophila melanogaster.
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UCH-L1 is a member of a gene family whose products hydrolyze small C-terminal adducts of ubiquitin to generate the ubiquitin monomer. Expression of UCH-L1 is highly specific to neurons and to cells of the diffuse neuroendocrine system and their tumors. It is abundantly present in all neurons (accounts for 1-2% of total brain protein), expressed specifically in neurons and testis/ovary. The catalytic triad of UCH-L1 contains a cysteine at position 90, an aspartate at position 176, and a histidine at position 161 that are responsible for its hydrolase activity.
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In molecular biology, the Cfr10I/Bse634I family of restriction endonucleases includes the type II restriction endonucleases Cfr10I and Bse634I. They exhibit a conserved tetrameric architecture that is of functional importance, wherein two dimers are arranged, back-to-back, with their putative DNA-binding clefts facing opposite directions. These clefts are formed between two monomers that interact, mainly via hydrophobic interactions supported by a few hydrogen bonds, to form a U-shaped dimer. Each monomer is folded to form a compact alpha-beta structure, whose core is made up of a five-stranded mixed beta-sheet.
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Class I monolayer contains the same core structure as amyloid fibrils, and is positive to Congo red and thioflavin T. The monolayer formed by class I hydrophobins has a highly ordered structure, and can only be dissociated by concentrated trifluoroacetate or formic acid. Monolayer assembly involves large structural rearrangements with respect to the monomer. Fungi make complex aerial structures and spores even in aqueous environments. Hydrophobins have been identified in lichens as well as non-lichenized ascomycetes and basidiomycetes; whether they exist in other groups is not known.
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YadA is an example of an oligomeric coiled-coil adhesin (Oca). The Oca protein families are a subset of autotransporters, also known as the type Vc or trimeric autotransporters. Trimerization is thought to involve the coiled-coil stem and the C-terminal membrane anchor, which forms a 12-strand beta-barrelfrom the four transmembrane beta-strands of the three monomers. This beta-barrel would form a pore-like structure through which the N-terminal head and coiled helical domains of the three monomer chains exit to the cell surface.
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Keratin (high molecular weight) in bile duct cell and oval cells of horse liver. Fibrous keratin molecules supercoil to form a very stable, left-handed superhelical motif to multimerise, forming filaments consisting of multiple copies of the keratin monomer. The major force that keeps the coiled-coil structure is hydrophobic interactions between apolar residues along the keratins helical segments. Limited interior space is the reason why the triple helix of the (unrelated) structural protein collagen, found in skin, cartilage and bone, likewise has a high percentage of glycine.
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Ara h 1 is a vicilin, located in the protein fraction of the peanut cotyledon. Ara h 1 forms homotrimers, and due to its highly stable structure, mediated through hydrophobic interactions, it has been established as an allergen. Hydrophobic residues on α-helical bundles are located on the ends of each trimer monomer. Ara h 1 presents an overall pleat like bicupins, N- and C-terminal domains are superposed in 1.9 Å. The molecule has two modules related by an axis perpendicular to the three pleat axes of the trimer.
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The active bifunctional enzyme of trypanothione synthase is found as a 74.4 KDa monomer consisting of 652 residues with two catalytic domains. Its C-terminal domain is a synthetase and has an ATP-grasp family fold that is usually found in carbon-nitrogen ligases. The N-terminal domain is a cysteine, histidine-dependent aminohydrolase amidase. Structurally the synthetase and amidase domains are bound together by three residues of Glu-650-Asp-651-Glu-652 through hydrogen bonding and salt bridge interactions with basic side chains in order for the protein to properly fold.
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Representation of the molecular structure of protein RepA, a known rep protein used in iterons The replication initiator protein (Rep) plays a key role in initiation of replication in plasmids. In its monomer form, Rep binds an iteron and promotes replication. The protein itself is known to contain two independent N-terminal and C-terminal globular domains that subsequently bind to two domains of the iteron. The dimer version of the protein is generally inactive in iteron binding, however it is known to bind to the repE operator.
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A. Detailed interactions of MRJP1 and apisimin in the MRJP1 dimer; symmetric intermolecular C-terminal and N-terminal interactions and intermolecular C-terminal antiparallel β-sheets β31 (left). B. Interactions of Osl in the MRJP1 oligomer; four Osl (ostreasterol or methylenecholesterol) molecules in the surface potential of MRJP1; interactions of the inner two Osl molecules with MRJP1 and apisimin (left). MRJP1 is the most abundant protein in royal jelly. It can exists in two forms, as monomer (single structure) and as oligomer (combined structure). The molecular size of the oligomer is 290-350 kDa.
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Polytrimethylene terephthalate (PTT), is a polyester synthesized and patented in 1941.John Rex Whinfield and James Tennant Dickson (1941) "Improvements Relating to the Manufacture of Highly Polymeric Substances", UK Patent 578,079; "Polymeric Linear Terephthalic Esters", Publication date: March 22, 1949; Filing date: September 24, 1945; Priority date: July 29, 1941 It is produced by a method called condensation polymerization or transesterification. The two monomer units used in producing this polymer are: 1,3-propanediol and terephthalic acid or dimethyl terephthalate. Similar to polyethylene terephthalate, the PTT is used to make carpet fibers.
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This strain is transmitted to the remaining three monomers in the tetramer, where it induces a similar conformational change in the other heme sites such that binding of oxygen to these sites becomes easier. As oxygen binds to one monomer of hemoglobin, the tetramer's conformation shifts from the T (tense) state to the R (relaxed) state. This shift promotes the binding of oxygen to the remaining three monomer's heme groups, thus saturating the hemoglobin molecule with oxygen. In the tetrameric form of normal adult hemoglobin, the binding of oxygen is, thus, a cooperative process.
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In this example, monomer "A" is said to dimerise to give the dimer "A-A". An example is a diaminocarbene, which dimerise to give a tetraaminoethylene: :2 C(NR2)2 → (R2N)2C=C(NR2)2 Carbenes are highly reactive and readily form bonds. Dicyclopentadiene is an asymmetrical dimer of two cyclopentadiene molecules that have reacted in a Diels-Alder reaction to give the product. Upon heating, it "cracks" (undergoes a retro-Diels-Alder reaction) to give identical monomers: :C10H12 → 2 C5H6 Many nonmetallic elements occur as dimers: hydrogen, nitrogen, oxygen, the halogens, i.e.
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STM image of self-assembled supramolecular chains of the organic semiconductor quinacridone on graphite. One important property of carbon in organic chemistry is that it can form certain compounds, the individual molecules of which are capable of attaching themselves to one another, thereby forming a chain or a network. The process is called polymerization and the chains or networks polymers, while the source compound is a monomer. Two main groups of polymers exist: those artificially manufactured are referred to as industrial polymers or synthetic polymers (plastics) and those naturally occurring as biopolymers.
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Due to the high steric demand of the TMP ligand and its flexible rotation in solution, the THF molecule gets separated from the magnesium cation. The result is an unsaturated magnesium side that could explain the enhanced reactivity and selectivity of TMPMgCl·LiCl. TMP-Turbo- Hauser Base in THF solution Knochel et al. proposed that LiCl increases the reactivity of Turbo-Grignard compounds RMgCl·LiCl (R = alkyl, aryl or vinyl) by giving the reactive bimetallic monomer a magnesiate character in sense of a solvent separated ion pair (SSIP) [Li(THF)4]+ [RMg(THF)Cl2]−.
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Until the 1970s, Dynamit Nobel polymerised the monomer vinyl chloride into polyvinyl chloride (PVC) in the factory of Troisdorf. At this time, about 130 to 140 employees were regularly in touch with it. In total, about 3600 persons have worked within this division since the launching of the production in Troisdorf in the 1940s. Infringing the health and safety regulations in force at that time, the employees of Dynamit Nobel were exposed for years, with little protection, to this harmful substance which later turned out to be carcinogenic.
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N-(2-Hydroxypropyl)methacrylamide or HPMA is the monomer used to make the polymer poly(N-(2-hydroxypropyl)methacrylamide). Poly(N-(2-hydroxypropyl) methacrylamide); poly(HPMA); pHPMA; PHPMA The polymer is water-soluble (highly hydrophilic), non-immunogenic and non-toxic, and resides in the blood circulation well. Thus, it is frequently used as macromolecular carrier for low molecular weight drugs (especially anti-cancer chemotherapeutic agents) to enhance therapeutic efficacy and limit side effects. Poly(HPMA)-drug conjugate preferably accumulates in tumor tissues via the passive-targeting process (or so-called EPR effect).
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The 'stalk' is composed of a 14-strand β-barrel, with two strands donated from each monomer. A structure of the Vibrio cholerae cytolysin PDB:3O44 in the pore form is also heptameric; however, Staphylococcus aureus gamma-hemolysin (PDB:3B07) reveals an octomeric pore, consequently with a 16-strand 'stalk'. The Panton-Valentine leucocidin S structure (PDB: 1T5R) shows a highly related structure, but in its soluble monomeric state. This shows that the strands involved in forming the 'stalk' are in a very different conformation – shown in Fig 2.
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Common monomers utilized for 3D imaging include multifunctional acrylates and methacrylates, often combined with a non-polymeric component in order to reduce volume shrinkage. A competing composite mixture of epoxide resins with cationic photoinitiators is becoming increasingly used since their volume shrinkage upon ring-opening polymerization is significantly below those of acrylates and methacrylates. Free-radical and cationic polymerizations composed of both epoxide and acrylate monomers have also been employed, gaining the high rate of polymerization from the acryilic monomer, and better mechanical properties from the epoxy matrix.
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Cationically crosslinked ECC is used in a variety of industrial applications, due to its low viscosity, excellent electrical properties and high reliability among others as an electrical insulator, as coating and adhesive or as printing ink. Homopolymerized ECC, however, is extremely brittle, which is disadvantageous. This problem can be addressed by integration of elastomer particles in the epoxy matrix, such as rubber or silicone, by integration of inorganic fillers or by plasticization due to polymerization in the presence of polyester polyols. The latter are covalently integrated via the monomer-activated mechanism into the polymer network.
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Polyacrylamide (IUPAC poly(2-propenamide) or poly(1-carbamoylethylene), abbreviated as PAM) is a polymer (-CH2CHCONH2-) formed from acrylamide subunits. It can be synthesized as a simple linear-chain structure or cross- linked, typically using N,N-methylenebisacrylamide. In the cross-linked form, the possibility of the monomer being present is reduced even further. It is highly water-absorbent, forming a soft gel when hydrated, used in such applications as polyacrylamide gel electrophoresis, and can also be called ghost crystals when cross-linked, and in manufacturing soft contact lenses.
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2,6-Xylenol is a monomer for poly(p-phenylene oxide) engineering resins through carbon - oxygen oxidative coupling. Carbon-to- carbon dimerization is also possible. In one study 2,6-xylenol is oxidized with iodosobenzene diacetate with a fivefold excess of the phenol.Selective oxidative para C–C dimerization of 2,6-dimethylphenol Christophe Boldron, Guillem Aromí, Ger Challa, Patrick Gamez and Jan Reedijk Chemical Communications, 2005, (46), 5808 - 5810 Abstract In the first step of the proposed reaction mechanism the acetyl groups in the iodine compound are replaced with the phenol.
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The structure of a PLA1 is a monomer that contains the following sequence: Gly-X-Ser-X-Gly, where X represents any other amino acid. The serine is considered the active site in the enzyme. PLA1's also contain a catalytic triad of Ser-Asp-His, with a variety of cysteine residues needed for disulfide bond formation. The cysteine residues are responsible for key structural motifs such as the lid domain and the B9 domain, both of which are lipid binding surface loops. These two loops can vary between each PLA1.
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The core cyanobacterial circadian oscillator, encoded by the kaiA, kaiB, and kaiC genes, regulates global patterns of gene expression and governs essential cellular processes including photosynthesis and cell division. Cyclic, sequential rhythms of KaiC phosphorylation and dephosphorylation constitute the oscillator’s timekeeping mechanism both in vivo and in vitro. KaiC is organized as a ring-shaped homohexamer. Each monomer component contains four essential structural motifs: a CI domain, a CII domain, a B-loop binding domain, and a tail that protrudes from the C-terminus known as the A-loop.
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The interleukin 2 receptor, which is involved in T cell-mediated immune responses, is present in 3 forms with respect to ability to bind interleukin 2. The low affinity form is a monomer of the alpha subunit (also called CD25) and is not involved in signal transduction. The intermediate affinity form consists of a gamma/beta subunit heterodimer, while the high affinity form consists of an alpha/beta/gamma subunit heterotrimer. Both the intermediate and high affinity forms of the receptor are involved in receptor-mediated endocytosis and transduction of mitogenic signals from interleukin 2.
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Alpha-toxin, also known as alpha-hemolysin (Hla), is the major cytotoxic agent released by bacterium Staphylococcus aureus and the first identified member of the pore forming beta-barrel toxin family. This toxin consists mostly of beta- sheets (68%) with only about 10% alpha-helices. The hly gene on the S. aureus chromosome encodes the 293 residue protein monomer, which forms heptameric units on the cellular membrane to form a complete beta-barrel pore. This structure allows the toxin to perform its major function, development of pores in the cellular membrane, eventually causing cell death.
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CHEN, Polymer Aluminum Electrolytic Capacitors with Chemically-Polymerized Polypyrrole (PPy) as Cathode Materials Part I. Effect of Monomer Concentration and Oxidant on Electrical Properties of the Capacitors, PDF or PEDOTU. Merker, K. Wussow, W. Lövenich, H. C. Starck GmbH, New Conducting Polymer Dispersions for Solid Electrolyte Capacitors, PDF are better by a factor of 1000 than that of manganese dioxide, and are close to the conductivity of metals. In 1993 NEC introduced their SMD polymer tantalum electrolytic capacitors, called "NeoCap". In 1997 Sanyo followed with their "POSCAP" polymer tantalum chips.
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Synthetic route for the production of the isoprene monomer from various starting materials Unfortunately the rubber from the Guayule plant did not satisfy the American demand for rubber. Even though President Franklin D. Roosevelt had stockpiled roughly 1 million tons of rubber, the annual U.S. consumption rate was 600 thousand tons of rubber. Therefore, additional rubber supplies were needed in order to avert a rubber shortage. This would present a serious vulnerability in the American war machine, as rubber was used to manufacture a wide variety of war materials.
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Total synthesis of (+)-Absinthin was conducted in 2004 by Zhang, et al. The final yield reported for the synthesis was 18.6% over a course of 10 steps originating from Santonin (1), a commercially available reagent. The basis of the synthesis was the ring expansion of the original 6-membered carbon ring to the 7-membered ring, engendering the formation of the guaianolide monomer (2) scaffold, followed by Diels Alder coupling (3) and final stereochemical modifications resulting in (+)-Absinthin (4). Illustration of the total synthesis conducted by Zhang, et al.
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The first stable intermediate in the biosynthesis pathway in Artemisia is likely Germacrene A [B], which has been previously identified in plant sesquiterpene pathways as a precursor to guaianolides. From there, hydroxylation (3) occurs, followed by oxidation (4) to an aldehyde directly followed by further hydroxylation (5) and formation of a carboxyl group. It is important to note the disappearance of the terminal carbon-carbon double bond after (4), as the reduction of this bond in the final product differentiates the Absinthin monomer from other Germacrene A downstream products.
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These interactions regulate the circadian oscillation by modulating the magnesium binding in KaiC. An alternative view for the core mechanism of this remarkable clock is based on observations of the ATPase activity of KaiC. KaiC hydrolyses ATP at the remarkably slow rate of only 15 ATP molecules per KaiC monomer per 24 hours. The rate of this ATPase activity is temperature compensated, and the activities of wild-type and period-mutant KaiC proteins are directly proportional to their in vivo circadian frequencies, suggesting that the ATPase activity defines the circadian period.
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