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PubMed2006

Poly(dimethylamino)ethyl methacrylate for use as a surfactant in the miniemulsion polymerization of styrene.

A novel Y-shaped macromonomer based on poly[(dimethylamino)ethyl methacrylate] (PDMAEMA) with a narrow molecular weight distribution was synthesized via oxyanion-initiated polymerization in which a potassium alcoholate of trimethylol propane allyl ether (2K-TMPAE) was used as a difunctional initiator. For the miniemulsion polymerization of styrene, this macromonomer acted well both as a comonomer carrying a reactive C=C double bond in its central section and as a pH-responsive polycationic surfactant in media with different pH values. The resulting microspheres composed of a hydrophobic polystyrene core and a hydrophilic PDMAEMA-protonated corona have shown spherical morphology and are quite stable. The nature of the reactive group, the amount of polymeric surfactant, and pH values in the aqueous medium have been systematically investigated during the miniemulsion polymerization by analyzing the evolution of the monomer conversions. The results of FTIR and (1)H NMR spectra demonstrated the generation of the functional particles. The analyses of TEM micrographs and dynamic light scattering (DLS) confirmed that the latices had a relatively narrow particle size distribution. The measurement of the zeta potential gave further evidence of the "hairy" particle structure. Because the reactive group is located in the central section of the macromonomer, the stabilization mechanism of the polymeric surfactant can be ascribed to (1) the absorption of two polycationic and hydrophilic tails that have electrostatic and steric stabilization to decrease the interface tension and (2) the copolymerization with the styrene monomer.

Journal Article↗
PubMed2006

Preparation of micrometer-sized polymer particles with control of initiator dissociation during soap-free emulsion polymerization.

A previously proposed method of soap-free emulsion polymerization employing an amphoteric initiator, 2,2'-azobis [N-(2-carboxyethyl)-2-methylpropionamidine] tetrahydrate (VA-057), was extended to synthesize micrometer-sized polystyrene particles with low polydispersity in an acidic region of pH from 3.3 to 4.6. A buffer system of CH3COOH/CH3COONa was used for the adjustment of pH, which was aimed at effective promotion of particle coagulation in early stage of the polymerization. In these experiments, CH3COOH concentration was varied from 20 to 360 mM at a CH3COONa concentration of 10 mM. Polymer particles with an average size of 1.8 microm and low polydispersity were obtained at the CH3COOH concentration of 40 mM for the concentrations of 1.1 M styrene monomer and 10 mM initiator. To more precisely control dispersion stability of particles, experiments in which pH was stepwisely changed during the polymerization were also carried out. This polymerization method could enhance the average size of particles to 2.2 microm while retaining the monodispersity of particles. Furthermore, combination of pH stepwise change and monomer addition during the polymerization could produce particles with an average size of 3.0 microm and low polydispersity.

Journal Article↗
PubMed2005

Polymerization past the N2-isopropylguanine and the N6-isopropyladenine DNA lesions with the translesion synthesis DNA polymerases eta and iota and the replicative DNA polymerase alpha.

The effects of N2-isopropylGua and N6-isopropylAde adducts in template DNA on polymerization by the human replicative DNA polymerase alpha (B-family) and the translesion synthesis DNA polymerases eta and iota (Y-family) were investigated. A direct comparison between the accuracies of DNA synthesis using catalytic fragments of the human DNA polymerases eta and iota is reported. We show that the N2-isopropylGua adduct is a powerful block to polymerization by DNA polymerase alpha. In contrast, the DNA polymerases eta and iota synthesize DNA past the N2-isopropylGua lesion with efficiencies and accuracies opposite the lesion comparable to the unadducted Gua. All three DNA polymerases bypass the N6-isopropylAde adduct with only modest effects on efficiencies and accuracy. These results illustrate the dramatically different consequences to polymerization conferred by the position of the isopropyl adduct when catalyzed by DNA polymerase alpha and the lack of this effect on polymerization by the translesion synthesis DNA polymerases eta and iota. A steady-state kinetic analysis of nucleotide insertion opposite the N2-isopropylGua and the N6-isopropylAde by the DNA polymerases eta and iota was performed to measure the accuracy of DNA synthesis at these lesions. This analysis showed that the DNA polymerases eta and iota preferably insert the correct nucleotide Cyt opposite the N2-isopropylGua lesion and the correct nucleotide Thy opposite the N6-isopropylAde with levels of accuracy similar to those detected opposite the unadducted nucleotides, thus, demonstrating minimal blocking and mutagenic potential by these lesions to the translesion synthesis polymerases. Similarly, a kinetic analysis of polymerization opposite the N6-isopropylAde by the DNA polymerase alpha showed comparable levels of insertion accuracy relative to the unadducted Ade. These results suggest that positioning of the isopropyl adduct on the purine ring to locate this group into the minor groove of the DNA is an important determinant to effect blocked replication by a replicative (B-family) polymerase, but not to affect replication by a translesion synthesis (Y-family) polymerase.

Adenine↗
PubMed1998

Isothermal and non-isothermal polymerization of a new bone cement.

A new bone cement based on poly(ethylmethacrylate) (PEMA), hydroxyapatite powder (HA) and n-butylmethacrylate monomer (n-BMA) has been studied using isothermal and non-isothermal polymerization. Methacrylate monomers are highly reactive and release a considerable amount of heat during polymerization. A quantitative understanding of the methacrylate polymerization is necessary because the thermal history of the polymerization has considerable influence on the final properties of a bone cement. In the first part, polymerization kinetics are analysed by means of differential scanning calorimetry (DSC). DSC data are used to evaluate a phenomenological model describing the cure kinetics of this new bone cement. In the second part, a kinetic model coupled with the energy balance is used to obtain temperature and degree of conversion profiles in the bone-cement-prosthesis system, under non-isothermal conditions, as function of initial temperature and thickness of the cement. Material properties, boundary and initial conditions and the kinetic behaviour are the input data for the numerically solved heat-transfer model. The temperature at the bone/cement interface, can be considered as a weak point, often responsible for total joint replacement failure. For this particular bone cement exhibiting a low exotherm and low glass transition temperature, the interfacial temperature is lower than the threshold level for thermal tissue damage (50 degrees C). The conversion occurs almost completely, avoiding problems with unreacted monomers that can be released by the cement, giving rise to tissue damage.

Journal Article↗
PubMed1998

Visualization of PEO-PBLA-pyrene polymeric micelles by atomic force microscopy.

PURPOSE: To directly visualize and evaluate the aqueous block copolymeric micelles, poly(ethylene oxide)-poly(beta-benzyl L-aspartate) (PEO-PBLA) chemically conjugated with pyrene fluorescence molecule, by nanotechnology of atomic force microscopy (AFM). METHODS: The block copolymers' PEO-PBLA-Pyrene was first synthesized by reacting with pyrene sulfonyl chloride and PEO-PBLA in tetrahydrofuran (THF) solution and were identified by GPC reflect index, UV and fluorescence detectors. The characterization of physical and chemical properties of PEO-PBLA-Pyrene polymeric micellar solution were examined by the dynamic light scattering (DLS) and critical micelles concentrations (CMC). In addition, the nanotechnology of AFM was used to directly visualize the size and shape of nanopolymeric micelles. RESULTS: The pyrene fluorescence molecule were successfully conjugated at the amino group of the end of PBLA chain by GPC with three different detectors. The size of the aqueous PEO-PBLA-Pyrene polymeric micelles was detected around 57 nm with unimodal distribution by DLS measurement. As a result of this finding, the CMC test was also found out that the fluorescence intensity was increasing around 0.01 approximately 0.05 mg/ml. Using AFM evaluation of polymeric micellar solution, the morphology of aqueous PEO-PBLA-Pyrene polymeric micelles was observed on round shape and with the narrow dispersity of size range 50 approximately 80 nm. CONCLUSIONS: The presence of PEO-PBLA copolymers with pyrene in an aqueous system formed in a spherical and nano range of polymeric micelles.

Micelles↗
PubMed1990

Evolution of a polymeric globin in the brine shrimp Artemia.

Several invertebrate species possess haemoglobins in which each polypeptide contains multiple haem-binding domains, possibly reflecting the fusion of multiple monomeric globin transcriptional units at the gene level. We have now analysed the transcript of such a polymeric globin gene from the brine shrimp Artemia, which expresses three polymeric haemoglobins, each of relative molecular mass 260,000 (Mr 260K). These are formed by the variable association of two different subunit types, alpha and beta (refs 2,3). Haemoglobins I and III are homodimers of alpha and beta subunit types, respectively, and haemoglobin II is a heterodimer (alpha beta). The individual globin chains are of similar size (Mr 130K), but the exact nature of the differences between the two subunit types is unclear. Analysis of complementary DNA clones encoding one of the subunits of the Artemia dimeric haemoglobin showed that the globin messenger RNA encodes nine myoglobin-like domains, connected by linking peptides. The residues in the linkers are characteristic of those found generally in such protein linkers, and include turn-promoting amino acids. Each domain also contains the conserved residues that are required for functional haem-binding, and from analysis of the sequences it was predicted that they all can adopt the classic myoglobin-like fold. Analysis of the derived amino-acid sequences indicated that the individual domains are duplicated monomers that fused to form the polymeric globin some 200 Myr ago. The fusion of multiple transcriptional units for the evolution of a polymeric globin gene may have been a general mechanism for the appearance of such polymeric haemoglobins in invertebrates.

Amino Acid Sequence↗
PubMed1972

Solubilization of a mannose-polymerizing enzyme from Phaseolus aureus.

A soluble enzyme preparation, which catalyses the polymerization of mannose, was obtained by Triton X-100 extraction of a particulate fraction derived from Phaseolus aureus hypocotyls. The product that resulted when GDP-alpha-d-mannose was used as a substrate was a beta-(1-->4)-linked mannan, about three-quarters of which was alkali-insoluble. The mannose-polymerizing enzyme activity was at least as great in the soluble preparation as in the particulate preparation, and the specific activity of the solubilized enzyme was greater by a factor of at least 3.5. Kinetic studies of the soluble enzyme indicate that the apparent K(m) is 55-62mum, and a disproportionate increase in rate is observed at high concentrations. GDP-alpha-d-glucose is a strong competitive inhibitor of the mannose-polymerizing reaction, with an apparent K(i) of 6.2mum. The soluble enzyme is relatively unstable, losing about two-thirds of its original activity in 5h at 0 degrees C or in 24h at -20 degrees C. A solvent (acetone, butanol, diethyl ether)-extracted particulate preparation, which also exhibits the same enzyme activity, is more stable, retaining full activity for at least 5 days at -20 degrees C. There was no polymerizing-enzyme activity in the soluble enzyme preparation when UDP-d-glucose, UDP-d-galactose, UDP-d-xylose, UDP-l-arabinose or UDP-d-glucuronic acid were used as substrates. However, the soluble enzyme preparation would catalyse the polymerization of glucose, with GDP-d-glucose as substrate.

Arabinose↗
PubMed1972

The control of ribonucleic acid synthesis in bacteria. Polymerization rates for ribonucleic acids in amino acid-starved relaxed and stringent auxotrophs of Escherichia coli.

Polymerization rates of newly formed chains of various RNA fractions were measured in Escherichia coli CP78 (RC(str)) and CP79 (RC(rel)) multiple amino acid auxotrophs, deprived of four amino acids essential for growth. Immediately after the onset of severe amino acid deprivation, in RC(str) strains the rate of labelling of RNA by exogenous nucleotide bases was greatly diminished. At first, the initiation of new RNA chains declined faster than the rate of polymerization in RC(str) organisms, but as starvation proceeded the rate of polymerization was eventually lowered to about 10% of that found during normal growth. In strain CP79 (RC(rel)), on the other hand, chain-polymerization rates were unaffected by amino acid withdrawal. Artificial depletion of the intracellular purine nucleotide pools in RC(str) or RC(rel) strains by trimethoprim, before the onset of amino acid deprivation, showed that in the RC(str), but not the RC(rel) strain, amino acid withdrawal gave rise to an inability of the cells to utilize exogenously supplied purine or pyrimidine bases for RNA synthesis. During a prolonged starvation, the observed 100-fold decrease in the total rate of incorporation of exogenous nucleotide bases into the RNA of RC(str) organisms was ascribed to a combination of a tenfold decrease in the overall rate of RNA chain polymerization, at least a fivefold decrease in the ability of the cells to utilize exogenous bases and a preferential inhibition of initiation of stable RNA chains. None of these changes occurred in the corresponding RC(rel) strain.

Adenine↗
PubMed1985

Effects of temperature on actin polymerized by Ca2+. Direct evidence of fragmentation.

When the temperature is lowered from 20 to 4 degrees C, the specific viscosity of actin polymerized in the presence of either 4 mM-CaCl2 or 2 mM-MgCl2, but not of actin polymerized in the presence of 90 mM-KCl, is decreased by 50% in the absence of free ATP. Addition of ATP restores the viscosity of the actin polymerized by Mg2+, but not that of actin polymerized by Ca2+, to the original value. The effect of temperature on actin polymerized in the presence of Ca2+ is due to (a) polymer-into-monomer conversion, (b) latero-lateral aggregation of filaments, and (c) fragmentation of the filaments. Fragmentation, as demonstrated by fractional centrifugation and electron microscopy, was the most important of these.

Actins↗
PubMed2001

Sound attenuation of polymerizing actin reflects supramolecular structures: viscoelastic properties of actin gels modified by cytochalasin D, profilin and alpha-actinin.

Polymerization and depolymerization of cytoskeletal elements maintaining cytoplasmic stiffness are key factors in the control of cell crawling. Rheometry is a significant tool in determining the mechanical properties of the single elements in vitro. Viscoelasticity of gels formed by these polymers strongly depends on both the length and the associations of the filaments (e.g. entanglements, annealings and side-by-side associations). Ultrasound attenuation is related to viscosity, sound velocity and supramolecular structures in the sample. In combination with a small glass fibre (2 mm x 50 microm), serving as a viscosity sensor, an acoustic microscope was used to measure the elasticity and acoustic attenuation of actin solutions. Changes in acoustic attenuation of polymerizing actin by far exceed the values expected from calculations based on changes in viscosity and sound velocity. During the lag-phase of actin polymerization, attenuation slightly decreases, depending on actin concentration. After the half-maximum viscosity is accomplished and elasticity turns into steady state, attenuation distinctly rises. Changes in ultrasound attenuation depend on actin concentration, and they are modulated by the addition of alpha-actinin, cytochalasin D and profilin. Thus absorption and scattering of sound on the polymerization of actin is related to the packing density of the actin net, entanglements and the length of the actin filaments. Shortening of actin filaments by cytochalasin D was also confirmed by electron micrographs and falling-ball viscosimetry. In addition to viscosity and elasticity, the attenuation of sound proved to be a valuable parameter in characterizing actin polymerization and the supramolecular associations of F-actin.

Acoustics↗
PubMed1999

Influence of polymerization initiator for base monomer on microwave curing of composite resin inlays.

Microwave polymerization was used to make composite resin inlays and the effect examined of the concentration of polymerization initiator for the base monomer. The monomers used were 2,2-bis [4-(3-methacriloxy-2-hydroxypropoxy) phenyl] propane (Bis-GMA) and triethyleneglycol dimethacrylate (TEGDMA). Bis-GMA and TEGDMA were mixed in a ratio of 6:4 by weight and were separated into five groups. To each group was added benzoyl peroxide (BPO) in the ratios of 0.1, 0.3, 0.5, 0.7 and 0.9 wt% as the polymerization initiator. These were used as the base monomers. The results showed that the degree of conversion of the cured sample increased with increasing concentration of BPO from 0.1 to 0.5 wt%, however there was no significant difference at 0.5, 0.7 and 0.9 wt% (P> 0.01). Compression strength, diametral tensile strength and the Knoop hardness showed a similar tendency as the degree of conversion. No significant difference was recorded in the Knoop hardness between the top and the bottom surfaces (P> 0.01), which suggested a uniform polymerization in the cured sample. Thus, microwave polymerization would be an efficacious method for making resin inlays with the addition of BPO to the base monomer (Bis-GMA:TEGDMA, 6:4). The maximum conversion was found at a concentration of 0.5 wt%.

Benzoyl Peroxide↗
PubMed2006

Influence of the reaction mechanism on the time course of the entropy production during reversible polymerization.

The paper shows the influence of the reaction mechanism on the time course of the entropy production sigma in a closed system during reversible polymerization. We consider two different reaction mechanisms with (a) being a polycondensation and (b) a chain growth mechanism. For both mechanisms explicit expressions for the entropy production sigma as a function of time t are derived. To demonstrate the application of these general expressions we consider two different polymerization experiments where the reaction starts (i) from monomer molecules polymerizing to a defined number average chain length x(n,eq) and (ii) from monodisperse polymer molecules reacting with each other under the constraint that x(n) is the same at the beginning and the end of the reaction. In both cases we treat the system to be ideal and describe the kinetics of the reversible polymerization reactions using two kinetic constants for the forward and backward reactions, respectively. Under these assumptions the difference in the curvature of the entropy production sigma between a polycondensation and a chain growth mechanism is only marginal if the reaction starts from monomer molecules polymerizing to a defined number average chain length x(n,eq).

Journal Article↗
PubMed2000

Effect of water temperature during polymerization on strength of autopolymerizing resin.

STATEMENT OF PROBLEM: Breakage is a potential problem of provisional resin restorations. A method that effectively increases the strength of the resin is desirable. PURPOSE: This study examined the effects of the curing environment, air or water, and water temperature during polymerization on the mechanical properties of autopolymerizing resin. MATERIAL AND METHODS: After mixing the autopolymerizing methyl methacrylate resin for 10 seconds, it was placed in a stainless steel mold (2 x 2 x 25 mm). One minute and 50 seconds after the start of mixing, the mold containing the resin was placed under the following conditions: in air at 23 degrees C; or in water at 10 degrees C, 23 degrees C, 30 degrees C, 40 degrees C, 60 degrees C, and 80 degrees C. Six minutes after mixing began, the resin specimen was removed from the mold and the transverse test (3-point flexural test) was performed. RESULTS: Alteration of conditions during polymerization revealed a significant effect on both the transverse strength and modulus of the resin (P <.0001). Both increased with an increase in water temperature. Water conditions of 60 degrees C to 80 degrees C produced more than 2 times greater transverse strength and modulus of the resin compared with polymerization in 23 degrees C air (P <.0001). CONCLUSION: Polymerization of the resin in hot water greatly increased its mechanical properties. The method of placing resin restorations in hot water during polymerization may be useful for improving mechanical requirements and obtaining long-lasting performance.

Acrylic Resins↗
PubMed2006

Metallocene-catalyzed alkene polymerization and the observation of Zr-allyls.

Single-site polymerization catalysts enable exquisite control over alkene polymerization reactions to produce new materials with unique properties. Knowledge of catalyst speciation and fundamental kinetics are essential for full mechanistic understanding of zirconocene-catalyzed alkene polymerization. Currently the effect of activators on fundamental polymerization steps is not understood. Progress in understanding activator effects requires determination of fundamental kinetics for zirconocene catalysts with noncoordinating anions such as [B(C6F5)4]-. Kinetic NMR studies at low temperature demonstrate a very fast propagation rate for 1-hexene polymerization catalyzed by [(SBI)Zr(CH2SiMe3)][B(C6F5)4] [where SBI is rac-Me2Si(indenyl)2] with complete consumption of 1-hexene before the first NMR spectrum. Surprisingly, the first NMR spectrum reveals, aside from uninitiated catalyst, Zr-allyls as the sole catalyst-containing species. These Zr-allyls, which exist in two diastereomeric forms, have been characterized by physical and chemical methods. The mechanism of Zr-allyl formation was probed with a trapping experiment, leading us to favor a mechanism in which Zr-polymeryl undergoes beta-H transfer to metal without dissociation of coordinated alkene followed by sigma-bond metathesis to form H2 and Zr-allyl. Zr-allyl species undergo slow reactions with alkene but react rapidly with H2 to form hydrogenation products.

Journal Article↗
PubMed1983

Polymerization of actin: mechanism of the Mg2+-induced process at pH 8 and 20 degrees C.

A detailed mechanism that fully accounts for the Mg2+-induced polymerization of actin in the presence or absence of Ca2+ at 20 degrees C and pH 8 is presented. In the absence of Ca2+, the mechanism of the Mg2+-induced polymerization is as follows: Mg2+ binds to a metal-binding site on G-actin and induces a conformational change, which is required for eventual polymerization. The overall dissociation constant for this binding is about 30 microM. This actin species then binds a second molecule of Mg2+ (Kd = 5 mM), which yields a species capable of polymerization. Dimer formation from this monomeric species is quite unfavorable, but trimer formation from dimer and monomer is much more favorable. The trimer may then elongate to give filaments. Ca2+, when present, binds at the same site as the tightly bound Mg2+ and must be displaced by Mg2+ before the conformational change can occur. The rate and dissociation constants for tight binding of Ca2+ and Mg2+ and for the conformational change are consistent with those observed previously by using a fluorescently labeled G-actin. With the mechanism proposed, it is possible to fit the full time course of polymerization over a wide range of actin concentrations, Mg2+ concentrations, and Ca2+ concentrations.

Actins↗
PubMed1998

The Arp2/3 complex mediates actin polymerization induced by the small GTP-binding protein Cdc42.

The small GTP-binding protein Cdc42 is thought to induce filopodium formation by regulating actin polymerization at the cell cortex. Although several Cdc42-binding proteins have been identified and some of them have been implicated in filopodium formation, the precise role of Cdc42 in modulating actin polymerization has not been defined. To understand the biochemical pathways that link Cdc42 to the actin cytoskeleton, we have reconstituted Cdc42-induced actin polymerization in Xenopus egg extracts. Using this cell-free system, we have developed a rapid and specific assay that has allowed us to fractionate the extract and isolate factors involved in this activity. We report here that at least two biochemically distinct components are required, based on their chromatographic behavior and affinity for Cdc42. One component is purified to homogeneity and is identified as the Arp2/3 complex, a protein complex that has been shown to nucleate actin polymerization. However, the purified complex alone is not sufficient to mediate the activity; a second component that binds Cdc42 directly and mediates the interaction between Cdc42 and the complex also is required. These results establish an important link between a signaling molecule, Cdc42, and a complex that can directly modulate actin networks in vitro. We propose that activation of the Arp2/3 complex by Cdc42 and other signaling molecules plays a central role in stimulating actin polymerization at the cell surface.

Actin-Related Protein 2↗
PubMed1997

Severely impaired polymerization of recombinant fibrinogen gamma-364 Asp --> His, the substitution discovered in a heterozygous individual.

During blood coagulation, soluble fibrinogen is converted to fibrin monomers that polymerize to form an insoluble clot. Polymerization has been described as a two-step process: the formation of double-stranded protofibrils and the subsequent lateral aggregation of protofibrils into fibers. Previous studies have shown that gamma chain residues Tyr-363 and Asp-364 have a significant role in polymerization, most likely in protofibril formation. To better define the role of these residues, we synthesized three fibrinogens with single substitutions at these two positions: Tyr-363 --> Ala, Asp-364 --> Ala, and Asp-364 --> His. We found that the release of fibrinopeptides A and B was the same for these variants and normal recombinant fibrinogen, showing that all variants had normal fibrin formation. In contrast, we found that polymerization was significantly delayed for both Ala variants and was almost nonexistent for the His variant. Clottability for the Ala variants was only slightly reduced, and fibrin gels were formed. Surprisingly, clottability of the His variant was substantially reduced, and fibrin gels were not formed. Our data suggest that both protofibril formation and lateral aggregation were altered by these substitutions, indicating that the C-terminal domain of the gamma chain has a role in both polymerization steps.

Amino Acid Substitution↗
PubMed1999

Structural requirements for polymeric immunoglobulin assembly and association with J chain.

Both IgM and IgA exist as polymeric immunoglobulins. IgM is assembled into pentamers with J chain and hexamers lacking J chain. In contrast, polymeric IgA exists mostly as dimers with J chain. Both IgM and IgA possess an 18-amino acid extension of the C terminus (the tail-piece (tp)) that participates in polymerization through a penultimate cysteine residue. The IgM (mutp) and IgA (alphatp) tail-pieces differ at seven amino acid positions. However, the tail-pieces by themselves do not determine the extent of polymerization. We now show that the restriction of polymerization to dimers requires both C(alpha)3 and alphatp and that more efficient dimer assembly occurs when C(alpha)2 is also present; the dimers contain J chain. Formation of pentamers containing J chain requires C(mu)3, C(mu)4, and the mutp. IgM-alphatp is present mainly as hexamers lacking J chain, and mumugammamu-utp forms tetramers and hexamers lacking J chain, whereas IgA-mutp is present as high order polymers containing J chain. In addition, there is heterogeneous processing of the N-linked carbohydrate on IgA-mutp, with some remaining in the high mannose state. These data suggest that in addition to the tail-piece, structural motifs in the constant region domains are critical for polymer assembly and J chain incorporation.

Amino Acid Sequence↗