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PubMed2005

UV-vis spectroscopy for following the kinetics of homogeneous polymerization of diphenylamine in p-toluene sulphonic acid.

Kinetics of chemical oxidative polymerization of diphenylamine (DPA) was followed in aqueous 1M para-toluene sulphonic acid (p-TSA) using potassium peroxomonosulphate (PMS) or peroxodisulphate (PDS), independently as an oxidant. The medium was found to be homogeneous and became dark green in colour during the course of polymerisation. The course of polymerization was followed by UV-vis spectroscopy. Rate of polymerization (R(p)) was determined for various conditions by following the absorbance values corresponding to poly(diphenylamine) (PDPA) for different concentrations of DPA and PMS or PDS at various time intervals of polymerization. The observed dependences of DPA, PDS or PMS on R(p) were used to deduce rate equations for PDS or PMS initiated polymerization of DPA. The rate constant for the formation of poly(diphenylamine), was estimated. In situ spectroelectrochemical studies on the polymerization of DPA were also carried out on an ITO electrode in 1M p-TSA. The results are in accordance with the intermediates suggested in chemical oxidative polymerization.

Benzenesulfonates↗
PubMed2004

Two monoclonal antibodies to D-dimer-specific inhibitors of fibrin polymerization.

D-dimer of human fibrin was used as antigen to obtain monoclonal antibodies (mAbs). We have obtained 16 hybridomas producing mAbs of different specificity. Only two of these mAbs inhibited fibrin polymerization. They are of the IgG-class. One mAb (II-4d) inhibited fibrin polymerization to 100% and another (II-3b) to 60% at a molar ratio mAb/fibrin=1.0. Fab-fragments of these mAbs inhibited fibrin polymerization completely at the same molar ratio. The epitopes for the mAbs studied are situated in the NH2-terminal part of the gamma-chain in fibrin D-domain. Electron microscopy showed that fibrin was in monomeric form in the presence of these mAbs or their Fab-fragments. Thus, these mAbs stop the initial step of fibrin polymerization, i.e. protofibril formation. Only one site of protofibril formation is known now in COOH-terminal half of the D-domain gamma chain named "a" site, which is complementary to the "A" site in the central E-domain of fibrin molecule. Our experiment with immobilized GPRP showed that the "a" site in fibrin D-fragment preserved its binding activity to GPRP when the D-fragment was complexed with mAbs-inhibitors of fibrin polymerization. Thus, these two mAbs inhibit fibrin polymerization not by blocking the sites "a" but either by blocking another (not "a") specific site in D-domain or by steric hindrance of highly organized fibrin polymerization process.

Antibodies, Monoclonal↗
PubMed2000

Molecular basis for the polymerization of octopus lens S-crystallin.

S-Crystallin from octopus lens has a tertiary structure similar to sigma-class glutathione transferase (GST). However, after isolation from the lenses, S-crystallin was found to aggregate more easily than sigma-GST. In vitro experiments showed that the lens S-crystallin can be polymerized and finally denatured at increasing concentration of urea or guanidinium chloride (GdmCl). In the intermediate concentrations of urea or GdmCl, the polymerized form of S-crystallin is aggregated, as manifested by the increase in light scattering and precipitation of the protein. There is a delay time for the initiation of polymerization. Both the delay time and rate of polymerization depend on the protein concentration. The native protein showed a maximum fluorescence emission spectrum at 341 nm. The GdmCl-denatured protein exhibited two fluorescence maxima at 310 nm and 358 nm, respectively, whereas the urea-denatured protein showed a fluorescence peak at 358 nm with a small peak at 310 nm. The fluorescence intensity was quenched. Monomers, dimers, trimers, and polymers of the native protein were observed by negative-stain electron microscopic analysis. The aggregated form, however, showed irregular structure. The aggregate was solubilized in high concentrations of urea or GdmCl. The redissolved denatured protein showed an identical fluorescence spectrum to the protein solution that was directly denatured with high concentrations of urea or GdmCl. The denatured protein was readily refolded to its native state by diluting with buffer solution. The fluorescence spectrum of the renatured protein solution was similar to that of the native form. The phase diagrams for the S-crystallin in urea and GdmCl were constructed. Both salt concentration and pH value of the solution affect the polymerization rate, suggesting the participation of ionic interactions in the polymerization. Comparison of the molecular models of the S-crystallin and sigma-GST suggests that an extra ion-pair between Asp-101 and Arg-14 in S-crystallin contributes to stabilizing the protomer. Furthermore, the molecular surface of S-crystallin has a protruding Lys-208 on one side and a complementary patch of aspartate residues (Asp-90, Asp-94, Asp-101, Asp-102, Asp-179, and Asp-180) on the other side. We propose a molecular model for the S-crystallin polymer in vivo, which involves side-by-side associations of Lys-208 from one protomer and the aspartate patch from another protomer that allows the formation of a polymeric structure spontaneously into a liquid crystal structure in the lens.

Animals↗
PubMed1998

Effect of film composition and various penetration enhancers concentrations on prazosin release from acrylic polymeric films.

An investigation was conducted to evaluate the effect of changing the Eudragit RL 100 ratio and the influence of different penetration enhancers in various concentrations on the release of prazosin from Carboset 525:Eudragit RL 100 polymeric films using improved Franz diffusion cells, to choose the most suitable polymeric film ratio, the most appropriate enhancer and its optimum concentration to be used to achieve the maximum release of the drug. The results show that prazosin release from polymeric films containing Carboset 525:Eudragit RL 100 in a 1:1 ratio was significantly (p < 0.05) higher than from films in a 1:0.25 ratio and non-significantly (p > 0.05) higher than from those containing 1:0.5, 1:3 polymer ratios and non-significantly lower from those containing 1:4 polymer ratios. The addition of various enhancers, n-decyl alcohol (7, 9 and 11% w/w), Azone (4, 6 and 8% w/w) and Cineole (7, 9, 11 and 14% w/w) significantly (p < 0.05) enhanced the prazosin release from these polymeric films containing the two polymers in a 1:1 ratio. The best concentrations of these enhancers were 11% n-decyl alcohol, 9% Cineole and 8% Azone. The formulations containing these concentrations of the enhancers are being further studied for drug release through rabbits skin. It was found that using either of these enhancers in these concentrations resulted in a significant (p < 0.05) increase in the amount of prazosin transported across the skin. On the other hand these enhancers did not show any significant (p > 0.05) difference between them. The mechanism of drug release from the polymeric films was further studied using water vapor permeability (W.V.P.), the permeability constant (P) and differential scanning calorimetry. The enhancers were found to increase the W.V.P. and the permeability constant (P) and the results were in very good agreement with the effect of enhancers on the in-vitro drug release. The DSC thermograms showed that the enhancers physically interacted with either or both of the polymeric film materials and prazosin which could be one of the reasons for the improvement in the release of the drug from these polymeric films.

Acrylic Resins↗
PubMed2000

Characterization of resin composites polymerized with plasma arc curing units.

OBJECTIVES: Newly developed curing units (plasma arc curing units) operate at relatively high intensity and are claimed to result in optimum properties of resin composites in a short cure time. This study was conducted to determine a number of characteristics of resin composites polymerized by plasma arc curing units. METHODS: The investigated polymerization characteristics were quantity of remaining double bonds, depth of polymerization, flexural strength and modulus, and wall-to-wall polymerization contraction. The investigated plasma arc curing units were Apollo 95E and 1000 PAC. The conventional curing unit XL 3000 was used as baseline. RESULTS: Irradiation with Apollo 95E resulted in a higher quantity of remaining double bonds than did XL 3000, whereas the results obtained with 1000 PAC depended on the resin composite. The depth of cure with the plasma arc units was equal to or less than that obtained with the conventional unit, depending on the resin composite. The flexural strength did not depend on the curing unit. The flexural modulus resulting from curing with Apollo 95E was less than that resulting from curing with XL 3000 in 3 out of 4 comparisons. The wall-to-wall polymerization contraction was equal to or less with the plasma arc units than with the conventional unit. SIGNIFICANCE: Plasma arc curing units make it possible to polymerize resin composite in much shorter times than conventional curing units. However, the polymerization characteristics associated with the units may be less than optimal.

Composite Resins↗
PubMed1999

Post-irradiation polymerization of composites containing bis-GMA and TEGDMA.

OBJECTIVE: This study was conducted to evaluate the effect of the amount of TEGDMA on post-irradiation polymerization of bis-GMA based composites. METHODS: Four experimental composites containing bis-GMA and TEGDMA at the ratios (w/w) of 75/25, 70/30, 67/33, and 50/50 were prepared. The degree of conversion of each composite was measured by Fourier transformation infrared spectroscopy immediately after being cured and after 24 h of storage, and the post-irradiation polymerization was determined. In addition, the change in respective amounts of residual bis-GMA and TEGDMA in cured specimens over 24 h was determined by high performance liquid chromatography. Data were analyzed by means of ANOVA, followed by a Fisher's PLSD test at a significance level of 0.05. RESULTS: At both stages of as-cured and after 24 h-sotrage, the composites containing greater amounts of TEGDMA showed a greater degree of conversion. The amount of post-irradiation polymerization decreased as the content of the incorporated TEGDMA increased. The reduction in the amount of TEGDMA remaining unreacted during post-irradiation polymerization also decreased as the content of TEGDMA increased, while the amount of unreacted bis-GMA showed almost constant values. SIGNIFICANCE: An increase in the amount of TEGDMA-incorporation in bis-GMA based composites resulted in less post-irradiation polymerization. As the change in the amount of residual unreacted TEGDMA in cured specimens showed the same trend as the results of the post-irradiation polymerization. TEGDMA is considered to be the main contributor to post-irradiation polymerization of bis-GMA based composites.

Analysis of Variance↗
PubMed2002

High power light emitting diode (LED) arrays versus halogen light polymerization of oral biomaterials: Barcol hardness, compressive strength and radiometric properties.

The clinical performance of light polymerized dental composites is greatly influenced by the quality of the light curing unit (LCU) used. Commonly used halogen LCUs have some specific drawbacks such as decreasing light output with time. This may result in a low degree of monomer conversion of the composites with negative clinical implications. Previous studies have shown that blue light emitting diode (LED) LCUs have the potential to polymerize dental composites without having the drawbacks of halogen LCUs. Since these studies were carried out LED technology has advanced significantly and commercial LED LCUs are now becoming available. This study investigates the Barcol hardness as a function of depth, and the compressive strength of dental composites that had been polymerized for 40 or 20s with two high power LED LCU prototypes, a commercial LED LCU, and a commercial halogen LCU. In addition the radiometric properties of the LCUs were characterized. The two high power prototype LED LCUs and the halogen LCU showed a satisfactory and similar hardness-depth performance whereas the hardness of the materials polymerized with the commercial LED LCU rapidly decreased with sample depth and reduced polymerization time (20 s). There were statistically significant differences in the overall compressive strengths of composites polymerized with different LCUs at the 95% significance level (p = 0.0016) with the two high power LED LCU prototypes and the halogen LCU forming a statistically homogenous group. In conclusion, LED LCU polymerization technology can reach the performance level of halogen LCUs. One of the first commercial LED LCUs however lacked the power reserves of the high power LED LCU prototypes.

Biocompatible Materials↗
PubMed2001

The regulation of actin polymerization and cross-linking in Dictyostelium.

It is clear that the polymerization and organization of actin filament networks plays a critical role in numerous cellular processes. Inhibition of actin polymerization by pharmacological agents will completely prevent chemotactic motility, macropinocytosis, endocytosis, and phagocytosis. Recently there has been great progress in understanding the mechanisms that control the assembly and structure of the actin cytoskeleton. Members of the Rho family of GTPases have been identified as major players in the signal transduction pathway leading from a cell surface signal to actin polymerization. The Arp2/3 complex has been added to the list of means by which new actin filaments can be nucleated. However, it is clear that actin polymerization by Arp2/3 complex is not the whole story. In principle, the final structures formed by actin filaments will depend on factors such as: the length of actin filaments, the degree of branching, how they are cross-linked and the tensions imparted on them. In addition, the means by which actin polymerization generates protrusion of membranes is still controversial. A phagosome, filopodium and a lamellipodium all require polymerization of new actin filaments, but each has a characteristic morphology and cytoskeletal structure. In the following chapter, we will discuss actin polymerization and filament organization, especially as it relates to the machinery of phagocytosis in Dictyostelium.

Actin Cytoskeleton↗
PubMed1999

Involvement of lipids in ferriprotoporphyrin IX polymerization in malaria.

Approximately 70% of the initial ferriprotoporphyrin IX polymerizing activity in cell-free preparations of erythrocytes infected with Plasmodium berghei was recovered in a chloroform extract. No polymerizing activity remained in the residue. In studies to identify substances that promote FP polymerization, arachidonic, linoleic, oleic, and palmitoleic acids, 1-mono- and di-oleoylglycerol, and the detergents, SDS, Tween 80, and n-octyl-glucopyranoside, were active. Tri-oleoylglycerol, cholesterol, di-oleoylphosphatidylethanolamine, and stearic and palmitic acids were inactive. The model lipid, mono-oleoylglycerol (250 nmol), co-precipitated with FP from a 0.09 M acetate medium at pH 5 and promoted the polymerization of 215 nmol (61%) of the ferriprotoporphyrin IX in the precipitate during a 24-h incubation at 37 degrees C. Polymerization was maximal at pH 5, it was approximately linear for 2 h, and it continued at a decreasing rate for 24 h. The polymer contained exclusively ferriprotoporphyrin IX (97+/-1.3%, mean+/-S.E., n=4) and exhibited the solubility and the electronic absorption and infrared spectral characteristics of the sequestered ferriprotoporphyrin IX of hemozoin. Detergents presumably promote polymerization in an acid medium by helping to dissolve monomeric FP. We suggest that unsaturated lipids co-precipitate with FP in the parasite's acidic food vacuole and also dissolve sufficient monomeric FP to allow polymerization.

Animals↗
PubMed2000

Preparation of non-fouling surface through the coating with core-polymerized block copolymer micelles having aldehyde-ended PEG shell.

A new type of surface modification with reactive polymeric micelle was carried out for the creation of non-fouling surface. Amphiphilic poly(ethylene glycol)-b-poly(D,L lactide) (PEG/PLA) copolymers possessing acetal group at PEG-end and methacryloyl group at PLA-end were quantitatively synthesized via an anionic polymerization technique. A micelle of narrow distribution was prepared from the block copolymer. Acetal groups on the micelle surface were quantitatively converted into aldehyde group by an acid treatment. The methacryloyl group located in the core of the micelle was polymerized via radical polymerization to form core-polymerized micelle having reactive aldehyde groups on the surface. The core-polymerized reactive micelle was coated to a primary amino-containing polypropylene (PP) plate that was prepared by a plasma treatment. A reductive amination reaction was employed for a conjugation of the reactive core-polymerized micelle on the surface via a covalent linkage. The coating was evaluated by X-ray photoelectron spectroscopy, zeta-potential measurement, and the adsorption of bovine serum albumin, and compared with the PEG-coating under the same condition. The ratio of peak from &Cmacr;&z.sbnd;O bond to C&z.sbnd;&Cmacr;&z.sbnd;C bond indicated that the density of PEG on the surface was higher for the micelle coating than the linear PEG-coating. This is also confirmed by the zeta-potential measurement. By coating the amino-PP surface with micelle, the zeta-potential was remarkably decreased while the PEG-coating under the same condition decreased only appreciably, indicating that micelle coating efficiently masked the surface charge. Further, micelle-covered surface exhibited reduction of protein adsorption. The reduction of protein adsorption along with remarkably masked surface charge implies the high applicability of the micelle coatings to biomedical and bioanalytical applications.

Journal Article↗
PubMedDate not supplied

Preliminary characterization of novel amino acid based polymeric vesicles as gene and drug delivery agents.

The amino acid homopolymers, poly-L-lysine and poly-L-ornithine, have been modified by the covalent attachment of palmitoyl and methoxypoly(ethylene glycol) (mPEG) residues to produce a new class of amphiphilic polymers-PLP and POP, respectively. These amphiphilic amino acid based polymers have been found to assemble into polymeric vesicles in the presence of cholesterol. Representatives of this new class of polymeric vesicles have been evaluated in vitro as nonviral gene delivery systems with a view to finding delivery systems that combine effective gene expression with low toxicity in vivo. In addition, the drug-carrying capacity of these polymeric vesicles was evaluated with the model drug doxorubicin. Chemical characterization of the modified polymers was carried out using (1)H NMR spectroscopy and the trinitrobenzene sulfonic acid (TNBS) assay for amino groups. The amphiphilic polymers were found to have an unreacted amino acid, palmitoyl, mPEG ratio of 11:5:1, and polymeric vesicle formation was confirmed by freeze-fracture electron microscopy and drug encapsulation studies. The resulting polymeric vesicles, by virtue of the mPEG groups, bear a near neutral zeta-potential. In vitro biological testing revealed that POP and PLP vesicle-DNA complexes are about one to 2 orders of magnitude less cytotoxic than the parent polymer-DNA complexes although more haemolytic than the parent polymer-DNA complexes. The polymeric vesicles condense DNA at a polymer:DNA weight ratio of 5:1 or greater and the polymeric vesicle-DNA complexes improved gene transfer to human tumor cell lines in comparison to the parent homopolymers despite the absence of receptor specific ligands and lysosomotropic agents such as chloroquine.

Amino Acids↗
PubMed1985

Effect of capping protein on the kinetics of actin polymerization.

Acanthamoeba capping protein increased the rate of actin polymerization from monomers with and without calcium. In the absence of calcium, capping protein also increased the critical concentration for polymerization. Various models were evaluated for their ability to predict the effect of capping protein on kinetic curves for actin polymerization under conditions where the critical concentration was not changed. Several models, which might explain the increased rate of polymerization from monomers, were tested. Two models which predicted the experimental data poorly were (1) capping protein was similar to an actin filament, bypassing nucleation, and (2) capping protein fragmented filaments. Three models in which capping protein accelerated, but did not bypass, nucleation predicted the data well. In the best one, capping protein resembled a nondissociable actin dimer. Several lines of evidence have supported the idea that capping protein blocks the barbed end of actin filaments, preventing the addition and loss of monomers [Cooper, J. A., Blum, J. D., & Pollard, T. D. (1984) J. Cell Biol. 99, 217-225; Isenberg, G. A., Aebi, U., & Pollard, T. D. (1980) Nature (London) 288, 455-459]. This mechanism was also supported here by the effect of capping protein on the kinetics of actin polymerization which was nucleated by preformed actin filaments. Low capping protein concentrations slowed nucleated polymerization, presumably because capping protein blocked elongation at barbed ends of filaments. High capping protein concentrations accelerated nucleated polymerization because of capping protein's ability to interact with monomers and accelerate nucleation.

Actin Depolymerizing Factors↗
PubMed2006

Inhibition of hemoglobin S polymerization in vitro by a novel 15-mer EF-helix beta73 histidine-containing peptide.

Our mutational studies on Hb S showed that the Hb S beta73His variant (beta6Val and beta73His) promoted polymerization, while Hb S beta73Leu (beta6Val and beta73Leu) inhibited polymerization. On the basis of these results, we speculated that EF-helix peptides containing beta73His interact with beta4Thr in Hb S and compete with Hb S, resulting in inhibition of Hb S polymerization. We, therefore, studied inhibitory effects of 15-, 11-, 7-, and 3-mer EF-helix peptides containing beta73His on Hb S polymerization. The delay time prior to Hb S polymerization increased only in the presence of the 15-mer His peptide; the higher the amount, the longer the delay time. DIC image analysis also showed that the fiber elongation rate for Hb S polymers decreased with increasing concentration of the 15-mer His peptide. In contrast, the same 15-mer peptide containing beta73Leu instead of His and peptides shorter than 11 amino acids containing beta73His including His alone showed little effect on the kinetics of polymerization and elongation of polymers. Analysis by protein-chip arrays showed that only the 15-mer beta73His peptide interacted with Hb S. CD spectra of the 15-mer beta73His peptide did not show a specific helical structure; however, computer docking analysis suggested a lower energy for interaction of Hb S with the 15-mer beta73His peptide compared to peptides containing other amino acids at this position. These results suggest that the 15-mer beta73His peptide interacts with Hb S via the beta4Thr in the betaS-globin chain in Hb S. This interaction may influence hydrogen bond interaction between beta73Asp and beta4Thr in Hb S polymers and interfere in hydrophobic interactions of beta6Val, leading to inhibition of Hb S polymerization.

Circular Dichroism↗
PubMedDate not supplied

Peroxidase-catalyzed oxidative polymerization of bisphenols.

Oxidative polymerization of bisphenolic monomers has been performed using peroxidase as catalyst in an aqueous organic solvent. Peroxidase induced the polymerization of an industrial product, bisphenol F, consisting of 2,2'-, 2,4'-, and 4,4'-dihydroxydiphenylmethanes. Under the selected conditions, the quantitative formation of the polymer was observed. Among the isomers, 2,4'- and 4,4'-dihydroxydiphenylmethanes were polymerized to give the polymer in high yields, whereas no polymerization of the 2,2'-isomer occurred. These data suggest that the radical transfer reaction between a phenoxy radical of the enzymatically polymerizable monomer and the enzymatically nonpolymerizable monomer frequently took place during the polymerization. Various 4,4'-dihydroxyphenyl compounds were also polymerized by peroxidase catalyst. The polymerization behaviors, and solubility and thermal properties of the resulting polymers strongly depended on the bridge structure as well as the enzyme origin. Polymers from dihydroxydiphenylmethanes showed relatively high thermal stability.

Catalysis↗
PubMed2001

Involvement of catalytic amino acid residues in enzyme-catalyzed polymerization for the synthesis of polyesters.

Recently, a variety of aliphatic polyesters have been synthesized using hydrolases such as lipases and PHB depolymerases, and the reaction mechanism for these enzyme-catalyzed polymerization has been discussed. In this paper, we have studied the involvement of the catalytic amino acid residues of the hydrolase in enzyme-catalyzed polymerization with an extracellular PHB depolymerase from Alcaligenes faecalis T1. A wild-type PHB depolymerase and three kinds of site-specific mutants (catalytic amino acids were substituted) were prepared and their polymerization activities for the ring-opening polymerization of (R)-beta-butyrolactone (BL) were compared. BL was polymerized at 80 degrees C in bulk by the wild-type enzyme to yield polymers consisting of cyclic and linear structures in a high monomer conversion. In contrast, none of the mutant enzymes showed obvious polymerization activity. These results have clearly demonstrated that the catalytic triad is indeed responsible for the enzyme-catalyzed polymerization of BL.

4-Butyrolactone↗
PubMedDate not supplied

Correlation between structure of the lactones and substrate specificity in enzyme-catalyzed polymerization for the synthesis of polyesters.

Small-size (4-membered) and medium-size (5-, 6-, and 7-membered) unsubstituted lactones as well as unsubstituted macrolides (12 and 13 membered) were subjected to the ring-opening polymerization using the extracellular PHB depolymerase from Alcaligenes faecalis T1 (PhaZ(Afa)). The characteristic reactivities of the lactones were discussed based on a tertiary structure model of the active site of the PhaZ(Afa). With respect to the ring-size of the lactones, the 4-membered beta-propiolactone and 6-membered delta-valerolactone (delta-VL) showed the highest polymerization activity, and delta-VL seemed to be the upper size limit for the molecular recognition of the narrow active site cleft of PhaZ(Afa). On the other hand, epsilon-caprolactone, 11-undecanolide, and 12-dodecanolide, which showed excellent polymerization activities by lipases, were scarcely polymerized by PhaZ(Afa). This was ascribed to the difference in the recognition sites between PhaZ(Afa) and lipase. In addition, the effect of the substrate-binding domain of PhaZ(Afa) and the enantioselective ring-opening polymerization of (R,S)-beta-butyrolactone ((R,S)-beta-BL) were studied. The substrate-binding domain lacking PhaZ(Afa) showed higher reactivities than PhaZ(Afa) for the polymerization of the lactones and that a significant enantioselectivity was observed at the early stage of the polymerization of (R,S)-beta-BL to produce the (R)-enriched optically active poly(3-hydroxybutyrate).

Acyltransferases↗
PubMedDate not supplied

Horseradish peroxidase-catalyzed polymerization of cardanol in the presence of redox mediators.

Horseradish peroxidase-catalyzed polymerization of cardanol in aqueous organic solvent was investigated in the presence of a redox mediator. Cardanol is a phenol derivative from a renewable resource mainly having a C15 unsaturated hydrocarbon chain with mostly 1-3 double bonds at a meta position. Unlike soybean peroxidase (SBP), it has been shown that horseradish peroxidase (HRP) is not able to perform oxidative polymerization of phenol derivatives having a bulky meta substituent such as cardanol. For the first time, redox mediators have been applied to enable horseradish peroxidase to polymerize cardanol. Veratryl alcohol, N-ethyl phenothiazine, and phenothiazine-10-propionic acid were tested as a mediator. It is surprising that the horseradish peroxidase-catalyzed polymerization of cardanol took place in the presence of N-ethyl phenothiazine or phenothiazine-10-propionic acid. However, veratryl alcohol showed no effect. FT-IR and GPC analysis of the product revealed that the structure and properties of polycardanol formed by HRP with a mediator were similar to those by SBP. This is the first work to apply a redox mediator to enzyme-catalyzed oxidative polymerization. Our new finding that oxidative polymerization of a poor substrate, which the enzyme is not active with, can take place in the presence of an appropriate mediator will present more opportunities for the application of enzyme-catalyzed polymerization.

Catalysis↗
PubMedDate not supplied

Fluorescence spectroscopy and multivariate spectral descriptor analysis for high-throughput multiparameter optimization of polymerization conditions of combinatorial 96-microreactor arrays.

Selection of optimum process conditions in combinatorial microreactors is essential if the combinatorial synthesis process is to be correlated with the synthesis process on a more conventional scale and the materials are to have the desired chemical properties. We have developed a new methodology for the high-throughput multiparameter optimization of polymerization reaction conditions in arrays of microreactors. Our strategy is based on the application of nondestructive spectroscopic techniques to measure chemical properties of polymers directly in individual microreactors followed by the multivariate spectral descriptor analysis for rapid determination of the optimal process conditions. We have demonstrated our strategy in the high-throughput multiparameter optimization of process conditions in thin-film melt polymerization reactions performed in 96-microreactor arrays for combinatorial screening of new polymerization catalysts. The combinatorial polymerization system was optimized for the best processing parameters using a set of input variables that included reactant parameters (relative amounts of starting components and catalyst loading) and processing variables (reaction time, reaction temperature, and inert gas flow rate). The measured output parameters were the chemical properties of materials and reproducibility of the material formation in replicate polymerizations in microreactors. Spatially resolved nondestructive evaluation of polymer formation was performed directly in individual microreactors and provided information about the spatial homogeneity of polymers in microreactors. It showed to be another powerful indicator of the reproducible polymerization process on the combinatorial scale. Although the methodology described here was implemented for high-throughput optimization of polymerization conditions, it is more general and can be further implemented for a variety of applications in which optimization of process parameters can be studied in situ or off-line using spectroscopic and other tools.

Journal Article↗