Home About us Contact
|
Home About us Contact | ||
|
|
||
Enzymatic Polymerization (enzymatic + polymerization)
Selected AbstractsSynthesis of Fluorinated Chitin Derivatives via Enzymatic PolymerizationMACROMOLECULAR BIOSCIENCE, Issue 10 2006Akira Makino Abstract Summary: Synthesis of fluorinated chitin derivatives has been achieved using chitinase from Bacillus sp. as a catalyst. 6,-Fluoro- (1a), 6-fluoro- (1b) and 6,6,-difluoro- (1c) chitobiose oxazoline derivatives were newly prepared as TSAS monomers for chitinase. Ring-opening polyaddition of these monomers proceeded effectively at pH 8.0,9.0 and 30,40,°C, giving rise to alternatingly 6-fluorinated chitin derivatives (2a and 2b) from 1a and 1b, and fully 6-fluorinated chitin derivative (2c) from 1c under total control of regioselectivity and stereochemistry. XRD measurements revealed that polysaccharides 2a and 2b had crystalline structures similar to that of , -chitin. [source] Cyclodextrins in Polymer Synthesis: Enzymatic Polymerization of a 2,6-Dimethyl- , -Cyclodextrin/2,4-Dihydroxyphenyl-4,-Hydroxybenzylketone Host-Guest Complex Catalyzed by Horseradish Peroxidase (HRP)MACROMOLECULAR BIOSCIENCE, Issue 8 2003Lorenzo Mejias Abstract This paper reports the enzymatic polymerization of the inclusion complex 2,4-dihydroxyphenyl-4,-hydroxybenzylketone/2,6-dimethyl- , -cyclodextrin by horseradish peroxidase (HRP) in aqueous media. The structure of the complex was determined by means of NOESY-NMR and crystallographic analysis (indicating an orthorhombic structure). The enzymatic polymerization of the uncomplexed 2,4-dihydroxyphenyl-4,-hydroxybenzylketone yields oligomers with molecular weights up to in organic-aqueous media, but because of its poor solubility in aqueous systems, no polymerization is observed if water is used as solvent. An increase of the availability of the ketone in solution is achieved by complexing it with random-methylated , -cyclodextrin in water. We found that the use of methylated , -cyclodextrin in equimolar concentration to the monomer increases the polymerization yield and the average molecular weight. The polymers formed were analyzed by GPC and ATR-FTIR techniques. Representation from X-ray diffraction analysis of the 2,6-dimethyl- , -cyclodextrin/2,4-dihydroxyphenyl-4,-hydroxybenzylketone host-guest complex (3). [source] Biodegradable Poly(ester hydrazide)s via Enzymatic PolymerizationMACROMOLECULAR RAPID COMMUNICATIONS, Issue 16 2005Guillaume Métral Abstract Summary: The reaction of hydrazine with ethyl glycolate results in 1,2-bisglycoylhydrazine, a monomer that was used for the lipase-catalyzed synthesis of biodegradable poly(ester hydrazide)s. The polymers derived from the hydrazide-containing monomer and vinyl-activated adipic, suberic, and sebacic acid, respectively, showed low melting temperatures of 136 to 141,°C and are thermally stable up to 300,°C. The aliphatic poly(ester hydrazide)s (PEHs) are highly crystalline, as proven by polarization microscopy and atomic force microscopy. Further, the PEHs represent the first described biodegradable poly(hydrazide)s. They degrade in the presence of lipase at 37,°C within a few weeks. Synthetic route to poly(ester hydrazide)s. [source] From polymeric particles to multifunctional nanocapsules for biomedical applications using the miniemulsion processJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 3 2010Katharina Landfester Abstract The miniemulsions process represents a versatile tool for the formation of polymeric nanoparticles consisting of different kinds of polymer as obtained by a variety of polymerization types ranging from radical, anionic, cationic, enzymatic polymerization to polyaddition, and polycondensation. The process perfectly allows the encapsulation of hydrophilic and hydrophobic liquids and solids in polymeric shells, molecularly dissolved dyes or other components. In combination with a specific functionalization of the nanoparticles' or nanocapsules' surfaces and the possibility to release substances in a defined way from the interior, complex nanoparticles or nanocapsules are obtained, which are ideally suited for application in biomedical application as marker and targeted drug-delivery system. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 493,515, 2010 [source] Challenge of synthetic celluloseJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 4 2005Shiro Kobayashi Abstract This article focuses on why and how the chemical synthesis of cellulose was accomplished. The synthesis of cellulose was an important, challenging problem for half a century in polymer chemistry. For the synthesis, a new method of enzymatic polymerization was developed. A monomer of ,- D -cellobiosyl fluoride (,-CF) was designed and subjected to cellulase catalysis, which led to synthetic cellulose for the first time. Cellulase is a hydrolysis enzyme of cellulose; cellulase, inherently catalyzing the bond cleavage of cellulose in vivo, catalyzes the bond formation via the polycondensation of ,-CF in vitro. It is thought that the polymerization and hydrolysis involve a common intermediate (transition state). This view led us to a new concept, a transition-state analogue substrate, for the design of the monomer. The preparation of cellulase proteins with biotechnology revealed the enzymatic catalytic functions in the hydrolysis and polymerization to cellulose. High-order molecular structures were in situ formed and observed as fibrils (cellulose I) and spherulites (cellulose II). In situ small-angle neutron scattering measurements suggested a fractal surface formation of a synthetic cellulose assembly. The principle of cellulose synthesis was extended to the synthesis of other natural polysaccharides, such as xylan and amylose, and unnatural polysaccharides. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 693,710, 2005 [source] Cyclodextrins in Polymer Synthesis: Enzymatic Polymerization of a 2,6-Dimethyl- , -Cyclodextrin/2,4-Dihydroxyphenyl-4,-Hydroxybenzylketone Host-Guest Complex Catalyzed by Horseradish Peroxidase (HRP)MACROMOLECULAR BIOSCIENCE, Issue 8 2003Lorenzo Mejias Abstract This paper reports the enzymatic polymerization of the inclusion complex 2,4-dihydroxyphenyl-4,-hydroxybenzylketone/2,6-dimethyl- , -cyclodextrin by horseradish peroxidase (HRP) in aqueous media. The structure of the complex was determined by means of NOESY-NMR and crystallographic analysis (indicating an orthorhombic structure). The enzymatic polymerization of the uncomplexed 2,4-dihydroxyphenyl-4,-hydroxybenzylketone yields oligomers with molecular weights up to in organic-aqueous media, but because of its poor solubility in aqueous systems, no polymerization is observed if water is used as solvent. An increase of the availability of the ketone in solution is achieved by complexing it with random-methylated , -cyclodextrin in water. We found that the use of methylated , -cyclodextrin in equimolar concentration to the monomer increases the polymerization yield and the average molecular weight. The polymers formed were analyzed by GPC and ATR-FTIR techniques. Representation from X-ray diffraction analysis of the 2,6-dimethyl- , -cyclodextrin/2,4-dihydroxyphenyl-4,-hydroxybenzylketone host-guest complex (3). [source] Chemoenzymatic Synthesis of Amylose-Grafted ChitosanMACROMOLECULAR RAPID COMMUNICATIONS, Issue 7 2007Shun-ichi Matsuda Abstract An amylose-grafted chitosan has been synthesized by a chemoenzymatic method according to the following two reactions. First, maltoheptaose is introduced to chitosan by a reductive amination using sodium cyanotrihydroborate in a mixed solvent of 1.0 mol,·,L,1 aqueous acetic acid and methanol at room temperature to produce a maltoheptaose-grafted chitosan that has a well-defined molecular structure. A phosphorylase-catalyzed enzymatic polymerization of , - D -glucose 1-phosphate is then performed from the maltoheptaose-grafted chitosan to obtain the amylose-grafted chitosan. This material does not dissolve in any solvent, e.g., aqueous acetic acid and dimethyl sufoxide, which are good solvents for chitosan and amylose, respectively. [source] | ||||||||||