Uniform poly(isopropylacrylamide) gel beads for immobilization of α-chymotrypsin

In this study, α-chymotrypsin was immobilized via physical entrapment within large, uniformly spherical, and thermally reversible poly(N-isopropylacrylamide) [poly(NIPAM)] beads. The gel beads were prepared in an aqueous dispersion medium by using Ca-alginate gel as the polymerization mold. In this preparation, potassium persulfate/tetramethylethylenediamine and sodium-alginate/calcium chloride were used as the redox initiator and the stabilizer systems, respectively. Thermoresponsive poly(NIPAM) gel beads 3 mm in size and including α-chymotrypsin were produced by the proposed procedure. The use of an aqueous bead-forming medium did not cause significant enzyme leakage during the preparation of enzyme-gel beads. Michaelis–Menten kinetics was used to define the behaviors of enzyme-gel beads prepared with different enzyme loadings. The Lineweaver–Burk plot indicated that the enzyme-gel system had a reasonably higher K_m value relative to that of free enzyme due to the internal mass transfer resistance against the substrate diffusion. The enzyme-gel system exhibited the maximum activity at 30°C due to the thermoresponsive character of the carrier matrix. However, the maximum activity with the free enzyme was observed at 40°C. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 67:1127–1139, 1998     

Poly(acrylic acid)–poly(vinyl alcohol) copolymers with superabsorbent properties

Biodegradable polyacrylates were produced by a series of novel copolymerization and/or crosslinking techniques using poly(vinyl alcohol) (PVA) moieties modified by the incorporation of olefinic structures. PVA was modified by a tosylation and/or detosylation reaction. The functionalized PVA was copolymerized and/or crosslinked with acrylic acid or its partially neutralized form to give crosslinked polyacrylates that could swell in water. Their swelling behavior was determined under load. Degradation studies were performed in α-chymotrypsin, trypsin, and papain solutions. © 1998 John Wiley & Sons, Inc. J. Appl. Polym. Sci. 70: 817–829, 1998     

Synthesis of hydroxyl-capped comb-like poly(ethylene glycol) to develop shell cross-linkable micelles

A novel hydroxyl-capped comb-like poly[poly(ethylene glycol) methacrylate] (PPEGMA) was prepared via atom transfer radical polymerization (ATRP) of α-methylacryloyl-ω-hydroxyl-poly(ethylene glycol) at ambient temperature. The polymerization kinetics of the block copolymer was studied by gel permeation chromatography (GPC) and ¹H NMR. It is of interest to find the well-defined comb-like PEG can associate into micelles, which have hydrophilic PEG shell end-capped by hydroxyl groups. The hydroxyl in the shell were further cross-linked by divinyl sulfone (DVS), which could couple with two capped-end hydroxyl groups. The XPS, TEM, AFM and laser scattering particle size distribution analyzer results revealed that reactive micelles could be cross-linked by DVS. The reactive, cross-linkable micelles with PEG shell may have great potential as new drug carrier and nanoreactor, etc.     

Preparation and characterization of unsaturated poly(ester‐imide) based on 1,4‐bis[2′‐trifluoromethyl‐4′‐(4″‐glycolformate)‐trimellitimidophenoxy]benzene

A novel diimidodialcohol monomer, 1,4‐bis[2′‐trifluoromethyl‐4′‐(4″‐glycolformate)‐ trimellitimidophenoxy]benzene (BGTB), was synthesized and characterized. It was reacted with isophthalic acid, maleic anhydride and propylene glycol to produce a novel unsaturated poly(ester‐imide) (BGTB‐UPEI) with imide and trifluoromethyl groups in the polymer backbone. The BGTB‐UPEI resin was diluted with reactive monomer (styrene) to give a low‐viscous poly(ester‐imide)/styrene (BGTB‐UPEI/St) mixed solution, which was then thermally cured to yield thermosetting BGTB‐UPEI/St composite. The effect of processing parameters such as the curing temperature and curing time, reactive monomer concentration and initiator amount on the curing reaction was systematically investigated. Experimental results indicated that the thermally cured BGTB‐UPEI/St composite exhibited much better thermal, mechanical, electrical insulating properties and chemical resistance than the standard unsaturated polyester/polystyrene composite. Copyright © 2006 Society of Chemical Industry     

An Synthesepulp immobilisierte Enzyme,I.

Synthetic pulp—a polyethylene fibrid which contains poly(vinyl alcohol)—was reacted with 2-(3-aminophenyl)-1,3-dioxolane. The amino derivative was transferred into the reactive diazonium compound. The content of reactive diazonium groups was determined by reaction with tyrosine. The diazonium derivatives of synthetic pulp were used for the immobilization of the hydrolases trypsin, chymotrypsin, papain, aminoacrylase, esterase and urease of the oxidoreductases glucose oxidase, catalase, peroxidase, and glucose-6-phosphate-dehydrogenase, and of the transferase hexokinase. Furthermore soybean trypsin inhibitor was immobilized on synthetic pulp via azo coupling. The protein binding ability of the reactive carriers and the enzymatic properties of the immobilization products were investigated. The thermostability of immobilized trypsin and immobilized urease, as well as the dependence of the immobilized tryptic activity on the temperature were studied. The activities of immobilized trypsin were assayed with low molecular weight substrates as well as with high molecular weight substates. The pH-optima of immobilized chymotrypsin, papain and urease were studied and the influence of buffers on the pH-activity profiles was investigated. Hexokinase and glucose-6-phosphatedehydrogenase were co-immobilized on synthetic pulp as an example for a two enzyme system and the properties of the immobilization products were investigate.     

Comparison of the reactions of organic bromides and p-toluene sulphonates with polymeric anions

Alkyl bromides and tosylates were shown to react quantitatively with the living α-methylstyrene tetramer to yield the dialkyl adduct. Alkyl bromides also reacted with α-methylstyrene and lithium in THF to yield the dimeric adduct quantitatively, whereas only about 10% yield of this product was obtained with alkyl tosylate. This difference in behaviour was interpreted in terms of the different adsorptive powers of the two alkyl salts onto lithium metal. Aryl (phenyl) bromides and tosylates reacted with the tetramer to give only low (<5%) yields of the diaryl adduct and in both cases low molecular weight poly(α-methylstyrene) was produced. Benzene was also formed with phenyl bromide and the reaction was explained in terms of a transmetallation process. With the tosylate, the presence of phenol indicated that scission occurred at the SO₂Obond. The reactions of these reagents with α-methylstyrene and lithium in THF both yielded poly(α-methylstyrene) and phenyl bromide was quantitatively converted into biphenyl. Reactions controlled by competitive adsorption were invoked to explain these findings.     

Zwitterionic poly(carboxybetaine) microgels for enzyme (chymotrypsin) covalent immobilization with extended stability and activity

There is emerging evidence that biocompatible zwitterionic materials can prevent nonspecific interactions within protein systems and increase protein stability. Here, a zwitterionic microgel was synthesized from poly (carboxybetaine methyl methacrylate) (pCB) using an inverse emulsion, free radical polymerization reaction technique. The microgel was loaded with a model enzyme, α-chymotrypsin (ChT), using a post-fabrication loading technique. A reaction scheme was developed and studied for covalent immobilization of ChT within the microgel. Confocal laser microscopy studies showed that immobilized ChT (i-ChT) was distributed within the hydrogel. The enzyme-immobilized microgels showed excellent reusability (72% of its initial activity after 10 uses) and could undergo several freezing/drying/rehydration cycles while retaining enzymatic activity. The i-ChT activity, half-life, and conformational stability were studied at varying pH and temperatures with results compared to free ChT in buffer. ChT immobilized within pCB hydrogel showed increased enzymatic stability as observed by a 13°C increase in the temperature at which i-ChT loses activity compared to free ChT. Furthermore, enzyme half-life increased up to seven-fold for the pCB immobilized ChT, and the increased stability resulted in higher activity at elevated pH. The i-ChT was most active at pH of 8.5 and was partially active up to the pH of 10.2.     

Synthesis and biological study of some pyrrolopyridine derivatives

Quinoline dicarboxylic anhydride ( 1 ) reacted with p-aminoacetophenone to give a pyrrolopyridine derivative ( 2 ). The compound produced ( 2 ) reacted with hydrazine hydrate, hydroxyl amine hydrochloride, semicarbazide and thiosemicarbazide to produce pyrrolopyridine derivatives ( 3-6 ). Compound 3 reacted with aromatic aldehyde, PhNCS or PhNCO to produce compounds 7-9 . Compound 4 reacted with PhNCO to give the carbamate ester 10 . When compound 5 was boiled with SOC1₂, the thiadiazolo compound ( 11 ) was obtained. When compound 6 was allowed to react with α-haloesters and α-haloketones, the thiazolo compounds ( 12-14 ) were produced. All the synthesized compounds were tested against some Gram-positive and some Gram-negative bacteria and they gave satisfactory results.     

A supramolecular gene carrier composed of multiple cationic α-cyclodextrins threaded on a PPO-PEO-PPO triblock polymer

Cationic polymers have been studied as promising nonviral gene delivery vectors. In contrast to the conventional polycations with long sequences of covalently bonded repeating units, this work reports a supramolecular gene carrier where many cationic cyclic units are threaded over a polymer chain to form a chain-interlock structured gene carrier. A series of novel supramolecular cationic polyrotaxanes consisting of multiple α-cyclodextrin (α-CD) rings grafted with various linear or nonlinear oligoethylenimine (OEI) chains, which are threaded and capped over a reverse Pluronic poly(propylene oxide)-poly(ethylene oxide)-poly(propylene oxide) (PPO-PEO-PPO) amphiphilic triblock copolymer chain, were synthesized and characterized in term of their molecular and supramolecular structures, DNA binding and condensation ability, cytotoxicity, and in vitro gene transfection efficiency in cultured cells. The supramolecular cationic polyrotaxanes were found to contain 8 cationic α-CD rings that are threaded on a PPO-PEO-PPO triblock copolymer chain. They demonstrated strong ability to bind and condense plasmid DNA into nano-sized particles which are suitable for gene delivery. In both HEK293 and COS7 cells, these polyrotaxanes show low cytotoxicity and high transfection efficiency. In particular, the cationic polyrotaxanes displayed sustained gene delivery capability in HEK293 cells in both serum and serum free condition with the increasing expression duration.     

Heterocyclic quinones. VIII. Synthesis and spectra of new carbazoloquinone derivatives of naturally occurring amino acids

Fifteen naturally occurring amino acids representing basic, neutral and acidic members were interacted with 4,4′-dimethoxydiquinone (I). Basic amino acids reacted readily to give amino acid substituted carbazoloquinones (III), while neutral and acidic amino acids reacted only after addition of an acid binding agent. Using an excess of any of the amino acids resulted in the substitution of the quinonoid methoxyl group in compounds (III) by an amino acid moiety. In the case of basic amino acids, this substitution reaction was preferentially influenced by a terminal amino or guanidino amino rather than by an α-amino group. Moreover, basic amino acids could be reacted with two moles of (I) to produce dicarbazoloquinones (X). The i.r. and u.v.-visible spectra of the various carbazoloquinone products were determined and discussed.     

Modeling and Experimental Data for the Reverse Micellar Extraction of Proteins Using a New Surfactant

ABSTRACT

In this study the reverse micellar extraction of α-chymotrypsin using bis(2,4,4-trimethylpentyl) sodium dithiophosphinate as the surfactant has been investigated. Experiments were performed to determine the effects of pH and salt concentration on the reverse micellar extraction and backward extraction of α-chymotrypsin in isooctane/decanol mixtures. The results showed that both pH and salt concentration influence the reverse micellar extraction of α-chymotrypsin. The pH affects the extraction of the protein through changing the sign and number of the charges carried by protein molecules and thereby affects their interactions with the charged head groups of the surfactant molecules. It was found that at high pH values the hydrogen ions compete with positively charged protein molecules and exchange with the counterions of the surfactant molecules, and as a result destroy the reverse micelles. This effect was exploited for the backward extraction of protein molecules from the reverse micellar phase. A model has been developed to correlate the experimental data of reverse micellar extraction of proteins. In the model the reverse micelles were treated as noninteractive ion-exchange sites. The activity coefficient of the protein molecules in reverse micelles was represented by the model proposed by Pitzer. It has been shown that the model can correlate the experimental data obtained in this work and those reported in other studies.     

Biodegradable polymers: Chymotrypsin degradation of a low molecular weight poly(ester-urea) containing phenylalanine

A low molecular weight poly(ester urea), poly(L-phenylalanine/ethylene glycol/1,6-diisocyanatohexane), and a model diester diurea, dimethyldiphenylalaninehexamethylenediruea, were synthesized and found to be hydrolyzed by α-chymotrypsin solutions at pH 7.8. After ten-day exposure to 0.1 mg/ml enzyme solution at room temperature, 79.9% weight loss was observed for the model diester diurea (containing two ester linkages per molecule). A weight loss of 19.4% was observed for the poly(ester urea) of M?_n 1930 (containing an average of eight ester linkages per molecule) after the same period of exposure. A poly(ester urea) of similar molecular weight, but derived from glycine instead of phenylalanine, was found to resist chymotrypsin hydrolysis.     

Antifeedant and Phytotoxic Activity of the Sesquiterpene <Emphasis Type="Italic">p</Emphasis>-Benzoquinone Perezone and Some of its Derivatives

The sesquiterpene p-benzoquinone perezone (1), isolated from Perezia adnata var. alamani (Asteraceae), and its non-natural derivatives isoperezone (2), dihydroperezone (3), dihydroisoperezone (4), and anilidoperezone (5) were tested as antifeedants against the herbivorous insects Spodoptera littoralis, Leptinotarsa decemlineata, and Myzus persicae. Compounds 1-5 exhibited strong antifeedant activity against L. decemlineata and M. persicae, and elicited a low response by S. littoralis. Antifeedant activity on L. decemlineata and M. persicae increased when the hydroxyl group at C-3 in perezone (1) was changed to C-6 to give isoperezone (2). The same effect was found with hydrogenation of the double bond of the alkyl chain of (1) to yield dihydroperezone (3). In contrast, hydrogenation of this double bond in isoperezone (2) to give dihydroisoperezone (4) led to a reduction in antifeedant activity. Determination of the phytotoxic activity of 1-5 revealed that 3 had a significant inhibition effect on Lactuca sativa radicle length growth.     

铜与聚4-乙烯基吡啶的络合物催化漆酚氧化聚合

铜与聚4—乙烯基吡啶的络合物对漆酚的氧化聚合具有明豆的催化活性,在二甲苯中可以作为多相催化剂重复使用。铜、锰双金属的聚4—乙烯吡啶的络合物的催化活性比纯粹铜的络合物好,催化剂中 Mn/Cu 摩尔此约为1.2时较佳。这些催化剂催化所得产物由于仍有低分子量的漆酚存在,直接涂膜干燥慢。除去低分子量漆酚后的漆液涂膜,干燥快,颜色浅,物理性能优异.     

N-(2,6-二甲苯基)-N-酰基丙氨酸甲酯类化合物的合成及生物活性研究

以α-氯丙酸为起始原料,甲酯化后得α-氯丙酸甲酯;在碘化钾催化下,α-氯丙酸甲酯与2,6-二甲基苯胺缩合获得中间体N-(2,6-二甲苯基)丙氨酸甲酯,再在室温下以吡啶作缚酸剂,与系列羧酸酰氯反应15 h,合成了12个新型N-(2,6-二甲苯基)-N-酰基丙氨酸甲酯类目标化合物。目标化合物的结构经GC-MS、FTIR和元素分析确认。对目标化合物进行了杀菌、杀虫、除草生物活性测定,结果表明,各化合物均具有不同程度的杀菌生物活性。     

Biodegradable self-reporting nanocomposite films of poly(lactic acid) nanoparticles engineered by layer-by-layer assembly

We designed and fabricated multilayer assemblies of biodegradable poly(lactic acid) (PLA) nanoparticles based on hydrogen-bonding or electrostatic interactions. The PLA nanoparticles were prepared by precipitation method and their surface charge was switched by modified precipitation in the presence of poly(ethylene imine) (PEI). Moreover, gold nanoparticles were grown within the PLA nanoparticle assemblies either through UV-irradiation or under mild reducing conditions to create biodegradable nanocomposites with distinct optical response which allows monitoring biodegradation of the films. The nanocomposite coatings of PLA nanoparticles were enzymatically degraded by α-chymotrypsin. We demonstrated that the biodegradation process can be colorimetrically monitored with UV-vis spectroscopy thus opening the way for facile and real-time monitoring useful for biotechnology applications.     

乙氧羰基烯丙基取代的肟醚类化合物的研究

采用"一锅法"来研究这一反应。由酮肟1与氢化钠作用产生酮肟阴离子2,酮肟阴离子再与α-乙氧羰基乙烯基膦酸二乙酯3作用产生膦酸酯取代的碳负离子4,该碳负离子进一步与醛作用得到α-乙氧羰基烯丙基肟醚化合物,产率在73%～79%。     

Mercuriation and thalliation of polymers prepared using 2-vinylthiophene: Conversion of products into polymers containing thienylboronic acid residues

2-Vinylthiophene was homopolymerised and copolymerised with styrene and/or divinylbenzene using benzoyl peroxide as the initiator. The various polymeric products reacted smoothly with mercury(II) acetate or trifluoroacetate in tetrahydrofuran to give mercuriated polymers. Several of the polymers were treated with thallium(iii) trifluoroacetate in methylene chloride but the only polymer that was satisfactorily thalliated was the linear homopolymer, poly(vinylthiophene). Several of the mercuriated polymers were reacted with iodine to give polymers containing iodothiophene residues. Examples of mercuriated and thalliated polymers were reacted with borane to give polymer-supported organ-oboranes which, on treatment with water, gave polymers containing thienylboronic acid residues. It has been demonstrated that the latter polymers can serve as polymer-supported protecting groups for diols.     

大孔载体制备及其固定化脂肪酶

以甲基丙烯酸缩水甘油酯(GMA)为单体;二乙烯基苯(DVB)为交联剂;采用固液联合致孔的方式;通过本体聚合制备具有超大孔的含有环氧基团的多孔载体。其孔径分布为典型的双孔分布;其中150～400 nm的孔区约占总孔容的60%;孔隙率为59.82%;比表面积29.60 m·g-1。载体的环氧基团水解成羟基后;以戊二醛为偶联剂固定化脂肪酶。在相同条件下;比较了不同孔结构载体的固定化假丝酵母脂肪酶催化橄榄油水解的效果。结果表明;具有一定超大孔结构的多孔载体固定化酶的效果最好。同时考察了固定化脂肪酶在正己烷中催化十二酸辛醇的酯化反应活力。     

Synthesis of Hyperbranched Polypropylene/Organoclay Nanocomposites by Metal Catalyzed Living Radical Polymerization and Solvent Blending Method

Isotactic polypropylene-based polymer hybrids linking poly methyl methacrylate was successfully synthesized by a graft copolymerization from maleic anhydride-modified polypropylene (MAH-graft-PP). MAH-graft-PP reacted with ethanolamine to produce a hydroxyl group containing polypropylene (PP-OH) and obtained PP-OH was treated with α-phenyl chloroacetyl chloride and converted to a chloroacetyl group containing polypropylene (PP-Cl). The metal-catalyzed radical polymerization of MMA with PP-Cl was performed using a copper catalyst system in xylene solution at 100°C to give the PP-based polymer hybrids linking PMMA segments (PMMA-graft-MAH-graft-PP). Finally the grafted copolymer/MMt nanocomposite prepared by solution intercalation method.