巨大芽胞杆菌环氧水解酶的固定化及其催化性能

考察了多种载体对巨大芽孢杆菌ECU1001环氧水解酶的固定化.以大孔DEAE-纤维素离子交换树脂为载体时,固定化酶的活力回收达70%.进一步考察了温度和pH对固定化酶活力的影响,并使用该固定化酶进行了缩水甘油苯基醚对映选择性水解批次反应.结果表明,在较低的底物浓度下该固定化酶的稳定性较好,10批反应后仍然剩余72.4%的活力.     

用巨大芽孢杆菌ECU1001环氧水解酶在有机-水两相系统中高效生产(S)-缩水甘油苯基醚

 为克服环氧化物缩水甘油苯基醚在水中的溶解度低和自发水解，本文建立了异辛烷-水两相反应体系。与单一水相相比，对映体选择率从(E)从39.5提高到94.0，平均生产率从18.8 mg GPE/h/g biocatalyst提高到48.9 mg GPE/h/g biocatalyst。成功运行了搅拌式反应器，在90.1 g/L的底物浓度下，得到了光学纯的(S)-缩水甘油苯基醚 (对映体过量值达到100%, 理论收率为 44.5%)     

二茂钛/锡/环氧化合物引发苯乙烯活性自由基聚合的研究

采用单茂钛CpTiCl3和二茂钛金属化合物(n-BuCp)2TiCl2,引发剂4-甲氧苯基缩水甘油基醚(I1),1,4-丁二醇二缩水甘油基醚(I2),4,4′-亚甲基二(N,N-二缩水甘油基苯胺)(I4)和苯基缩水甘油基醚甲醛共聚物(I5)及还原剂Sn组成引发体系,引发苯乙烯活性自由基聚合,合成线型和多臂聚合物.探讨了不同茂钛金属化合物、引发剂和还原剂对苯乙烯聚合的影响;并采用13C-NMR和GPC对聚苯乙烯的结构和性能进行了表征.结果表明所得聚合物是无规聚苯乙烯,聚合物分子量高,分子量分布窄.聚合行为属于活性自由基聚合.     

环氧基修饰周期性介孔有机氧化硅对漆酶的固定化作用

以三嵌段共聚物P123为模板剂, 在酸性条件下通过1,2-三乙氧基硅基乙烷(BTESE)和3-含氧缩水甘油基-丙基-三甲氧基硅烷(GPTMS)共水解缩聚合成环氧基修饰的周期性介孔氧化硅(PMOs), 以修饰后的PMOs为载体对漆酶进行固定化, 研究了环氧基修饰对固定化酶稳定性的影响. 通过XRD、TEM、固态NMR和N₂吸附等手段表征材料的修饰效果、孔结构以及漆酶的固定化. 结果表明, 修饰后的材料保持良好的孔结构, 环氧基的修饰有利于提高固定化酶的活力, 基于环氧基修饰PMOs的固定化酶具有较高稳定性.     

有机溶剂/缓冲液双相体系中绿豆环氧化物水解酶催化环氧苯乙烯不对称水解反应

研究了有机溶剂/缓冲液双相体系中绿豆环氧化物水解酶高立体选择性地催化外消旋环氧苯乙烯水解生成(R)-苯基乙二醇反应.结果表明,与单水相反应体系相比,有机溶剂/缓冲液双相反应体系不仅有效地抑制环氧苯乙烯的非酶水解反应,而且明显提高底物的浓度,产物的收率和ee值更高.在所考察的不同有机溶剂中,正己烷不仅能较好地溶解底物,而...     

环氧水解酶在不对称合成中的应用

环氧水解酶是一种普遍存在于生物体内的酶,它能选择性水解环氧生成相应的手性二醇。这种酶在催化反应中通常显示出十分高的对映立体选择性,生成高光学活性的环氧和二醇。近年来国际上采用微生物来源的环氧水解酶对环氧底物进行不对称水解,然后再通过酸处理未开环的环氧化物“一锅法”高产率、高选择性的生成单一构型的手性二醇。这一新发展为这种酶在精细合成工业上的运用开辟了广阔的前景。     

环氧化合物水解酶的研究进展

环氧化合物水解酶(Epoxidehydrolase,EHs,EC3.3.2.3),是一组催化环氧化合物水解为相应邻位二醇的酶类,在哺乳动物、植物、昆虫和微生物体内广泛存在.由于环氧化合物的环氧乙烷部分是一个亲电的三元环,其C-O键的极性很强,能与体内包括DNA和蛋白质在内的多种活性物质发生反应,具有较强的毒性,甚至致癌性.研究表明,有两种酶涉及到环氧化合物的脱毒过程,其一为谷胱甘肽转移酶,该酶是一种广谱性脱毒酶,具有清除自由基的功能,但目前仅发现少数来源细菌的谷胱甘肽转移酶能降解模式环氧化合物;其二为环氧化合物水解酶,该酶能选择性地降解体…     

硫磺固化液体丁腈橡胶/环氧树脂体系机理和网络结构的研究

通过对比研究硫磺固化液体丁腈橡胶、液体丁腈橡胶/苯基缩水甘油醚、液体丁腈橡胶/邻烯丙基苯基缩水甘油醚3个体系的固化反应,推测了硫磺/含双键橡胶/环氧树脂体系的反应机理.采用示差扫描量热(DSC)法、红外光谱(FTIR)法、X射线光电子能谱(XPS)法、动态力学分析(DMA)法研究了固化反应放热,双键和环氧基团随反应时间的变化,固化产物中苯环、氧元素、网络结构与模型化合物结构的关系.实验结果表明,硫磺/液体丁腈橡胶体系是一步反应、硫磺/液体丁腈橡胶/环氧化合物体系是两步反应,且丁腈橡胶与环氧化合物之间有化学键键接;液体丁腈橡胶/硫磺、液体丁腈橡胶/苯基缩水甘油醚/硫磺、液体丁腈橡胶/邻烯丙基苯基缩水甘油醚/硫磺3个体系的玻璃化转变温度依次升高,储能模量、交联密度依次降低.在此基础上提出液体橡胶与环氧化合物的固化反应机理为:硫磺裂解生成硫自由基,一方面部分硫自由基与体系中的双键发生加成反应,另一方面硫自由基与烯丙基α位的活泼氢反应生成巯基,巯基引发环氧基团发生开环反应,体系内的自由基间相互偶合交联.     

分光光度法测定环氧化物浓度与环氧化物水解酶活性

研究了在弱碱性条件下 ,利用环氧化物与 4- (对硝基 )苄基吡啶之间的显色反应测定环氧化物含量 ,进而计算环氧化物水解酶活性的分光光度法。对于缩水甘油苯基醚 ,其最低检出浓度为 4.5 μmol/L,所生成染料的摩尔吸光系数 ε为 2 .2 0× 1 0 3L· mol- 1· cm- 1。在 4.5～ 30 0 μmol/L的浓度范围内 ,测量的精密度可达 0 .9%。     

原子转移自由基聚合制备聚(丙二醇-g-苯乙烯)

以氯甲基化苯氧基聚丙二醇 (CMPOPPG)为大分子引发剂 ,由CuCl/bpy催化的苯乙烯原子转移自由基聚合反应合成了聚 (丙二醇 g 苯乙烯 ) .CMPOPPG经环氧丙烷 (PO)与缩水甘油苯基醚 (GPE)的开环聚合和氯甲基化反应制得 .接枝聚合反应具有可控性 .用1H NMR和微库仑分析法对接枝共聚物进行了表征 .结果表明 ,支链分子量可控 ,接枝率可达 8.6.     

用新分离的巨大芽孢杆菌对映选择性水解缩水甘油苯基醚

Microbial epoxide hydrolases from bacterial and fungal sources?1? are hi ghly versatile catalysts for the asymmetric hydrolysis of chiral epoxides which are extensively employed as useful building blocks for the synthesis of various biologically active products in the pharmaceutical and agrochemical industries. Microorganism means allows an unlimited supply of these enzymes for preparative -scale applications. Phenyl glycidyl ether (PGE), an aryl epoxide, is a potenti ally useful compound in the synthesis of chiral amino alcohols and bioactive com pounds such as ?blockers. No suitable biocatalyst with sufficiently high enan tioselectivity (E?20) for the kinetic resolution of this compound was previ ously found among bacteria and fungi. This prompted us to screen epoxide hydrola se-producing microorganisms with higher enantioselectivity toward phenyl glycid yl ether from soil samples.     

Influence of solvent on conformational equilibrium in phenyl glycidyl ether

The conformational equilibrium in phenyl glycidyl ether in aprotic solvents was studied by the PMR method over a broad range of changes in the values of the dielectric constant. It was shown that the parameters of the multiplet of noncyclic methylene protons in the PMR spectrum of phenyl glycidyl ether are a sensitive indicator of the position of the conformational equilibrium in the glycidyl fragment. The specific interaction of the molecules of aromatic solvents with the epoxide ring has been discovered.Translated from Teoreticheskaya i Eksperimental'naya Khimiya, Vol. 21, No. 2, pp. 245–247, March–April, 1985.     

Kinetics of Photocationically Curable Formulations Involving Glycerol Diglycidyl Ether and Phenyl Glycidyl Ether

Kinetic analysis of formulations based on glycerol diglycidyl ether and phenyl glycidyl ether were carried out in the presence of sulfonium salt as initiator at 35 mW cm^?2using photo differential scanning calorimeter and the final conversion was found to increase with an increase in phenyl glycidyl ether content. The effects of formulation monomer ratios at three different temperatures were studied. The variations in the observed kinetic parameters can be related to increase in mobility of reactive species with temperature, distance of counter ion from the propagating cationic center, as well as extent of crosslinking reaction which controlled the course and duration of the reaction. The applicability of autocatalytic kinetic model was also evaluated and the system underwent early gelation and the activation energy decreased with an increase in phenyl glycidyl ether content. Analysis of stable photocured films containing glycerol diglycidyl ether and phenyl glycidyl ether showed better thermal stability than rigid films obtained with glycerol diglycidyl ether.     

Enantioselectivities of yeast epoxide hydrolases for 1,2-epoxides

Kinetic resolution of homologous series of unbranched 1,2-epoxyalkanes (C-4 to C-12), 1,2-epoxyalkenes (C-4, C-6 and C-8), a 2,2-dialkylsubstituted epoxide (2-methyl-1,2-epoxyheptane) and a benzyloxy-substituted epoxide (benzyl glycidyl ether) was investigated using resting cells of 10 different yeast strains. Biocatalysts with excellent enantioselectivity (E>100) and high initial reaction rates (>300 nmol/min/mg dry weight) were found for the 2-monosubstituted aliphatic epoxides C-6 to C-8. Yeast strains belonging to the genera Rhodotorula, Rhodosporidium and Trichosporon all preferentially hydrolyzed (R)-1,2-epoxides with retention of configuration. The epoxide hydrolases of all the yeast strains are membrane-associated.     

Enhancing the enantioselectivity of an epoxide hydrolase by directed evolution

[reaction: see text] The epoxide hydrolase (EH) from Aspergillus niger, which shows a selectivity factor of only E = 4.6 in the hydrolytic kinetic resolution of glycidyl phenyl ether, has been subjected to directed evolution for the purpose of enhancing enantioselectivity. After only one round of error-prone polymerase chain reaction (epPCR), enantioselectivity was more than doubled (E = 10.8). The improved mutant enzyme contains three amino acid exchanges, two of which are spatially far from the catalytically active center.     

Surface modification of polymers. III. Grafting of stabilizers onto polymer films

Polypropylene, polystyrene, and polyethylene have been grafted with glycidyl acrylate and glycidyl methacrylate. After 5 min of grafting with UV irradiation, polystyrene was extensively grafted to 91% coverage of glycidyl acrylate according to ESCA, while polypropylene was grafted to only 50% coverage. With glycidyl acrylate the grafting depth is estimated to be 0.1 μm for PP and 0.23 μm for PS. Glycidyl methacrylate is grafted in a thinner layer than glycidyl acrylate. The stabilizers 2,4-dihydroxybenzophenone, phenyl 4-aminosalicylate, and 4-amino-2,2,6,6-tetramethylpiperidine were attached to LDPE surfaces containing grafted glycidyl acrylate by opening of the epoxide bond. The reaction between epoxide and stabilizer is diffusion controlled at high concentrations of stabilizer. UV spectroscopy on an LDPE film grafted and reacted with 2,4-dihydroxybenzophenone showed that 227 nmol stabilizer/cm² was bound to the surface.     

Role of cyclic dithiocarbonate as a promoter in the reaction of epoxide and imine in the presence of water

It was demonstrated that the reaction of epoxide and imine as a latent initiator under highly humid conditions was accelerated by addition of 5‐phenoxymethyl‐1,3‐oxathiolane‐2‐thione ( 1 ). When 1 was added to a mixture of glycidyl phenyl ether and an imine, the reaction of the epoxide with an amine released from the imine became faster than was the case without 1 , that is, 1 worked as a promoter of the reaction. The curing rate and initial adhesive strength of epoxy resin increased compared with that without 1 . © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 4276–4283, 2004     

Reaction of glycidyl phenyl ether with imines: A model study of latent hardeners of epoxy resins in the presence of water

The hydrolyses of several imines and their reactions with glycidyl phenyl ether were examined under highly humid conditions as a model study for the development of water‐initiated hardeners for epoxy resins. Diethyl ketone‐based imines were hydrolyzed more efficiently than methyl isobutyl ketone‐based imines. The reactions of glycidyl phenyl ether with the imines depended on their hydrolysis rates and the basicity of the amines generated from them. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 971–975, 2002     

Catalytic activity of salenCo(III)OAc complex in the reaction of addition of carboxylic acids to terminal epoxides

The catalytic activity and regioselectivity were studied of the salenCo(III)OAc complex in the reaction of addition of aliphatic carboxylic acids to a series of terminal epoxides (epichlorohydrin, 1,2-epoxybutane, propylene oxide, tert-butyl glycidyl ether and 2,3-epoxypropyl phenyl ether). The reduction in the activity in the order: acetic > acrylic > methacrylic acid was found. The regioselectivity of the addition was independent on carboxylic acid nature and depended on the nature of the epoxide. The best regioselectivity for the addition to epichlorohydrin was observed. The catalytic activity and regioselectivity of salenCo(III)OAc were compared with those for chromium(III) acetate catalyst.     

Reaction of phenyl glycidyl ether with N-trimethylsilylaniline and trimethylsiloxybenzene

Conclusions It was shown by the IR spectroscopy method that the reaction of phenyl glycidyl ether with trimethylsiloxybenzene and N-trimethylsilylaniline proceeds via insertion of the opened epoxide ring between the Si-O and Si-N atoms.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 2, pp. 454–458, February, 1978.