尿苷二磷酸糖固定化酶合成法研究

利用生物酶进行体外催化反应合成不同种类的尿苷二磷酸糖（uridine diphosphate sugar,UDP-糖）,生物酶的重复利用率较低。为提高尿苷二磷酸糖的合成效率及增加产物种类,以镍螯合聚丙烯酸酯树脂为载体,对带有HIS标签的N-乙酰己糖胺激酶（N-acetylhexosamine kinase,NahK）和尿苷转移酶（uridine transferase,GlmU）进行固定化。以固定化NahK和固定化GlmU为催化酶,不同单糖作为底物,研究尿苷二磷酸糖的一锅法合成情况。利用Q柱对产物进行纯化,通过高效液相色谱法、质谱法、核磁共振氢谱法对反应产物进行检测。确定了镍螯合聚丙烯酸酯树脂对游离NahK和GlmU的实际载量分别为10和20 mg·g^-1。固定化酶量的最优配比为5.5 g固定化NahK和2.5 g固定化GlmU。固定化酶的最适pH和温度分别为8.0和35℃,且能在重复反应中稳定反应5个批次。葡萄糖、N-乙酰氨基葡萄糖和甘露糖可以参与一锅法反应,生成UDP-糖的相对分子质量分别为566、607、566,而葡萄糖醛酸、半乳糖和果糖在该体系下不能合成相应的UDP-糖。基于固定化酶技术,一锅法可合成UDP-葡萄糖、UDP-N-乙酰氨基葡萄糖、UDP-甘露糖。     

四元共聚丙烯酸酯热熔压敏胶膜的合成研究

以丙烯酸-2-乙基己酯(2-EHA)、甲基丙烯酸甲酯(MMA)、丙烯腈(AN)和丙烯酰胺(AM)为共聚单体,采用预乳化法制备聚丙烯酸酯热熔胶,研究了单体质量分数配比,乳化剂质量分数、配比及乳化方式,引发剂质量分数,温度和滴加速度对反应及性能的影响。结果表明:2-EHA 50%,MMA 40%,AN 5%,AM 5%,复合乳化剂3.0%,引发剂过硫酸钾0.3%,80～85℃,反应4 h,丙烯酸酯橡胶分子量在10万以上时,制得的热熔压敏胶膜综合性能良好。     

化橘红黄酮类化合物抑制亚硝化反应活性研究

根据超声波最佳提取工艺条件提取得到化橘红总黄酮,经乙酸乙酯萃取分为酯溶性和水溶性两部分,比较它们对亚硝化反应的抑制作用,并分别采用硅胶柱层析对酯溶性成分分离纯化,采用大孔吸附树脂法对水溶性成分进行分离纯化,得到4个主要的黄酮类化合物,研究它们对亚硝化反应的抑制作用,以期得到抑制亚硝化活性较强的化合物。结果表明化橘红总黄酮提取率可达26.42%,酯溶性和水溶性部分均能阻断亚硝胺的合成及清除亚硝酸盐,其中水溶性黄酮提取物作用较强,分离得到的4个黄酮类化合物中柚皮苷的抑制作用较强,对亚硝胺的合成的最大阻断率可达94.7%,对亚硝酸盐的最大清除率可达92.3%。     

微生物环氧化合物水解酶在有机合成中的应用*

环氧化合物水解酶是一种在自然界广泛存在的水解酶,它能高对映体选择性、高区域选择性地将环氧化合物水解为相应的邻位二醇。近年来,国际上利用微生物环氧化合物水解酶催化的不对称水解反应获得了高光学纯度环氧化合物和邻二醇,可用于多种精细化学品和生物活性物质的合成,为该酶在合成工业上的应用开辟了一条新途径。这里综述了该酶的来源、催化机理、催化特性和应用研究情况。     

脂酶催化的羧酸过氧化反应及其应用

脂酶除了催化经典的酯水解及酯化反应外,还能催化脂肪酸的过氧化。过氧脂肪酸也可以进行常规的Prileshajev环氧化。当不饱和脂肪酸参与反应时,就发生不饱和脂肪酸的自身环氧化而形成环氧脂肪酸。这个反应为脂酶的应用开辟了一个崭新的领域。     

天然产物(+)-Balasubramide的合成北大核心CSCD

以肉桂醛为起始原料,经一锅法不对称环氧化、酯胺缩合和分子内环合三步反应,不对称合成天然产物(+)-balasubramide,总收率为44%,ee值为>99%。其结构经1H NMR、13C NMR、HR-MS和IR确证。本化学合成方法简单,产率较高,为进一步研究该天然产物的生物活性及构效关系奠定一定基础。     

菜子油酸的环氧化研究

以732型强酸性阳离子交换树脂作催化剂,对菜子油酸的环氧化反应作了研究,考察了反应温度、H_2O_2浓度、催化剂用量、不同有机酸及DBP有机介质对环氧化的影响.研究结果表明:较适宜的反应温度为50℃,催化剂用量为菜子油酸重量的10%～15%,所使用H_2O_2的浓度应高于30%.在DBP的保护下,产物最高环氧值可达3.3%.     

魔芋接枝丙烯酸高吸水性树脂的制备及性能研究

本实验以魔芋精粉为基体,环己烷为连续相,Span-60为分散剂,硝酸铈铵为引发剂、用反相悬浮聚合法合成魔芋-丙烯酸高吸水性树脂。研究了多种因素对接枝共聚物吸水性能的影响。结果表明:反应时间为2 h、魔芋精粉与丙烯酸质量比为1∶5、交联剂用量为物料质量的0.04%、引发剂为3×10-3mol/L、丙烯酸中和度为60%、反应温度为70℃时,接枝共聚物吸水性能最优。并通过对接枝产物的红外图谱分析,证实了反应的可行性。     

酶促拆分丁酸环氧丙酯反应体系的筛选

利用脂肪酶对外消旋丁酸环氧丙酯进行了立体选择性的酯水解反应,考察了水解反应体系对拆分反应的影响。实验结果表明：在该水解反应中添加适量正己烷有利于拆分反应的进行;反应体系中正己烷与缓冲液的最适体积比为1：1;磷酸盐缓冲液(pH7．6)的最适离子强度为0.03mmol／L。在最适反应条件下,当该酶促拆分反应的转化率为60.6％,(R)-丁酸环氧丙酯的光学纯度可以达到93．3％。     

天然产物(+)-Balasubramide的合成

以肉桂醛为起始原料,经一锅法不对称环氧化、酯胺缩合和分子内环合三步反应,不对称合成天然产物(+)-balasubramide,总收率为44%,ee值为99%。其结构经1H NMR、13C NMR、HR-MS和IR确证。本化学合成方法简单,产率较高,为进一步研究该天然产物的生物活性及构效关系奠定一定基础。     

High performance wood composites based on benzoxazine-epoxy alloys

Wood-substituted composites from matrices based on ternary mixtures of benzoxazine, epoxy, and phenolic novolac resins (BEP resins) using woodflour (Hevea brasiliensis) as filler are developed. The results reveal that the addition of epoxy resin into benzoxazine resin can lower the liquefying temperature of the ternary systems whereas rheological characterization of the gel points indicates an evident delay of the vitrification time as epoxy content increased. The gelation of the ternary mixtures shows an Arrhenius-typed behavior and the gel time can be well predicted by an Arrhenius equation with activation energy of 35-40kJ/mol. For wood-substituted composites from highly filled BEP alloys i.e. at 70% by weight of woodflour, the reinforcing effect of the woodflour shows a substantial enhancement in the composite stiffness i.e. 8.3GPa of the filled BEP811 vs 5.9GPa of the unfilled BEP811. The relatively high flexural strength of the BEP wood composites up to 70MPa can also be obtained. The outstanding compatibility between the woodflour and the ternary matrices attributed to the modulus and thermal stability enhancement of the wood composites particularly with an increase of the polybenzoxazine fraction in the BEP alloys.     

Polarographic studies of ion binding in solutions of pepsin. II. Binding of thallous ions

The results of the application of a modified polarographic method to the study of binding of thallous ions in solutions of pepsin are reported. Isoionic solutions of pepsin were converted by using a cation exchange resin to solutions of thallous pepsin. The extent of ion binding was obtained as in the case of cadmium pepsin by assuming that only free, i.e., unbound, ions contribute to the diffusion and migration currents, respectively. However, the relations used previously for computing the degree of ion binding have been refined on the basis of experience acquired in a parallel study of solutions of thallous acrylate and polyacrylate, respectively.     

接枝共聚法合成多彩水晶花泥

采用水溶性引发剂,以N'N'-亚甲基双丙烯基酰胺为交联剂,表面活性剂为助剂进行丙烯酸和彩色聚丙烯酸脂接枝共聚,合成多彩水晶花泥。制得的共聚物可吸水100倍以上,形成水凝胶呈水晶多棱结构,色彩艳丽且色泽牢固、不溶于水、无毒、无污染,可用于家庭花卉无土培养、室内插花装饰等。本文讨论引发剂、交联剂、助剂等合成条件对共聚物性能的影响。     

Enzymatic synthesis of oleic acid-based epoxy monomer for the production of value added polymers

An oleic acid-based epoxy monomer was synthesized by reacting 2-hydroxyethyl acrylate with epoxy stearic acid and an immobilized lipase. NMR, electrospray ionization mass spectrometry and gel permeation chromatography were used to characterize the intermediates and products. 2-(Acryloyloxy) ethyl epoxy stearate was synthesized with a yield of 87 % w/w. After free radical polymerization, epoxy stearic acid-grafted epoxy polymer with molecular weight of 15,150 g/mol was obtained; the final yield was 81 % w/w.     

Biodegradation and sorption properties of polydisperse acrylate polymers

Polyacrylate (PA), which is widely used in disposable diapers, is synthesized by polymerization and cross-linking of acrylate. During the synthesis, 3–6% of the polyacrylate polymers is not incorporated into the absorbent material, but remains soluble. If the soluble PA is mobilized from a landfill, it could enter the groundwater. Therefore, the biodegradation and adsorption properties of soluble polymers contained in PA are determined in this study. The soluble PA is highly polydisperse, and the fraction tested has a weight-average molecular-weight of 16,700 and a range extending from 10³ to 10⁵. Sand-column tracer tests show that about 1% of the polyacrylate is unadsorbed, but the remainder has a retardation factor that averages at least 58. Biodegradation kinetics are determined in completely mixed biofilm reactors having a methanogenic consortium grown on glucose. The polyacrylate fraction, as well as glucose and acrylate, are removed and mineralized to CO₂. The Monod parameters for the polyacrylate are: maximum specific rate of substrate utilization = 0.0016 gC/g biomass-day, and half-maximum-rate concentration = 0.79 gC/m³. Although these kinetics are much slower than for glucose and acrylate, significant degradation and mineralization are observed.     

兼性厌氧纤维素菌的分离与系统发育分析

从四川卧龙中国保护大熊猫研究中心提供的野外放归大熊猫“祥祥”的粪样中,分离到一株产纤维素酶的兼性厌氧菌株。该菌株经初步生理生化鉴定为肠杆菌科沙雷氏菌（Serratia）,命名为Serratia JF-1116。用PCR技术扩增了该菌的16S rDNA全序列,并对其进行了克隆和测序,对该序列在GenBank中的BLAST结果表明,所有与该序列高度同源的序列均为肠杆菌科的16SrDNA基因序列,选取同源性高的菌株的16SrDNA基因序列进行系统发育分析,菌株与3株Serratia聚类在一起。     

Lipase-catalyzed acyiation of sugars solubilized in hydrophobic solvents by complexation

By complexing glucose and other mono- and disaccharides with phenylboronic acid, they were solubilized in many organic solvents. Pseudomonas sp. lipoprotein lipase readily acylated such solubilized sugars in these solvents (no reaction was observed without phenylboronic acid, i.e., when sugars are insoluble in the reaction medium). Solubilized D-glucose was enzymatically acylated with vinyl acrylate on a preparative scale, and the resultant 6-O-acryloylglucose was chemically polymerized to yield a sugar-based polyacrylate with a molecular weight of 14,000 Da. (c) 1993 John Wiley & Sons, Inc.     

Attenuating the size and molecular carrier capabilities of polyacrylate nanoparticles by a hydrophobic fluorine effect

This study investigates the effect of introducing alkyl chain fluorination on the properties of polyacrylate nanoparticles prepared in aqueous solution by emulsion polymerization. For this, 2,2,3,3,4,4,4-heptafluorobutyl acrylate (1) and methyl trifluoroacrylate (2) were tested as monomers as a means to prepare fluorinated polyacrylate nanoparticles to evaluate how side chain fluorination may affect nanoparticle size and drug carrier properties. Our results show that as fluorine content within the polyacrylate matrix increases, the size of the nanoparticle systematically diminishes, from 45nm (for nanoparticles containing no fluoroacrylate) to ～7nm (for nanoparticles constructed solely of fluoroacrylate). We also observe that as fluoroacrylate content and hydrophobicity increases, the nanoparticles decrease their ability to incorporate lipophilic molecules during the process of emulsification. These findings have meaningful implications in the implementation of fluorinated nanoparticles in molecular delivery.     

Citromicrobium bathyomarinum, a novel aerobic bacterium isolated from deep-sea hydrothermal vent plume waters that contains photosynthetic pigment-protein complexes.

We have taxonomically and phylogenetically characterized a new aerobic bacterial strain (JF-1) that contains photosynthetic pigment-protein complexes and which was recently isolated from black smoker plume waters of the Juan de Fuca Ridge. Strain JF-1 is a gram-negative, yellow-pigmented, motile bacterium that is salt-, pH-, and thermotolerant. These properties are consistent with an oligotrophic adaptation to varied environmental conditions thought to exist around deep-sea hydrothermal vents. The analysis of 16S rDNA sequences revealed that strain JF-1 forms a separate phylogenetic branch between the genus Erythromonas and the Erythromicrobium-Porphyrobacter-Erythrobacter cluster within the alpha subclass of the Proteobacteria. The taxonomic name Citromicrobium bathyomarinum (gen. nov., sp. nov.) is proposed for strain JF-1.     

Structural-based mutational analysis of D-aminoacylase from Alcaligenes faecalis DA1

D-Aminoacylase is an attractive candidate for commercial production of D-amino acids through its catalysis in the zinc-assistant hydrolysis of N-acyl-D-amino acids. We report here the cloning, expression, and structural-based mutation of the D-aminoacylase from Alcaligenes faecalis DA1. A 1,007-bp PCR product amplified with degenerate primers, was used to isolate a 4-kb genomic fragment, encoding a 484-residue D-aminoacylase. The enzyme amino-terminal segment shared significant homology within a variety of enzymes including urease. The structural fold was predicted by 3D-PSSM to be similar to urease and dihydroorotase, which have grouped into a novel alpha/beta-barrel amidohydrolase superfamily with a virtually indistinguishable binuclear metal centers containing six ligands, four histidines, one aspartate, and one carboxylated lysine. Three histidines, His-67, His-69, and His-250, putative metal ligands in D-aminoacylase, have been mutated previously, the remaining histidine (His-220) and aspartate (Asp-366) Asp-65, and four cysteines were then characterized. Substitution of Asp-65, Cys-96, His-220, and Asp-366 with alanine abolished the enzyme activity. The H220A mutant bound approximately half the normal complement of zinc ion as did H250N. However, the C96A mutant showed little zinc-binding ability, revealing that Cys-96 may replace the carboxylated lysine to serve as a bridging ligand. According to the urease structure, the conserved amino-terminal segment including Asp-65 may be responsible for structural stabilization.