Reductive alkylation of lipase

Candida rugosa lipase was modified via reductive alkylation to increase its hydrophobicity to work better in organic solvents. The free amino group of lysines was alkylated using propionaldehyde with different degrees of modification obtained (49 and 86%). Far-ultraviolet circular dichroism (CD) spectroscopy of the lipase in aqueous solvent showed that such chemical modifications at the enzyme surface caused a loss in secondary and tertiary structure that is attributed to the enzyme unfolding. Using molecular modeling, we propose that in an aqueous environment the loss in protein structure of the modified lipase is owing to disruption of stabilizing salt bridges, particularly of surface lysines. Indeed, molecular modeling and simulation of a salt bridge formed by Lys-75 to Asp-79, in a nonpolar environment, suggests the adoption of a more flexible alkylated lysine that may explain higher lipase activity in organic solvents on alkylation.     

Nanopore and nanoparticle catalysts

The design, atomic characterization, performance, and relevance to clean technology of two distinct categories of new nanocatalysts are described and interpreted. Exceptional molecular selectivity and high activity are exhibited by these catalysts. The first category consists of extended, crystallographically ordered inorganic solids possessing nanopores (apertures, cages, and channels), the diameters of which fall in the range of about 0.4 to about 1.5 nm, and the second of discrete bimetallic nanoparticles of diameter 1 to 2 nm, distributed more or less uniformly along the inner walls of mesoporous (ca. 3 to 10 nm diameter) silica supports. Using the principles and practices of solid-state and organometallic chemistry and advanced physico-chemical techniques for in situ and ex situ characterization, a variety of powerful new catalysts has been evolved. Apart from those that, inter alia, simulate the behavior of enzymes in their specificity, shape selectivity, regio-selectivity, and ability to function under ambient conditions, many of these new nanocatalysts are also viable as agents for effecting commercially significant processes in a clean, benign, solvent-free, single-step fashion. In particular, a bifunctional, molecular sieve nanopore catalyst is described that converts cyclohexanone in air and ammonia to its oxime and caprolactam, and a bimetallic nanoparticle catalyst that selectively converts cyclic polyenes into desirable intermediates. Nanocatalysts in the first category are especially effective in facilitating highly selective oxidations in air, and those in the second are well suited to effecting rapid and selective hydrogenations of a range of organic compounds.     

Biomimetic selectivity

Synthetic organic chemistry normally achieves selectivity by manipulation of the intrinsic reactivity of the substrate, but enzyme use is quite a different principle. The geometry of the enzyme-substrate complex determines enzymatic selectivity, completely overwhelming any normal selective reactivities. Biomimetic chemistry aims to imitate the enzymatic style. Some early approaches used attached reagents or templates to direct photochemical and free radical processes, with a combination of geometric and reactivity control. Recent work uses a mimic of the enzyme class cytochrome P-450 to achieve the selective hydroxylations of steroids with complete domination by the geometry of the catalyst-substrate complex.     

菲咯啉铜配合物模拟过氧化物酶检测过氧化氢

以菲咯啉铜[Cu(OP)2]配合物模拟辣根过氧化物酶催化过氧化氢与邻苯二胺反应,研究了不同反应条件对催化活性的影响.据此,建立了以菲咯啉铜模拟酶体系检测过氧化氢的灵敏方法.测定所用的试剂不含辣根过氧化物酶,从而避免了生物酶在使用过程中因可能的失活给分析工作带来的困难.在最佳条件下,过氧化氢浓度在9.5×10-8~1.67×10-6mol/L的范围内与体系吸光度成良好的线性关系.检测极限为8.0×10-8mol/L.     

Amperometric lactate biosensors and their application in (sports) medicine, for life quality and wellbeing

The article reviews the use of electrochemical biosensors for detecting lactate, a key metabolite of the anaerobic glycolytic pathway. This compound plays an important role in (sports) medicine, in the nutritional sector, in food quality control and touches environmental concerns. Amperometric biosensors offer a sensitive and selective means to monitor organic analytes like lactate. A detailed study on different aspects of amperometric lactate biosensor preparation is described: the main configuration aspects are compiled regarding electrode materials, biorecognition elements, immobilization methods, mediators and cofactors as well as fields of application. Comparative studies are conducted correlating different configuration aspects and performance of the resulting biosensors. This review contains 214 references from the years 1974 to 2007. Correspondence: Beate Strehlitz, UFZ, Helmholtz Centre for Environmental Research – UFZ, Environmental and Biotechnology Centre (UBZ), Permoserstrasse 15, D-04318 Leipzig, Germany     

红外光谱分析木质素在漆酶酶法改性中的反应性

随着非水酶学的发展,木质素的酶法催化改性得到日益广泛的运用。文章主要考察了漆酶酶法改性反相微乳液体系中云杉碱木质素、乙醇水溶液中乙醇木质素、缓冲液体系中木质素磺酸盐、以及碱溶液中汽爆麦草碱木质素的反应。通过红外光谱对各反应体系中,漆酶催化改性后的木质素结构特点进行分析,结合凝胶色谱法考察木质素的分子量及其分布,结果表明经过YY-5漆酶处理后各种木质素的分子量分布均趋向于高分子区域,且分子量分散性降低,各种木质素的红外光谱结构也发生了明显的变化。初步确定了木质素在漆酶催化改性中存在的反应位点,主要是酚羟基、苯环侧链取代基、羰基等。在四种木质素中,漆酶对碱木质素的改性反应性要高于其他类型的木质素,这可能与碱性溶液体系中漆酶的活性较高有关。     

银鲳不同消化器官中消化酶活性的分布及其比较

为了解野生与养殖条件下银鲳不同消化器官中消化酶活性的分布,比较研究了野生银鲳成鱼和养殖银鲳幼鱼的消化酶(蛋白酶、淀粉酶、脂肪酶)活性.结果表明:(1)成鱼胃中蛋白酶活性最大,为0.47U·mg-1,侧囊中蛋白酶活性最小,仅有0.05 U·mg-1;成鱼肝中淀粉酶活性最大,为0.08U·mg-1,直肠最小,为0.01 U·mg-1;肝的脂肪酶活性最大,为10.63 U·mg-1,中肠最小,肝脂肪酶活性约为中肠的9倍.(2)幼鱼三种消化酶活性均为:胃肝侧囊,且银鲳幼鱼各消化酶活性总体上高于成鱼,幼鱼胃中蛋白酶活性、淀粉酶活性、脂肪酶活性分别约为成鱼胃的3倍、12倍和1.5倍.(3)银鲳成鱼和幼鱼的A/P值都小于1,且幼鱼各消化器官的A/P值都大于成鱼,A/P值结果表明银鲳为偏肉食性鱼类,野生的成鱼比养殖的幼鱼更适应肉食性.此外,研究还发现银鲳的脂肪酶活性明显高于许多常见海水性鱼类,推断其对脂肪的利用效率较高,可以考虑在银鲳饲料的配制时适当提高饲料中脂肪的比例.     

硼上去烃化反应中的共生效应

考察三（２－苯并呋喃基）硼烷、三（２－呋喃基）硼烷及三（２－噻吩基）硼烷被某些β－二酮（乙酰丙酮、二苯甲酰基甲烷、二茂铁基甲酰丙酮）去烃化的能力，及其产物β－二酮螯合物在电子电离质谱反应中的再去烃化差异．结果证实，受共生效应支配，共生性配体２－苯并呋喃核及２－呋喃核比非共生性配体２－噻吩核均较难从硼原子上裂去．     

2-酮戊二酸对水稻根部碳-氮代谢重要酶的活性影响

2-酮戊二酸是碳-氮代谢的重要调控因子，在培养液中添加2-酮戊二酸可以促进水稻幼苗根部碳-氮代谢酶的活性．为了确定2-酮戊二酸是否与这些酶之间存在直接作用（体内实验），取正常培养的水稻幼苗材料，在上述酶的测活体系中分别添加2-酮戊二酸，并进行酶活性测定（体外实验）．实验结果表明：2-酮戊二酸可以促进水稻幼苗根组织提取液中GS，HXK的活性，而对GOGAT，ICDH没有明显的影响．上述结果说明2-酮戊二酸作为一种效应物可能与GS、HXK结合，从而在体内、体外都促进了它们的活性．