Studies on the Catalytic Promiscuity of Limonene Epoxide Hydrolases in the Non-hydrolytic Ring Opening of 1,2-Epoxides

The non-hydrolytic ring opening of 1,2-epoxides in the presence of limonene epoxide hydrolases (LEHs) and different nucleophiles has been investigated. Lyophilized, wild-type LEHs were tested in selected water-saturated organic solvents in the presence of cyclohexene oxide as substrate and different alcohols, thiols and primary amines as nucleophiles. Although the LEHs retained an appreciable catalytic activity under different reaction conditions, formation of the desired 1,2-substituted cyclohexanols was not observed. Alternatively, LEH variants incapable of performing the hydrolytic reaction were generated by site-directed mutagenesis and tested in aqueous media in the presence of different water-soluble nucleophiles and cyclohexene oxide. Under defined reaction conditions, an acceleration of up to about threefold of the spontaneous reaction rate was observed in the presence of sodium azide and potassium thiocyanate as nucleophiles.     

有机溶剂中酶多功能性催化有机合成反应

近年来,酶的多功能性广泛应用于有机合成反应.本文综述了有机溶剂中水解酶、氧化还原酶、转移酶和裂解酶催化有机合成反应.     

漆酶的结构与催化反应机理

漆酶是一种广泛分布的多酚氧化酶,主要由单一多肽、铜离子活性中心、糖配基组成。多肽链一般含有18种氨基酸,构成漆酶的结构主体;糖配基因漆酶的来源不同而异,是漆酶多样性的标志之一。漆酶活性中心的铜离子依据光学和磁学特性被分为3种类型:Ⅰ型或蓝型铜,Ⅱ型或通常型铜,Ⅲ型或偶联的双核型铜。漆酶的催化反应机理主要包括酶对底物的电子提取、电子的传递和氧分子对酶的还原三步,是一个通过电子转移发生氧化还原反应的过程。     

Extended Catalytic Scope of a Well‐Known Enzyme: Asymmetric Reduction of Iminium Substrates by Glucose Dehydrogenase

NADP(H)‐dependent imine reductases (IREDs) are of interest in biocatalytic research due to their ability to generate chiral amines from imine/iminium substrates. In reaction protocols involving IREDs, glucose dehydrogenase (GDH) is generally used to regenerate the expensive cofactor NADPH by oxidation of d ‐glucose to gluconolactone. We have characterized different IREDs with regard to reduction of a set of bicyclic iminium compounds and have utilized ¹H NMR and GC analyses to determine degree of substrate conversion and product enantiomeric excess (ee). All IREDs reduced the tested iminium compounds to the corresponding chiral amines. Blank experiments without IREDs also showed substrate conversion, however, thus suggesting an iminium reductase activity of GDH. This unexpected observation was confirmed by additional experiments with GDHs of different origin. The reduction of C=N bonds with good levels of conversion (>50 %) and excellent enantioselectivity (up to >99 % ee) by GDH represents a promiscuous catalytic activity of this enzyme.     

轻质烷烃异构化催化剂及机理研究进展

简介了近年来国内外轻质烷烃异构化新工艺和新催化剂,综述了近年来的经典及新提出的异构化反应机理。根据反应机理针对不同催化剂体系总结了提高异构催化剂反应活性和选择性的途径,并展望了反应机理在制备新型催化剂领域以及提高催化剂的活性和选择性方面的重要指导意义。     

Pharmacological Promiscuity: Dependence on Compound Properties and Target Specificity in a Set of Recent Roche Compounds

What parameters determine promiscuity? A compound's potential for promiscuity (pharmacological activity at multiple targets) may be influenced by molecular parameters such as ionization state, lipophilicity, and molecular weight. In an analysis of recent Roche compounds we found that a positive charge is an important determinant for potential promiscuity; aminergic activity was found to be the main reason for overt promiscuity.

     

甲醇合成铜基催化剂催化活性及失活研究

主要介绍了甲醇合成铜基催化剂及其催化机理,并从制备条件和反应条件等方面对催化剂活性的影响因素进行了探讨,最后对造成催化剂失活的因素进行了具体研究。     

Forty Years of Designing Catalytic and Adsorptive Sites in FAU Type Zeolites at K.U. Leuven

An overview of scientific achievements at K.U. Leuven on the design and characterization of active sites in X and Y zeolites and on the development of adsorptive and catalytic processes in which these active sites are operated is provided. The historical development of this research area and the scientific progress are presented. Zeolite Y and ultrastabilized specimen present Brønsted and Lewis sites that can be operated in vapor and liquid phase hydrocarbon conversion processes, bifunctional catalysis, epoxidation and ring opening of epoxides. Examples of molecular shape selective catalysis with Y zeolites are presented. The redox chemistry of transition metal exchanged faujasites is understood in great detail and has been exploited in Wacker chemistry and water splitting in a photochemical-thermal cycle. Selective adsorbents were designed based on knowledge of cation siting in X and Y zeolites. The occlusion of coordination compounds in the faujasite supercages is a means of creating unique active sites. Catalytic oxidative properties of the enzymes can be mimicked by embedding zeozyme in a hydrophobic membrane.