以改性Al2O3为载体固定化葡萄糖氧化酶的研究

本文采用吸附和交联、生物和非生物催化剂结合的方法,制得活性高、稳定性好并以Al_2O_3.为载体的固定化葡萄糖氧化酶,其性能优于文献报导的结果.     

IMMOBILIZATION OF Saccharomyces Cerevisiae USING POLY(ACRYLAMIDE)GEL FOR ASYMMETRIC SYNTHESIS OF R(-)-MANDELIC ACID

1. INTRODUCTIONPoly(acrylamide) hydrogel (PAAm gel), which is able to swell, but cannot be dissolved in the aqueous environment, is a three-dimension network with repeating hydrophilic units -CONH2. Since PAAm gel has a good biocompatibility as well as a high mechanical strength, and can be easily separated from reaction medium, PAAm gel has often been employed to immobilize enzymes and cells so as to catalyze various of chemical and biochemical reactions [1,2]. So far, biosynthesis …     

Electrochemical Parameters of Phenoxazine Derivatives in Solution and at Monolayer‐Modified Gold Electrodes

Electrochemical properties of β‐(10‐phenoxazinyl) propylamine (APPX) and β‐(10‐phenoxazinyl) propionic acid (PPX) have been studied in solution, and in immobilized state on gold electrodes modified with monolayers of cystamine and mercaptoundecanoic acid. A reversible diffusion‐controlled process of APPX and PPX was observed at a bare gold electrode. The electrochemical conversion of both compounds at modified gold electrodes was a quasi‐reversible diffusion‐controlled process. The redox potential of immobilized APPX (443 mV) was similar to the potential in solution, while the value of the immobilized PPX was 131 mV higher than in solution. The immobilized mediators were electrocatalytically active in the fungal peroxidase‐catalyzed hydrogen peroxide reduction.     

The preparation of immobilized stationary phase fused silica capillary columns with OV-1701-vinyl deactivation

A new simplified method was developed for the preparation of immobilized stationary phase fused silica capillary columns coated with OV-1-vinyl, SE-54, and OV-1701-vinyl. This methodology includes the application of the moderately polar stationary phase OV-1701-vinyl as a surface deactivation agent that may also participate in the dicumyl peroxide initiated free radical immobilization process. Practical details of the procedure are presented and applications of the laboratory-produced columns are illustrated with capillary gas chromatographic separations of standard mixtures. Possible contributions of the OV-1701-vinyl deactivation layer to both crosslinking and surface bonding in the immobilization process are discussed.     

Functionalization of cellulose dialysis membranes for chiral separation using beta-cyclodextrin immobilization

A membrane-based chiral separation system for the separation of racemic tryptophan solutions is developed by the covalently binding beta-cyclodextrin onto the surface of commercial cellulose membranes. The immobilization process is monitored by XPS. AFM demonstrates the evolutionary transition of membrane surface morphology before and after the CD immobilization. Due to their different complexation with immobilized CD, dialysis transport experiments show d-tryptophan preferential permeability through the immobilized CD membranes, and the enantioselectivity is 1.10. A model based on the existence of a thin chiral solution layer of amino acid at the interface between the feed solution and the membrane has been proposed. This chiral separation model has been verified using the chiral separation results of racemic amino acids and binding constants of amino acids with CD. The effect of membrane's pore size on enantioselectivity has also been investigated. The immobilized CD membrane, having MWCO 1000, exhibits the highest enantioselectivity to the racemic tryptophan solution.     

Regio- and stereoselective hydrosilylation of immobilized terminal alkynes

Regio- and stereoselective hydrosilylation of terminal alkynes on solid support using diisopropyl hydrosilanes yielding β-(E)-vinyl silanes with excellent selectivity is reported. The hydrosilylation is catalyzed by Pt(DVDS)/P(ⁱBuNCH₂CH₂)₃N (DVDS = 1,3-divinyl-1,1,3,3-tetramethyl-disiloxane), in which the bulky proazaphosphatrane ligand plays a key role for the selectivity. The immobilized products are characterized with gel phase¹³C NMR and ¹H high resolution magic angle spinning NMR.     

水分荧光光纤化学传感器

将具有溶致变色特性的４‘－Ｎ,Ｎ－二甲氨基黄酮基团与聚丙烯酰胺膜基体一起共价固定化在石英玻片上,制成了测定水的光导纤维化学传感器。传感是基于水对膜的荧光有强的猝灭作用。文中提出了猝灭方程。传感器具有好的可逆性和稳定性,重复测定含水４．００％和１６．０％的乙醇样品的相对标准偏差分别为０．３３％和０．６０％,这说明传感器还具有好的重现性。传感器用于９５％乙醇中水分的含量测定,结果与气相色谱法一致。     

DNA修饰电极的研究(Ⅸ)--DNA探针在金基底上的固定、表征及其表面分子杂交

采用疏基化合的自组装／共价键合反应的逐层固定方法将双链DNA固定到金表面得到DNA修饰电极,并对该电极表面进行了电化学和X射线光电子能谱表征。研究了电极表面固定化DNA的表面分子杂交。对开发电化学基因诊断芯片和基因传感器具有一定意义。     

聚苯胺用作乙醇脱氢反应中的电子传递介质

脱氢酶（ADH）在电化学氧化还原反应中是很重要的一种酶,但它在催化有机分子脱氢反应时需烟酰胺腺嘌呤二核苷酸（NAD＋）参与,后者从底物接收电子生成还原形NADH.脱氢酶电极是根据NADH的电化学氧化产生的阳极电流构成的[1－3].然而NADH与裸体炭电极和铂金电极之间的直接电子传递是非常困难的,往往需一个相当高的过电位[4].另一个问题是生成物易将电极玷污[5,6].克服这些问题的方法是使用均相电子传递介质,例如在底物溶液中加入Meldola蓝、Nile蓝A和NMP＋甲替硫酸盐等[7－9],及复相电子传递介质,例如将镍六氰基高铁酸盐固…