Determination of sulfur dioxide in vitriol plant wastewater by using a polyNiMe4TAA electrochemically modified Pt microelectrode

A Pt microelectrode modified with nickel(II) polytetramethyldibenzo[b,i]tetraaza[14]annulene was prepared by electropolymerization of nickel(II) tetramethyldibenzo[b,i]tetraaza[14]annulene monomers and applied to determine sulfur dioxide in vitriol plant wastewater. For determination of SO2 with this electrochemically modified Pt microelectrode, the linear range was from 9.6 x 10(-6) to 2.4 x 10(-4) mol L-1, the sensitivity was 1.8 x 10(-4) A L mol-1, the detection limit was calculated to be 4.8 x 10(-6) mol L-1 (S/N = 3), the response time was less than 20 s and the relative standard deviation was found to be 2.1% on analyzing 4.8 x 10(-5) mol L-1 SO2 solution repeatedly (n = 7). These results demonstrated good accuracy compared with those obtained by the conventional iodimetric method.     

红四氮唑作为电化学嵌合剂的核酸杂交生物传感器

提出了一种以红四氮唑 (TTC)作为嵌合剂 ,采用石墨修饰电极监测核酸杂交过程和测定特定 DNA片段的灵敏的电化学方法 . TTC具有背景电流低 ,电活性强和对双链 DNA(ds DNA)选择性好等一系列优点 ,可在石墨电极表面形成 ds DNA-TTC层 .在电化学测定中 ,TTC的还原电流与靶 DNA浓度具有良好的线性关系 ,对 DNA的检测限可低达 6× 1 0 - 1 1 mol/L .     

Zn-Fe-SiO2复合镀层的制备工艺及其耐蚀性研究

在酸性硫酸盐体系中电沉积制备了Zn-Fe-SiO2复合镀层,并研究了工艺因素对镀层SiO2含量的影响.随着电流密度由4.8A/dm2增加到6A/dm2时,镀层中SiO2的含量由0.21%上升到0.47%,但是当电流密度继续增加到7.2A/dm2时,SiO2含量反而下降到了0.18%.当镀液中SiO2浓度由20g/L增加到60g/L时,镀层中SiO2含量由0.40%上升到0.51%.当镀液pH值由2增加到4时,镀层中SiO2含量由0.22%上升到1.17%.采用5%NaCl溶液浸泡试验考察了Zn镀层、Zn-Fe合金镀层与Zn-Fe-SiO2复合镀层的耐蚀性,并研究了镀层中SiO2含量对镀层耐蚀性的影响.结果表明,Zn-Fe-SiO2复合镀层无需钝化处理,其耐蚀性优于Zn镀层及Zn-Fe合金镀层,并且镀层的耐蚀性随着镀层中SiO2含量增大而提高.     

Preorganization and reorganization as related factors in enzyme catalysis: the chorismate mutase case

In this paper a deeper insight into the chorismate-to prephenate-rearrangement, catalyzed by Bacillus subtilis chorismate mutase, is provided by means of a combination of statistical quantum mechanics/molecular mechanics simulation methods and hybrid potential energy surface exploration techniques. The main aim of this work is to present an estimation of the preorganization and reorganization terms of the enzyme catalytic rate enhancement. To analyze the first of these, we have studied different conformational equilibria of chorismate in aqueous solution and in the enzyme active site. Our conclusion is that chorismate mutase preferentially binds the reactive conformer of the substrate--that presenting a structure similar to the transition state of the reaction to be catalyzed--with shorter distances between the carbon atoms to be bonded and more diaxial character. With respect to the reorganization effect, an energy decomposition analysis of the potential energies of the reactive reactant and of the reaction transition state in aqueous solution and in the enzyme shows that the enzyme structure is better adapted to the transition structure. This means not only a more negative electrostatic interaction energy with the transition state but also a low enzyme deformation contribution to the energy barrier. Our calculations reveal that the structure of the enzyme is responsible for stabilizing the transition state structure of the reaction, with concomitant selection of the reactive form of the reactants. This is, the same enzymatic pattern that stabilizes the transition structure also promotes those reactant structures closer to the transition structure (i.e., the reactive reactants). In fact, both reorganization and preorganization effects have to be considered as the two faces of the same coin, having a common origin in the effect of the enzyme structure on the energy surface of the substrate.     

PREPARATION AND STUDY ON SILICONE ACRYLATE MICRO-EMULSION OF MULTIPOLYMER

A silicone acr3,1ate micro-emulsion of multipolymer was prepared by seed emulsion polymeri.Tation. The effects of polymerization process, emulsifier rate and amount, initiator rate and amounl, polymerization temperalure, functional monomers, titration time on performances of emulsion have been discussed in detail.     

芯片毛细管电泳程控电源的研制

设计并制作了一种小型的、可与PC机相联的程序控制电源，其中有两路输出电压，用于芯片毛细管电泳的分离和进样；而且，可程序控制输出电压和运行时间，并在PC机上以图形方式显示是泳电流。该电源适用于芯片毛细管电泳的过程监控。     

A novel diacetylenic bilirubin

An etiobilirubin‐IIβ analog with the central C(10) CH₂ group replaced by a diacetylene unit ( 1 ) was synthesized by base‐catalyzed condensation of bis‐[3‐methyl‐4‐ethyl‐5‐formylpyrrol‐2‐yl]‐diacetylene ( 3 ) with 3‐methyl‐4‐ethyl‐5‐p‐toluenesulfonyl‐2‐pyrrolinone ( 10 ). Diacetylenic rubin 1 is a dark red solid, giving orange solutions with uv‐visible absorption maxima near 460 nm.     

Quinine/selectfluor combination induced asymmetric semipinacol rearrangement of allylic alcohols: an effective and enantioselective approach to alpha-quaternary beta-fluoro aldehydes

A quinine/Selectfluor combination inducing rearrangement reaction of allylic alcohols was discovered, which involved a moderate yield with good enantioselective construction of alpha-quaternary carbon center and beta-fluoro aldehyde under base condition.     

Microwave-assisted solvent-free synthesis of substituted 2-quinolones

A rapid and efficient method for the preparation of a variety of substituted 2-quinolones has been developed through the reactions of o-aminoarylketones with ester compounds containing a reactive α-methylene moiety in the presence of a catalytic amount of cerium chloride heptahydrate under solvent-free conditions in high yields. The rate and yield of the reaction are considerably improved by employing microwave irradiation.     

Michael-Addition Reaction of Malononitrile with α,β-Unsaturated Cycloketones Catalyzed by KF／Al2O3

A series of KF/Al2O3 catalyzed Michael-addition reactions between malononitrile and α,β-unsaturated cycloketones in DMF solution were studied. At room temperature, 2-cyano-3-aryl-3-(1,2,3,4-tetrahydronaphthalen-1-one-2-yl) propionitrile derivatives were synthesized by the reaction between 2-arylmethylidene-1,2,3,4-tetra-hydronaphthalen-1-one and malononitrile. However, if the temperature was increased to 80℃, 2-amino-3-cyano-4-aryl-4H-benzo[h]chromene derivatives were obtained in high yields. When the α,β-unsaturated ketones were replaced by 2,6-biarylmethylidenecyclohexanone or 2,5-biarylmethylidenecyclopentanone, another series of 2-amino-3-cyano-4H-pyran derivatives was isolated successfully. The structures of the products were confirmed by X-ray diffraction analysis.