Novel aspects of glypican glycobiology

Mutations in glypican genes cause dysmorphic and overgrowth syndromes in men and mice, abnormal development in flies and worms, and defective gastrulation in zebrafish and ascidians. All glypican core proteins share a characteristic pattern of 14 conserved cysteine residues. Upstream from the C-terminal membrane anchorage are 3–4 heparan sulfate attachment sites. Cysteines in glypican-1 can become nitrosylated by nitric oxide in a copper-dependent reaction. When glypican-1 is exposed to ascorbate, nitric oxide is released and participates in deaminative cleavage of heparan sulfate at sites where the glucosamines have a free amino group. This process takes place while glypican-1 recycles via a nonclassical, caveolin-1-associated route. Glypicans are involved in growth factor signalling and transport, e.g. of polyamines. Cargo can be unloaded from heparan sulfate by nitric oxide-dependent degradation. How glypican and its degradation products and the cargo exit from the recycling route is an enigma.Received 27 November 2003; received after revision 8 January 2004; accepted 13 January 2004     

明胶-十二烷基硫酸钠复配体系表面活性的研究

对明胶－十二烷基硫酸钠(SDS)复配体系,研究了SDS浓度、明胶浓度、明胶种类及分子量对其表面活性的影响。实验结果表明,随着SDS浓度的增加,体系的表面张力降低,并在其变化曲线中有一“平台”区域,同时体系的乳化力增大,其乳化力顺序为纯SDS溶液>水解皮明胶－SDS>水解骨明胶－SDS>骨明胶－SDS>皮明胶－SDS体系;各体系的起泡力及其稳定性亦随之增大。而明胶浓度的增加导致了各明胶－SDS体系表面张力的增大,且明胶浓度对大分子明胶体系的影响较之小分子明胶体系要大;明胶浓度的增加降低了体系的泡沫稳定性;但明胶浓度及其种类、分子量对体系的乳化力影响不大。     

<Emphasis Type="Italic">In situ</Emphasis> generation and detection of methyl radical by voltammetry

The chemistry of free radicals is one of the advanced subjects of fundamental sciences such as biomedicine, environment protection, new energy sources and new material. The detection technique of free radicals is an essential tool for studying free radicals. Methyl radical is one of the representatives of alkyl radicals and the studies on it attract more attention. The current approaches to obtaining methyl radical are based on pulse radiolysis of organic substances that contain the methyl gro…     

硫酸氢钠催化合成苹果酯-B

探讨了硫酸氢钠对苹果酯-B合成反应的催化活性,研究了催化剂用量、乙酰乙酸乙酯与1,2-丙二醇反应的最佳物质的量之比以及反应时间等因素对产品收率的影响.实验表明,硫酸氢钠是合成苹果酯-B的优良催化剂,在n(乙酰乙酸乙酯)∶n(1,2-丙二醇)=1.0∶1.7,催化剂用量为反应物总摩尔分数的0.67%时,环己烷作带水剂,反应时间为1.0h的优化条件下,苹果酯-B的收率可达到90.2%.     

Heterogeneous oxidation of carbonyl sulfide on mineral oxides

Heterogeneous oxidation of carbonyl sulfide (OCS) on mineral oxides including SiO2,Fe2O3,CaO,MgO,ZnO and TiO2,which are the main components of atmospheric particles,were investigated using in situ diffuse reflectance infrared Fourier transform spectroscopy (in situ DRIFTS),ion chromatography (IC),temperature-programmed desorption (TPD),X-ray diffraction (XRD) and Brunauer-Emmett-Teller (BET) methods. The main products and intermediates of the heterogeneous oxidation of OCS on these oxides were identified with in situ DRIFTS and IC. The reaction mechanism and kinetics were also discussed. It is found that the reaction mechanism on these mineral oxides is the same as that on Al2O3 for the same final products and the intermediates at room temperature. Namely,OCS can be catalytically oxidized to produce surface SO42- species and gaseous CO2 through the surface hydrogen thiocarbonate (HSCO2-) and HSO3- species. The activity series for heterogeneous oxidation of OCS follows: Al2O3 ≈ CaO > MgO > TiO2 ≈ ZnO > Fe2O3 > SiO2. The specific area,basic hydroxyl and surface basicity of these oxides have effect on the reactivity. This study suggests that heterogeneous reactions of OCS on mineral dust may be an unneglectable sink of OCS.     

PDMDAAC-PFS复合絮凝剂处理硅藻土悬浊液的絮体分形特征

采用扫描电镜考察了聚二甲基二烯丙基氯化铵-聚合硫酸铁复合絮凝剂(PDMDAAC-PFS)处理硅藻土悬浊液的絮体形貌,并与单独使用PDMDAAC和PFS产生的絮体进行比较.运用密度-密度相关函数计算了絮体的分维,探讨了絮体的结构、分维与沉降速度的关系.结果表明,使用PDMDAAC-PFS产生的硅藻土絮体分维为1.89,比单独使用PFS和PDMDAAC产生的絮体分维大(分维分别为1.67和1.55),其沉降速度比使用PFS产生的絮体快;絮体结构为内部有较多内孔的网状结构,内孔的可渗透性可降低沉降阻力,提高沉降速度.图5,参9.     

Zn(Ⅱ)-(NH4)2SO4-H2O体系浸出锌烟尘

提出硫酸铵浸出法处理锌烟尘的新工艺。该工艺利用不同温度下锌在硫酸铵溶液中的溶解度的差别,先在高温下将锌浸入溶液然后降温冷却,使锌呈含F和Cl很低的复盐析出,然后回收。以株冶集团锌烟尘为试料,对浸出过程进行研究。研究结果表明:浸出温度和硫酸铵浓度显著影响锌的浸出率;最佳浸出条件是:液固比为16?1,硫酸铵浓度为4.0 mol/L,pH值为5.5,浸出温度为90℃,浸出时间为4 h,在该条件下,按渣含锌计算的浸出率达到85.16%。     

3a0．6Sr0．4TiO3／MgO／Mg2SiO4复相陶瓷的制备与介电可调性能

采用标准电子陶瓷工艺，制备了Ba0．6Sr0．4TiO3／MgO／Mg2SiO4复相陶瓷（MgO和Mg2SiO4按相同重量加入），研究了MgO和Mg2SiO4含量对复相陶瓷微观结构、介电性能及介电可调性的影响．结果表明，随着MgO和Mg2SiO4含量的增加，陶瓷的晶粒尺寸略有增大，低频（100kHz）介电常数、介电损耗、介电可调度和介电常数温度系数降低．随着偏置电场的增强，介电常数降低，介电损耗变化不大（均在10^-3量级）．当MaO和Mg2SiO4的百分含量均为30％时，获得了室温介电常数为101．6、介电损耗为0．0017及1．79kV／mm偏置电场下介电可调度为12．19％、介电常数温度系数为0．009℃^-1的介电性能。     

胶束增敏荧光光度法测定甲氧氯普胺的研究

本文用荧光光度法对酸性介质中甲氧氯普胺和十二烷基硫酸钠形成的胶束配合物的性能进行了系统研究。利用胶束的增敏增稳作用，提出了测定甲氧氯普胺的荧光光度新方法。本法线性范围宽，为１．３×１０－８～８．０×１０－６ｍｏｌ·Ｌ－１，灵敏度高，检出限为１．２×１０－８ｍｏｌ·Ｌ－１。应用本法于样品中甲氧氯普胺的测定，平均回收率为９８．８％，结果令人满意。     

利用CT扫描仪分析不同类型BaSO4对X射线的衰减规律

提出了一种利用CT扫描仪分析不同类型、不同细度的硫酸钡对X射线的衰减能力的新方法，分析讨论了不同类型、不同细度的硫酸钡对X射线的衰减规律和衰减原因，为检测筛选高效能的新型医用硫酸钡提供了一种更加科学、简便的方法．