高效液相色谱法测定鼠脑谷氨酸脱羧酶活性

应用高效液相色谱-电化学检测技术建立了鼠脑谷氨酸脱羧酶(GAD)活性的测定方法.方法快速,灵敏.总分析时间为9min.γ-氨基丁酸的最低柱上检测限为50fmol.天内及天间相对标准差分别小于4.3%和9.8%.测得CAD最大催化速率为0.723nmol/min/mg蛋白.讨论了最佳衍生化pH及色谱条件.     

微量热法研究环境NaCl浓度对盐生盐杆菌生长代谢的影响

采用TAM air微量热系统和安瓿法测定了盐生盐杆菌在不同NaCl浓度中生长的生长产热曲线, 拟合得到盐生盐杆菌在不同NaCl浓度中生长的热动力学方程和热动力学参数, 并分析了盐生盐杆菌生长的各种热动力学参数与环境NaCl浓度的关系. 由此发现, 盐生盐杆菌生长的最适NaCl浓度并不是传统认为的一个宽泛的范围——3.5 mol·L^-1至约5.2 mol·L^-1 (NaCl饱和), 而是约3.9 mol·L^-1. 在环境NaCl浓度由3.9 mol·L^-1逐步升高至饱和的过程中, 盐生盐杆菌的生长代谢持续减弱. 进一步的透射电镜观察发现在近饱和的NaCl浓度中生长的盐生盐杆菌细胞发生了质壁分离, 较好地解释了微量热研究的结果. 由此对NaCl浓度变化导致嗜盐古生菌表面结构改变提出了新的解释.     

铅对海马神经元通道、受体和递质的影响及作用机制

综述了铅影响儿童学习记忆毒理机制研究的部分进展,即铅对海马神经元通道、受体和递质的影响及作用机制,包括铅对海马突触可塑性,离子通道,对NMDA受体、非NMDA受体及通道特性,神经递质和基因调控的影响。参考文献27篇。     

交换时间对离子交换法合成谷氨酸/锌铝层状双氢氧化物的结构和热稳定性的影响

采用离子交换法实现了谷氨酸(Glu)插层到ZnAl层状双氢氧化物(ZnAl-LDH)中而形成Glu/ZnAl-LDH纳米复合材料,并用X射线衍射(XRD)、傅里叶变换红外(FT-IR)光谱、透射电子显微镜(TEM)以及热失重-差热(TG-DTA)分析等测试技术,研究了交换时间对Glu/ZnAl-LDH纳米复合材料结构的影响。发现当交换时间为1d时,Glu/ZnAl-LDH纳米复合材料粒子的结晶度好,Glu分子均以垂直形式插入,此时Glu在层间达到交换平衡。当交换时间为2d时,部分Glu开始以水平方式插入ZnAl-LDH纳米材料层间。但当交换时间进一步延长时,ZnAl-LDH纳米材料的结构发生部分坍塌,而且ZnAl-LDH纳米材料在微酸性的Glu溶液中发生部分溶解而使其六边形的结构出现破损。由于Glu插入ZnAl-LDH纳米复合材料层间后,其稳定性得到提高,因此,ZnAl-LDH纳米材料可以作为优良的生物分子的载体和储存器。     

外来水分对煤自燃过程影响及作用机制研究

通过浸泡方法制备一系列不同外来水分含量的煤体,利用程序升温氧化实验模拟煤自燃过程,研究外来水分对煤自燃特性的影响;结合热分析和孔结构表征实验,探讨外来水分对煤自燃过程影响作用机制。外来水分对煤自燃过程的作用机制随着煤自燃状态发展而发生变化,主要表现出四个阶段。在缓慢氧化阶段,外来水分主要隔离煤与氧气的接触反应,对煤自燃起到物理抑制作用;在加速氧化阶段,水分可直接参与煤氧反应,起到化学促进作用;经过缓慢氧化阶段和加速氧化阶段,大量外来水分的蒸发导致煤颗粒表面裂隙增大,水分越大的煤生成的活性点位会更多,当煤自燃进入快速氧化阶段,外来水分对煤氧化反应的影响表现出延迟促进效应;当煤体温度达到180℃后,随着煤体温度进一步升高,不同初始外来水分含量的煤体自燃特征逐渐趋于一致。     

电荷密度和疏水性对疏水改性聚丙烯酰胺与牛血清蛋白相互作用的影响

对比研究了牛血清蛋白(BSA)与部分水解的未改性聚丙烯酰胺(PAM-AA)、疏水改性聚丙烯酰胺(PAM-C12)和含有丙烯酸基团的疏水改性聚丙烯酰胺(PAM-C12-AA)之间的相互作用.等温滴定量热实验结果表明,除PAM-C12外,其他聚合物与BSA的结合焓均为放热,随AA含量的增加,放热焓值增大.与PAM和PAM-C12相比,PAM-C12-AA能够诱导BSA二级结构和微环境的明显变化,表明疏水性和电荷密度均对聚合物与BSA相互作用有重要影响.另外,不同浓度的PAM-C12-AA与BSA的作用方式不同,当聚合物的浓度略高于临界胶束浓度(CMC)时,由于聚合物的量较少,BSA分子改变其构型从而最大程度地与聚合物结合;当聚合物的浓度远高于CMC时,更多的聚合物链结合到BSA分子的正电荷"patch"上,PAM-C12-AA与BSA的紧密聚集体利于BSA二级结构的稳定.     

疏水作用色谱中流动相组成对溶质保留行为的影响

 首次研究了疏水作用色谱 (HIC)中芳香醇同系物在不同种类盐流动相中的保留行为。以计量置换保留模型中的参数Z分析了HIC中小分子与生物大分子保留行为的差别 ,以及不同流动相组成对两种类型溶质的洗脱范围及洗脱能力的影响。与反相色谱相似 ,芳香醇在HIC中的保留仍存在同系物规律。比较了小分子和生物大分子在不同盐溶液中的Z值变化 ,表明流动相中的盐仅改变小分子与固定相的水合程度 ,而对生物大分子 ,除改变其和固定相水合程度外 ,还会影响生物大分子与固定相接触区的分子构象     

静电和疏水效应对TGEV主蛋白酶二聚体稳定性的影响

从TGEV 3CL蛋白酶二聚体结构出发,研究了TGEV 3CL蛋白酶二聚体单体之间的静电和疏水相互作用.蛋白质的静电相互作用通过有限差分方法求解Poisson-Boltzmann方程得到,疏水相互作用通过分析溶剂可及性表面模型得到.考察了不同pH值对TGEV 3CL蛋白酶二聚体静电和疏水相互作用的影响,在pH值为5.5～8.5时,二聚体静电相互作用能、静电去溶剂化能和疏水自由能都较小,表明在该条件下静电和疏水相互作用有利于二聚体的稳定存在,这符合实验结晶所需条件.pH值对静电去溶剂化能的影响大于疏水自由能,表明静电作用是造成强酸或强碱条件下二聚体不能稳定存在的主要原因.     

静电和疏水效应对SARS冠状病毒3CL蛋白酶二聚体稳定性的影响

从TGEV3CL蛋白酶二聚体结构出发,研究了TGEV3CL蛋白酶二聚体单体之间的静电和疏水相互作用.蛋白质的静电相互作用通过有限差分方法求解Poisson-Boltzmann方程得到,疏水相互作用通过分析溶剂可及性表面模型得到.考察了不同pH值对SARS3CL蛋白酶二聚体静电和疏水相互作用的影响,在pH=5.5～8.5时,二聚体静电相互作用能、静电去溶剂化能和疏水自由能都具有较小的数值,表明在该条件下静电和疏水相互作用有利于二聚体的稳定存在.由于SARS3CL蛋白酶活性模式为二聚体,因此,在该pH值范围内,有利于蛋白酶保持活性.在pH=7.0条件下,蛋白酶单体之间具有最强的静电和疏水相互作用,从而使蛋白酶具有最强的活性,这与实验结果相一致.pH值对静电去溶剂化能的影响大于疏水自由能,表明静电作用是造成强酸或强碱条件下二聚体不能稳定存在的主要原因.     

聚γ-谷氨酸对气相色谱-质谱检测地衣芽孢杆菌胞内代谢物的影响

通过添加外源聚γ-谷氨酸(γ-PGA),利用气相色谱-质谱法(GC-MS)评估了γ-PGA对地衣芽孢杆菌胞内代谢物检测的影响。结果表明:终浓度为10g/L的γ-PGA会使除谷氨酸外的氨基酸、有机酸和糖类标准品的检测峰面积明显降低;另外,终浓度为10g/L的γ-PGA对分析地衣芽孢杆菌胞内代谢物中的谷氨酸、葡萄糖和6-磷酸葡萄糖(G6P)的影响较为显著。因此,在利用GC-MS定量分析地衣芽孢杆菌的胞内代谢物前,应将γ-PGA和细胞分离。     

Hydrophobic interaction chromatography at low salt concentration for the capture of monoclonal antibodies

We evaluated hydrophobic interaction chromatography (HIC) at low salt concentration for the capture of proteins from feed stocks by using monoclonal antibodies as model samples. It was indicated that the HIC at low salt concentration on critical hydrophobicity supports has a potential for capturing hydrophobic monoclonal antibodies directly from large volumes of feed stocks and recovering bound monoclonal antibodies in high yield. On the other hand, the HIC at low salt concentration did not seem so useful for the capture of weakly hydrophobic monoclonal antibodies. The recovery of weakly hydrophobic monoclonal antibodies from columns packed with critical hydrophobicity supports was not quantitative and significantly decreased as the residence time of the monoclonal antibodies in the columns became longer.     

Comparison and evaluation of HIC columns of different hydrophobicity

Summary Retention and selectivity in hydrophobic interaction chromatography (HIC) depend both on the type of stationary phase and on the mobile phase. In the last few years various high performance packing materials and columns have been introduced for HIC resulting in a range of different retentions and selectivity. We have investigated the effect of the stationary phase on the retention of various proteins. The retention of some solutes of different hydrophobicities were measured on three commercial HIC columns (TSK-Phenyl, Synchropack-Propyl, CAA-HIC) under isocratic conditions using water-methanol mixtures as eluent. The log k_w values determined according to the literature were devalues determined according to the literature were dependent on the type and structure of the stationary phase and indicated a much less hydrophobic character for these columns than that obtained for reversed phase columns. Gradient separations were then carried out on a standard protein mixture using ammonium sulfate and sodium citrate to change the gradient time. In order to compare the effect of the stationary phase and the two salts investigated apparent capacity factors (k_g) were determined and plotted against the gradient time obtained for the three columns in the two eluent system. It was shown that the type of stationary phase had a significant effect on the retention of proteins. In addition, the effect of the mobile phase composition, i.e. salt type, was considerably different on the various stationary phases. In order to exploit the potential of HIC to modulate selectivity for the separation of proteins, the combined effect of the stationary phase and the type of salt should be taken into account.Dedicated to Professor Leslie S. Ettre on the occasion of his 70th birthday.     

聚皂的性质和研究进展

较系统地综述了聚皂的性质和研究进展,侧重介绍了近年来利用荧光探针技术研究聚皂在水溶液中的聚集特性,以及利用紫外／可见光探针技术,从动力学催化反应、与甲基橙的相互作用来研究聚皂形成胶束的机理及结构。同时介绍了聚皂在某些些方面的应用。     

Characterization and modeling of nonlinear hydrophobic interaction chromatographic systems

A general rate model was employed in concert with a preferential interaction quadratic adsorption isotherm for the characterization of HIC resins and the prediction of solute behavior in these separation systems. The results indicate that both pore and surface diffusion play an important role in protein transport in HIC resins. The simulated and experimental solute profiles were compared for two model proteins, lysozyme and lectin, for both displacement and gradient modes of chromatography. Our results indicate that a modeling approach using the generate rate model and preferential interaction isotherm can accurately predict the shock layer response in both gradient and displacement chromatography in HIC systems. While pore and surface diffusion played a major role and were limiting steps for proteins, surface diffusion was seen to play less of a role for the displacer. The results demonstrate that this modeling approach can be employed to describe the behavior of these non-linear HIC systems, which may have implications for the development of more efficient preparative HIC separations.     

RAPID DETERMINA TION OF L—GLUTAMIC ACID WITH AN ENZYME REACTOR OFL—GLUTAMIC DECARBOXYLASE IMMOBILIZED ON ION EXCHANGE RESIN

The preparation and characterization of an immobilized L-glutamic decarboxylase(GDC) were studied.This work is to develop a sensitive method for the determination of L-glutamate using a new biosensor,which consists of an enzyme column reactor of GDC immobilized on a novel ion exchange resin(carboxymethyl-copolymer of allyl dextran and N.N‘-methylene-bisacrylamide CM-CADB) and ion analyzer coupled with a CO2 electrode.The conditions for the enzyme immobilization were optimized by the parameters:buffer composition and concentration,adsorption equilibration time,amount of enzyme,temperature,ionic strength and pH.The properties of the immobilized enzyme on CM-CADB were studied by investigating the initial ate of the enzyme reaction,the effect of various parameters on the immobilized GDC activity and its stability.An immobilized GDC enzyme column reactor matched with a flow injection system-ion analyzer coupled with CO2 electrode-data collection system made up the original form of the apparatus of biosensor for determining of L-glutamate acid.The limit of detection is 1.0×10^-5M.The linearity response is in the range of 5×10^-2-5×10^-5M.The equation of linear regression of the calibration curve is y=43.3x+181.6(y is the milli-volt of electrical potential response,x is the logarithm of the concentration of the substrate of L-glutamate acid).The correlation coefficient equals 0.99.The coefficient of varioation equals 2.7%.     

Clouding behavior of nonionic–cationic and nonionic–anionic mixed surfactant systems in presence of carboxylic acids and their sodium salts

The study is focused on evaluation of clouding phenomena of the aqueous single nonionic surfactant system Triton X-100 (TX-100) and its mixed systems with anionic aerosol-OT (AOT) and cationic dodecylpyridinium chloride (DPC) in presence of hydrophobic ions furnished by sodium salts of carboxylic acids, viz., sodium ethanoate, sodium propanoate, sodium butanoate, and sodium hexanoate and the respective carboxylic acids [ethanoic acid, propanoic acid, butanoic acid, and hexanoic acid]. The influence of salts on the cloud point (CP) has been explained on the basis of salt effect as well as the solubilization of higher alkyl chain hydrophobic ions furnished by these salts. Moreover, the co- and counterion effect has been taken into account to explain the variation of the CP in the mixed systems. However, the effect of acids on CP has been explained in the light of their aqueous solubility and their partitioning ability between octanol and water as reflected by their K _OW values.     

Neural Network Learning of the Interaction Between Peptide Segments of Proteins

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