应用蛋白质组学方法研究盐角草（Salicornia europaea L.）的抗盐性-盐角草双向电泳体系的建立

盐角草（Salicornia europaea L.）是世界上最抗盐的高等植物之一。应用蛋白质组学方法对其抗盐性进行研究，对于我们理解植物抗盐机理和改进作物耐盐性都有重要意义。双向电泳是蛋白质组学的核心技术，样品制备是双向电泳的关键步骤。盐角草是一种聚盐的真盐生高等植物，其体内除含有多种次生代谢物质外还含有大量盐分，而盐离子的存在严重干扰等电聚焦的进行，其蛋白质提取较其他植物更为困难。因此，在进行蛋白质组学研究之前，有必要对其蛋白质提取方法进行摸索，建立一个高效的双向电泳体系。 　　比较了三氯乙酸/丙酮沉淀法（TCA）、三氯乙酸沉淀法（E-TCA）和酚抽法（Phe）三种方法对盐角草蛋白的提取效果。提取700mM处理2d的盐角草幼苗蛋白时，三种方法分别得到579，343和535个蛋白点;TCA和E-TCA法所得图谱均存在严重的横向纹理，Phe法所得图谱则背景干净，基本上没有纹理。说明Phe法不仅能很好地提取盐角草蛋白，而且能有效去除样品中的盐分。对200mM处理90d的盐角草蛋白的提取也证实了这一点。比较了不同沉淀剂对Phe法蛋白提取效果的影响，结果表明，甲醇不能代替乙酸铵甲醇溶液。对Phe法的提取液进行了改进，所得图谱背景更加清晰，蛋白点数增加。此外，还对聚焦时间，上样量和染色方法进行了改进优化，建立了盐角草双向电泳体系。 　　本研究表明，Phe法适合于盐角草双向电泳样品的制备，这为其他盐生植物以及嗜盐微生物蛋白质的提取提供了重要参考。 　　

The nuclear matrix of Euglena gracilis (Euglenophyta): A stage of nuclear matrix evolution?

Euglena gracilis cell was extracted sequentially with CSK-Triton buffer, RSB-Magik solution and DNase-As solution. DGD embedment-free electron microscopy showed that in the extracted nucleus there was a residual non-chromatin fibrous network. That it could not be removed by hot trichloroacetic acid further supported the idea that it was a non-histone, non-chromatin fibrous protein network, and should be the internal network of the nuclear matrix. After the sequential extraction, the nuclear membrane was removed, leaving behind a layer of lamina; the chromatin was digested and eluted from the dense chromosomes and residual chromosomal structures that should be chromosomal scaffold were revealed. Western blot analysis with antiserum against rat lamins showed that nuclear lamina of the cell possessed two positive polypeptides, a major one and a minor one, which had molecular masses similar to lamin B and lamin A, respectively. Comparing these data with those of the most primitive eukaryote Archezoa and of higher eukaryotes, it was suggested that the lower unicellular eukaryote E. gracillis already had the nuclear matrix structure, and its nuclear matrix (especially the lamina) might represent a stage of evolutionary history of the nuclear matrix. (C) 2000 Editions scientifiques et medicales Elsevier SAS.

Study of competitive binding of enantiomers to protein by affinity capillary electrochromatography

Affinity capillary electrochromatography (CEC) with zonal elution method was used to probe the competitive interactions of enantiomers with protein. In this approach, a known concentration of a competing agent is continuously applied to a CEC column with bovine serum albumin (BSA) physically adsorbed on SAX packing while injections of a small amount of analyte are made. The binding sites of solutes on the BSA molecule were determined by the changes in the retention factors of the solutes resulted from the addition of competitive agent. By using D- or L-tryptophan as competitive agents and D-, L-tryptophan and benzoin enantiomers as injected analytes showed that BSA molecule has a primary site to strongly bind L-tryptophan, but D-tryptophan dose not bind at this site; D- and L-tryptophan share a weak binding site on the BSA molecule. Benzoin enantiomers do not share any binding sites with either D- or L-tryptophan. Non-chiral compounds of trichloroacetic acid and n-hexanoic acid were applied as the competitive agents to study the binding of warfarin enantiomers to BSA, it was observed that trichloroacetic acid and n-hexanoic acid had a same binding site for warfarin enantiomers binding to BSA molecule. (C) 2002 Elsevier Science B.V. All rights reserved.

An Amino Acid Substitution Matrix for Protein Conformation Identification

Amino acid substitution matrices play an essential role in protein sequence alignment, a fundamental task in bioinformatics. Most widely used matrices, such as PAM matrices derived from homologous sequences and BLOSUM matrices derived from aligned segments of PROSITE, did not integrate conformation information in their construction. There are a few structure-based matrices, which are derived from limited data of structure alignment. Using databases PDB_SELECT and DSSP, we create a database of sequence-conformation blocks which explicitly represent sequence-structure relationship. Members in a block are identical in conformation and are highly similar in sequence. From this block database, we derive a conformation-specific amino acid substitution matrix CBSM60. The matrix shows an improved performance in conformational segment search and homolog detection.

Preparation And Tribology Studies of Alkyl Carboxylic Acid Monolayer Films on Pei-Coated Glass Substrate

首次在涂敷PEI的玻璃表面上制备了癸酸及全氟癸酸的单分子层膜。研究了成膜机理及摩擦特性。结果表明。脱水剂DCCD促进了癸酸或全氟癸酸与PEI酞胺化的反应。导致两种羧酸在PEI表面产生了靠化学键（酞胺键）连接的稳定的单分子层膜,摩擦、磨损实验表明。单分子层有机膜的摩擦特性受膜的组成、表面能及有序性和堆积密度的重要影响。表面能越低,有序性和堆积密度越高。摩擦系数越低。与碳氢化合物相比。碳氟化合物形成的有序膜具有更高的强度和抗磨性能。

Preparation and Tribological Studies of Stearic Acid Self-Assembled Monolayers on Polymer-Coated Silicon Surface

We present a good alternative method to improve the tribological properties of polymer films by chemisorbing a long-chain monolayer on the functional polymer surface. Thus, a novel self-assembled monolayer is successfully prepared on a silicon substrate coated with amino-group-containing polyethyleneimine (PEI) by the chemical adsorption of stearic acid (STA) molecules. The formation and structure of the STA-PEI film are characterized by means of contact-angle measurement and ellipsometric thickness measurement, and of Fourier transformation infrared spectrometric and atomic force microscopic analyses. The micro- and macro-tribological properties of the STA-PEI film are investigated on an atomic force microscope (AFM) and a unidirectional tribometer, respectively. It has been found that the STA monolayer about 2.1-nm thick is produced on the PEI coating by the chemical reaction between the amino groups in the PEI and the carboxyl group in the STA molecules to form a covalent amide bond in the presence of N,N'-dicyclohexylcarbodiimide (DCCD) as a dehydrating regent. By introducing the STA monolayer, the hydrophilic PEI polymer surface becomes hydrophobic with a water contact angle to be about 105degrees. Study of the time dependence of the film formation shows that the adsorption of PEI is fast, whereas at least 24 h is needed to generate the saturated STA monolayer. Whereas the PEI coating has relatively high adhesion, friction, and poor anti-wear ability, the STA-PEI film possesses good adhesive resistance and high load-carrying capacity and anti-wear ability, which could be attributed to the chemical structure of the STA-PEI thin film. It is assumed that the hydrogen bonds between the molecules of the STA-PEI film act to stabilize the film and can be restored after breaking during sliding. Thus, the self-assembled STA-PEI thin film might find promising application in the lubrication of micro-electromechanical systems (MEMS).

Effects of Molecular Length, Ortientation and Amino Acid Mutation on Kinetics of Selectin/Ligand interactions

Receptor/ligand interactions are basic issues to cell adhesion, which are important to many physiological and pathological processes such as lymphocyte-mediated cytotoxicity, tumor metastasis and inflammatory reactionl. Selectin/carbohydrate ligand bindings have been found to mediate the fast rolling of leukocytes on activated endothelial monolayer. Kinetic rate and binding affinity constants are essential determinants of cell adhesion...