Differentiation of peptide molecular recognition by phospholipase C gamma-1 Src homology-2 domain and a mutant Tyr phosphatase PTP1bC215S.

Activated epidermal growth factor receptor (EGFR) undergoes autophosphorylation on several cytoplasmic tyrosine residues, which may then associate with the src homology-2 (SH2) domains of effector proteins such as phospholipase C gamma-1 (PLC gamma-1). Specific phosphotyrosine (pTyr)-modified EGFR fragment peptides can inhibit this intermolecular binding between activated EGFR and a tandem amino- and carboxy-terminal (N/C) SH2 protein construct derived from PLC gamma-1. In this study, we further explored the molecular recognition of phosphorylated EGFR988-998 (Asp-Ala-Asp-Glu-pTyr-Leu-Ile-Pro-Gln-Gln-Gly, I) by PLC gamma-1 N/C SH2 in terms of singular Ala substitutions for amino acid residues N- and C-terminal to the pTyr (P site) of phosphopeptide I. Comparison of the extent to which these phosphopeptides inhibited binding of PLC gamma-1 N/C SH2 to activated EGFR showed the critical importance of amino acid side chains at positions P+2 (Ile994), P+3 (Pro995), and P+4 (Gln996). Relative to phosphopeptide I, multiple Ala substitution throughout the N-terminal sequence, N-terminal sequence, N-terminal truncation, or dephosphorylation of pTyr each resulted in significantly decreased binding to PLC gamma-1 N/C SH2. These structure-activity results were analyzed by molecular modeling studies of the predicted binding of phosphopeptide I to each the N- and C-terminal SH2 domains of PLC gamma-1.(ABSTRACT TRUNCATED AT 250 WORDS)     

Crystal structure of thioltransferase at 2.2 A resolution.

We report here the first three-dimensional structure of a mammalian thioltransferase as determined by single crystal X-ray crystallography at 2.2 A resolution. The protein is known for its thiol-redox properties and dehydroascorbate reductase activity. Recombinant pig liver thioltransferase expressed in Escherichia coli was crystallized in its oxidized form by vapor diffusion technique. The structure was determined by multiple isomorphous replacement method using four heavy-atom derivatives. The protein folds into an alpha/beta structure with a four-stranded mixed beta-sheet in the core, flanked on either side by helices. The fold is similar to that found in other thiol-redox proteins, viz. E. coli thioredoxin and bacteriophage T4 glutaredoxin, and thus seems to be conserved in these functionally related proteins. The active site disulfide (Cys 22-Cys 25) is located on a protrusion on the molecular surface. Cys 22, which is known to have an abnormally low pKa of 3.8, is accessible from the exterior of the molecule. Pro 70, which is in close proximity to the disulfide bridge, assumes a conserved cis-peptide configuration. Mutational data available on the protein are in agreement with the three-dimensional structure.     

Protein recognition of ammonium cations using side-chain aromatics: a structural variation for secondary ammonium ligands.

A model for the structure of dimethylamine dehydrogenase was generated using the crystal coordinates of trimethylamine dehydrogenase. Substrate is bound in trimethylamine dehydrogenase by cation-pi bonding, but modeling of dimethylamine dehydrogenase suggests that secondary amines are bound by a mixture of cation-pi and conventional hydrogen bonding. In dimethylamine dehydrogenase, binding is orientationally more specific and distinct from those proteins that bind tertiary and quaternary amine groups.     

罗汉果胚、胚乳及胚乳吸器的发育

本文采用石蜡切片与酶解分离法对罗汉果Ｓｉｒａｉｔｉａｇｒｏｓｖｅｎｏｒｉ胚、胚乳及胚乳吸器的发育过程进行观察．ａ）罗汉果胚的发育是按Ｇｅｕｍｕｒｂａｎｕｍ的分裂程序进行的．属紫菀型．但在合子分裂成球胚过程中,胚芽原细胞分化明显．故属紫菀型的变异型。ｂ）胚乳发育属核型．在球形胚阶段,在合点端和珠孔端有发育的胚乳吸器形成并进行旺盛生长,最大长度达１４２０μｍ,心形胚期．吸器活动开始减退,合点端核型胚乳吸器转变成细胞型．由胚乳本体基部膨大细胞．充当补助吸器．ｃ）酶解分离法研究胚乳吸器的发生发育有较好的应用前景。     

中国粗叶本属（茜草科）的植物地理研究

本文研究了中国产粗叶本属植物３０种４亚种和７变种的地理分布,划分出三个分布区类型,十二个变型和四个亚变型。根据种多度和分布特征,中国粗叶本属植物在分布上表现出与中国的热带雨林、季雨林区,南亚热带常绿阔叶林带和中亚热带常绿阔叶林带相匹配的分布规律,并受几条植物地理界线的作用。通过对地理替代类群和一些特殊分布式样的分析,显示了所谓的“田中线”和一条北起四川峨眉向南经贵州西南部至广西西部的界线对粗叶木种的分布,特别是对中国－喜马拉雅和中国－日本替代分布具有明显的作用。这导致笔者认为“田中线”作为中国－日本分布的西界而另一第线作为中国－喜马拉雅分布的东界。进一步的分析还揭示由云南南部沿缅甸、泰国向南延伸的横断山余脉既充做一条植物南－北迁移的通道又是一条中南半岛西部（印－缅）与东部（印度支那－华南）的植物地理界线。     

互叶白千层油化学成分的研究

采用水蒸汽蒸馏收集互叶白千层芳香油,对该油进行ＧＣ／ＭＳ／ＤＳ定性分析及其总离于流图的面积归一化定量分析,鉴定出２５种化合物,其中含氧化合物６种,碳氢化合物１９种。直接影响该油商品价值的化学成分４－萜品醇含量约为１７％,桧樟脑含量约为２．４％。     

四川地区幼儿和学龄前儿童的鼻部测量

本文报告１１１６例四川地区幼儿和学龄前儿童（２－７岁）鼻部９项指标的测量均数,性差及年龄发育特点。性差：仅鼻凹鼻底距４－６．５岁等少数指标部分年龄段男女性间出现显著性划异（男＞女）。此外各项指标的绝大多数年龄段男女性间无显著性差异。年龄发育：９项测量指标中７项的生长曲线随年产长而上升,数值随年龄增大,并有１－２个发育高峰;提示鼻部发育具有阶段性;２项指标的曲线随年龄增长变化较小。４项指标男女性的曲     

裂褶菌多糖的构象研究

从裂褶菌中提取一水溶性多糖Sci.气相色谱,高碘酸盐氧比,甲基化分析等确定它为葡聚糖.1-3糖苷键构成其主链,平均三分之一的主链残基在6位带有分枝,红外光谱和三氧化铬氧化表明Scl全部残基为β构型,在不同的温度和不同的酸碱浓度状态下,检查糖链与刚果红形成络合物的能力以及Scl水溶液的粘度和旋光值.推测低温近中性Scl主要呈单股螺旋构象.升温或提高酸碱浓度导致有规则的螺旋构象转变成无规则的线团.高碘酸盐氧化去掉分枝则多股螺旋比例在构象中增加.     

拉萨郊区藏族的指纹研究

本文报道了拉萨郊区５１７例（男２２６人,女２９１人）藏族健康人的指纹参数正常值、调查分析了指纹类型、指纹组合、指纹指数和指嵴纹计数。比较了藏族不同居群、不同民族和人种间的差异。结果表明,藏族有自己的指纹特点,又显著蒙古人种的一般特征。     

蛋白质特异性断裂试剂研究进展

蛋白质特异性断裂试剂是近年来发展起来的一些具有特异性断裂肽键功能的化学工具．这些断裂试剂可分为两类,一类通过氧化断裂机制实现蛋白空间结构特异性切割,另一类通过水解断裂机制实现序列特异性切割．蛋白质特异性断裂试剂在蛋白质序列测定,蛋白质的结构与功能研究,蛋白质与核酸相互作用研究以及新型化学治疗药物的合成等方面有着广阔的应用前景．