酶蛋白分子可及性与等电点关系的研究

依据酶的晶体结构数据对它的分子可及性进行了计算和分析 ,探讨了氨基酸可及性与酶性质的关系 ,研究了氨基酸可及性和酶等电点之间的关系 ,发现了氨基酸可及性与酶等电点之间的线性关系。     

关于氨基酸溶液的酸碱性及等电点计算问题的说明

氨基酸为两性化合物,以内盐形式存在,其水溶液的pH值与其等电点(PI)相等。可用其解离常数通过有关计算式计算出氨基酸的等电点。     

酶、多肽电荷数的理论计算及误差研究

对酶的电荷数随ｐＨ变化的定量关系进行了理论推导,将推导出的酶的电荷数与ｐＨ的关系式应用于多肽等电点的计算,理论计算结果与文献实验结果完全一致,并推导出酸性氨基酸、碱性氨基酸及中性氨基酸等电点的计算式,与现有计算式完全一致．应用荧光光谱和荧光偏振对肌酸激酶带电性随ｐＨ值的变化关系的研究表明,理论计算符合实验结果,表明：此文理论关系式是可靠的．     

酸碱性氨基酸的离子交换行为

本文叙述和讨论了酸碱性氨基酸的离子交换行为。在等电点 pH 范围内吸附的氨基酸量最大,它和中性氨酸基比较起来,pH 的影响是极为特殊的。本文还从理论上论述了离子交换平衡、氨基酸离解平衡、解释了实验结果,并由此推算出选择性系数。     

海洋游仆虫细胞核染色质组分和组蛋白的初步研究

收集海洋游仆虫(Euplotes vannus)的细胞,制备其染色质。稀酸抽提染色质得到的组蛋白经聚丙烯酰胺凝胶电泳、SDS-聚丙烯酰胺梯度凝胶电泳、等电点聚焦和氨基酸分析等方法测定,其核染色质中组蛋白占核总蛋白的69.6％;DNA:RNA:组蛋白:非组蛋白为1∶0.022∶1.1∶0.047。染色质的全组蛋白由16种氨基酸组成,碱性氨基酸与酸性氨基酸之比为1.06∶1,是一种弱碱性蛋白质。等电点为pH8.1—9.15,分子量为10,500—22,000道尔顿。     

人胎盘催乳素多型性研究

通过纯化和分析人胎盘催乳素,发现其有两个等电点,与文献报道不一致,利用等电聚焦制备电泳分离了两个等电点组分。免疫学活性测定的结果表明,两个组分均有活性,且活性有差别,等电点高的组分,免疫学活性强。通过Ｎ端氨基酸分析发现,两组分的Ｎ端均为缬氨酸。推测人胎盘催乳素存在亚型,为进一步研究人胎盘催乳素的结构和功能以及临床上正确地利用此激素提供了有价值的依据。     

人胎盘催乳素多型性研究

通过纯化和分析人胎盘催乳素,发现其有两个等电点,与文献报道不一致,利用等电聚焦制备电泳分离了两个等电点组分,免疫学活性测定的结果表明,两个组分均有活性,且活性有差别,等电点高的组分,免疫学活性强,通过Ｎ端氨基酸分析发现,两组分的Ｎ端均为缬氨酸,推测人胎盘催乳素存在亚型,为进一步研究人胎盘催乳素的结构和功能以及临床上正确地利用此激素提供了有价值的依据。     

氨基酸的分子结构与遗传密码简并及二维集合分类

根据氨基酸遗传密码子的简并程度,可将64个遗传密码子分为高简并度类（3,4,6度简并组）和低简并度类（1,2度简并组）两大类。高简并度类有9个氨基酸,其分子量比较小,等电点的分布比较集中。低简并度类有11个氨基酸,其分子结构比较复杂,参考Taylor对氨基酸特性的分类图,本文提出以分子量（M）及等电点（P）作为氨基酸的化学特性坐标,作出其二维集合MP分类图,MP分类图可以反映出氨基酸的各种属性,如分子量的大小,简并度的高低,极性与非极性、带电荷或不带电荷,疏水性与亲水性,以及氨基酸残基的种类等。根据氨基酸的分类分析,可以认为：高简并度氨基酸多数是脂烃类和羟脂烃类的氨基酸,分子量比较小,分子结构比较简单,大部分为疏子性,主要组成跨膜结构或蛋白质的结构域,可能是出现较早的氨基酸;而低简并度的氨基酸,分子结构比较复杂,分子量比较大,多数是和蛋白质功能有密切联系的基团,可能是进化出现较晚的结构。     

印度木薯花叶双生病毒外壳蛋白的研究Ⅱ．计算机分析外壳蛋白的一些特性

用NWGCG软件系统分析了印度木薯花叶双生病毒外壳蛋白的一些性质：(1)外壳蛋白是碱性蛋白,其等电点为10．91;(2)在外壳蛋白氨基酸序列中分布有α—helcies,β—Sheets及turns等二级结构;(3)分析了外壳蛋白中可能的表面氨基酸区域,亲水性和抗原决定簇区域;(4)在外壳蛋白的氨基酸序列中存在两个糖基化位点HNT,同时分析了双生病毒外壳蛋白氨基酸遗传密码的利用频率。     

富硒灵芝硒蛋白(Se-GL-P)生化性质的初步分析

作为阐明一种从富硒灵芝中得到的蛋白(Se-GL-P)结构与功能关系的基础性工作,Se-GL-P的结构在此得到了初步表征.分子质量通过电泳和分子筛两种方法进行了测定,通过高效液相色谱、毛细管等电聚焦电泳、原位胶内酶切和Edman降解等方法分别测定了蛋白质的氨基酸组成、等电点、肽图以及N端氨基酸序列等方面的性质,并对其同源性进行了鉴定.结果表明,该蛋白质的相对分子质量为36600,等电点为4.01,N端20个氨基酸序列为DINGGGATLPQKLYLTPDVL.实验得到结论:Se-GL-P是一种新的硒蛋白,并属于功能性DING蛋白家族的一员.     

Purification and properties of staphylocoagulase.

Staphylocoagulase, an exoprotein of coagulase-positive Staphylococci, has been purified to a state in which only trace amounts of contaminating proteins are detectable. Aspartic acid was found as a single N-terminal amino acid in this preparation. The molecular weight is 61 000; the isoelectric point lies as pH 4.53. The amino acid composition was determined.     

Complete Amino Acid Sequence of a Polypeptide from Zea mays Similar to the Pathogenesis-Related-1 Family

A polypeptide serologically related to the tobacco pathogenesis-related-1 family of proteins has been purified from the root tissue of maize (Zea mays L.), and the complete amino acid sequence has been determined. The mature protein has a calculated molecular weight of 14,970 and isoelectric point of 4.2. The maize protein shows 66 to 68% amino acid identity with the tobacco pathogenesis-related-1 family and 55% identity with the tomato p14 protein.     

猪肠毒素源性大肠杆菌K88ac粘附抗原的核苷酸序列分析

 本文对国内流行的猪肠毒素源性大肠杆菌K88ac抗原的结构基因的核苷酸序列进行了测定。该基因由849对核苷酸组成,编码了283个氨基酸的蛋白亚单位及21个氨基酸的信号肽。与国外报道的K88ac序列的不同是我们发现一个碱基的点突变,导致在抗原决定簇内一个氨基酸的改变。从核苷酸序列推导出的氨基酸序列与另两种亚型进行了比较。     

Characterization of cytoplasmic arginine-rich basic protein of Guerin epithelioma

Summary Arginine-rich basic protein from cytoplasma of Guerin epitheliomas has been isolated and characterized. It contains five amino acids: arginine, lysine, glycine, alanine and glutamic acid which make together 74 per cent of all amino acid residues. The protein has a cationic character with an isoelectric point of 8.2. No carbohydrate component was found in this protein. The significance of arginine-rich basic protein in the cytoplasma of Guerin epithelioma is discussed briefly.     

Molecular characterization of ura1, a mutant allele for orotidine-5'-monophosphate decarboxylase in Schizophyllum commune

Abstract The basis of the auxotrophic ural phenotype in Schizophyllum commune has been investigated. Two point mutations causing changes in conserved amino acid positions 62 (from lysine to glutamate) and 79 (from leucine to phenylalanine) most likely are the cause for the observed phenotype, whereas the overall gene structure was unchanged. Since reversion rates in this locus are extremely low, a single point mutation could not be expected to be the cause for the mutation. Besides the two point mutations expected to be induced by UV mutagenesis, the two alleles investigated from independently isolated strains differ by approximately 7% in nucleic acid sequence and about 3% in amino acid sequence, indicating a distant relationship between the strains used.     

Nucleotide sequence of the gene ompA coding the outer membrane protein II of Escherichia coli K-12.

A nucleotide sequence of 2271 basepairs has been determined from cloned E. coli DNA which contains ompA. Withing that sequence, starting at nucleotide 1037, an open translational reading frame encodes a protein of 367 amino acids which starting with amino acid 22 agrees with the primary structure of protein II. The preceeding 21 amino acids constitute a typical signal sequence. There is a non-translated region of 360 nucleotides in front of the translational start. The insertion point of an IS1 element 110 nucleotides upstream from the start codon and an amber codon at the position of amino acid residue 28 have been localized in the DNA from two ompA mutants.     

Complete amino Acid sequence of soybean leaf p21 : similarity to the thaumatin-like polypeptides

A polypeptide structurally related to the thaumatin family of proteins has been purified from soybean (Glycine max) leaves and the complete amino acid sequence has been determined. The mature protein, which we have termed P21, has a calculated molecular weight of 21,461 and an isoelectric point of 4.6. The soybean protein shows 64% amino acid identity with thaumatin, a sweet-tasting protein found in the West African shrub Thaumatococcus danielli, and as much as 71% identity with thaumatin-like polypeptides present in tobacco and maize.     

Physicochemical characterization of pituitary follicle-stimulating hormone

The physiochemical characteristics of the follicle-stimulating hormone (FSH) from whole sheep pituitary glands have been studied. The hormone behaves as a single protein in electrophoresis, diffusion, and ultracentrifugation. It has an isoelectric point at pH 4.5 and a molecular weight of 67,000 and contains 1.23 per cent hexose and 1.51 per cent hexosamine. The amino acid composition has also been determined in large part. The stability of the hormone to acid and heat has been investigated.     

Some properties of phosphatidylcholine exchange protein purified from beef liver

A phospholipid exchange protein has been purified 2680-fold from beef liver. The assay of the exchange activity of the protein was based on the transfer of [¹⁴C]phosphatidylcholine from microsomes labeled with [¹⁴C]phosphatidylcholine to liposomes. The homogeneity of the protein has been established by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, immunoelectrophoresis and isoelectric focusing. The protein has a molecular weight of approximately 22000 and an isoelectric point of 5.8. The amino acid composition has been determined. The protein contains one disulfide bridge and has glutamic acid as the N-terminal amino acid. Phospholipid, tentatively identified as phosphatidylcholine, was found to be present in the protein preparation. The protein stimulated specifically the exchange of phosphatidylcholine between mitochondria and microsomes from rat liver.     

Code of codon roots, determining the intra- and intermolecular interaction of amino acids in peptide chains]

To study the recognition processes and interaction of peptides and proteins, a model has been suggested according to which the first steps of complex formation of molecules are defined by G/C and A/U complementarity of codon roots of amino acid forming the molecules contact sites or surfaces. In contrast to amino acid--antiamino acid interaction code (L. B. Mekler, 1969), the code of codon roots involves the interaction of amino acids independently of the base structures in nucleotide triplets in positions 1 and 3. The analysis of the spectra of point mutations homologous proteins confirms the possible role of the root code.