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。     

PrPC与蛋白质X结合位点可及性的初步探讨

根据PDB提供的PrPC的原子坐标,利用MSMS程序,对PrPC氨基酸残基溶剂可及表面积进行了计算和分析.结果表明:(1) PrPC氨基酸残基可及性具有总体一致性特点;(2) PrPC蛋白质序列中非保守残基与种间屏障有一定关系;(3) 在PrPC向PrP Sc转变过程中,由于蛋白质X的结合,PrPC可能会出现一定的构象变化,这种变化利于PrPC向PrPSc发生转变.     

蛋白质分子立体化学的自动分析——Ⅲ.原子环境分析

这是关于蛋白质分子立体化学自动分析方法报道的第三篇,介绍自动分析原子环境的方法和应用于胰岛素结构所得到的一些结果。现在建立的程序具有多种功能,可以分别给出分子的全部内环境,单纯极性基团的环境,任一氨基酸的环境,以及任意原子基团的环境,还可以单独给出各氨基酸残基的C~α原子之间的距离,作为结构域辨识的参考。对胰岛素分子的计算结果发现,蛋白质分子存在大量弱相互作用,它们对蛋白质的结构和功能都十分重要。     

蛋白质分子立体化学的自动分析——Ⅲ.原子环境分析

这是关于蛋白质分子立体化学自动分析方法报道的第三篇,介绍自动分析原子环境的方法和应用于胰岛素结构所得到的一些结果。现在建立的程序具有多种功能,可以分别给出分子的全部内环境,单纯极性基团的环境,任一氨基酸的环境,以及任意原子基团的环境,还可以单独给出各氨基酸残基的C~α原子之间的距离,作为结构域辨识的参考。对胰岛素分子的计算结果发现,蛋白质分子存在大量弱相互作用,它们对蛋白质的结构和功能都十分重要。     

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。     

伴刀豆球蛋白A-糖复合物的模拟分析

主要分析ConA与不同的糖特异性结合时其活性位点构象变化的特征。模拟分析了ConA糖结合活性中心氨基酸残基结构特征,同时对相应残基原子可及性表面进行了计算和分析。结果表明：（1）ConA在和不同的糖结合时,存在不同的结合方式;（2）不管ConA和什么糖结合,主要的作用是由活性中心的Tyr12、Asn14、Asp208和Arg228提供的;（3）无论是结合单糖还是寡糖,活性中心总是与第一个糖环起主要的结合作用。     

氨基酸残基可及性与蛋白质家族成员结构的保守性

本文在细胞色素ｃ族蛋白和免疫球蛋白家族中一些蛋白质片段的序列比较和分析的基础上,通过计算其氨基酸残基的可及性,对残基可及性与蛋白质序列及其三维结构的保守性之间的关系进行了分析和探讨。结果表明,序列中凡是保守的残基,其可及性都较低,而且这些低可及性的保守性残基与维持蛋白质特有的三维结构相关。作者认为,同一家族的蛋白质中,在进化上相距较远的各成员之间,结构的保守性主要是体现在其三维结构上;序列中的保守     

地衣芽孢杆菌高温α-淀粉酶的组成及光谱学性质

a-Ⅲ是地衣芽孢杆菌变异株A．4041高温a-淀粉酶中的主要组分,每分子含10个钙原子,氨基酸分析表明：a-Ⅲ富含丝氨酸（17．9％）,天门冬氨酸和谷氨酸（包括酰胺）占20．7％,碱性氨基酸占7．7％。紫外光谱的最大和最小吸收分别在278nm和249nm,荧光光谱的最大激发波长和发射波长分别为282nm和340nm。远紫外CD谱显示222nm和219nm的双负峰及208nm和216nm处鼓起的两个负肩,溶液中a-螺旋构象占388％。     

家蚕生物钟蛋白TIME-EA4的进化踪迹分析

家蚕是卵滞育性鳞翅目模式昆虫,其滞育卵的活化与生物钟蛋白TIME-EA4密切相关。TIME-EA4具备稳定的Cu/Zn SOD活性和瞬时的ATP酶活性。目前,国内外关于家蚕TIME-EA4的研究主要集中在结构和功能上,其分子进化机制研究尚未开展。本文利用生物信息学方法对TIME-EA4进行了进化踪迹分析,结果显示TIME-EA4的重要氨基酸残基(coverage25%)的91.2%都用来维持与Cu/Zn SOD的序列一致性,但TIME-EA4与Cu/Zn SOD的Cu/Zn离子结合位点在氨基酸残基组成、极性、绑定原子方面都存在差异。     

地衣芽孢杆菌高温α-淀粉酶的组成及光谱学性质

a-Ⅲ是地衣芽孢杆菌变异株A．4041高温a-淀粉酶中的主要组分,每分子含10个钙原子,氨基酸分析表明：a-Ⅲ富含丝氨酸（17．9％）,天门冬氨酸和谷氨酸（包括酰胺）占20．7％,碱性氨基酸占7．7％。紫外光谱的最大和最小吸收分别在278nm和249nm,荧光光谱的最大激发波长和发射波长分别为282nm和340nm。远紫外CD谱显示222nm和219nm的双负峰及208nm和216nm处鼓起的两个负肩,溶液中a-螺旋构象占388％。     

A homozygous female hemophilia A

BACKGROUND:

Hemophilia A (HA), being an X-linked recessive disorder, females are rarely affected, although they can be carriers.

AIMS:

To study the mutation in F8 gene in an extended family with a homozygous female HA.

MATERIALS AND METHODS:

All the seven affected members (six males and one female) were initially screened by Conformation Sensitive Gel Electrophoresis (CSGE) and direct DNA sequencing.

RESULTS:

A homozygous missense mutation c.1315G>A (p.Gly420Ser) was identified in exon 9 of F8 gene in homozygous state in the affected female born of 1° consanguinous marriage and in all the affected male members of the family. Her factor VIII levels was found to be 5.5%, vWF:Ag 120%.

CONCLUSION:

In India, as consanguineous marriages are very common in certain communities (up to 30%), the likelihood of encountering female hemophilia is higher, although this is the first case of HA out of 1600 hemophilia families registered in our Comprehensive Haemophilia Care Center. Genetic diagnosis in such cases is not necessary as all the male children will be affected and daughters obligatory carriers.     

Quadruplexes of human telomere DNA analogs designed to contain G:A:G:A,G:G:A:A,and A:A:A:A tetrads

Replacement of two to four guanines by adenines in the human telomere DNA repeat dG₃(TTAG₃)₃ did not hinder the formation of quadruplexes if the substitutions took place in the terminal tetrad bridged by the diagonal loop of the intramolecular antiparallel three‐tetrad scaffold, as proved by CD and PAGE in both Na⁺ and K⁺ solutions. Thermodynamic data showed that, in Na⁺ solution, the dG₃(TTAG₃)₃ quadruplex was destabilized, the least by the two G:A:G:A tetrads, the most by the G:G:A:A tetrad in which the adenosines replaced syn‐guanosines. In physiological K⁺ solution, the highest destabilization was caused by the 4A tetrad. In K⁺, only the unmodified dG₃(TTAG₃)₃ quadruplex rearranged into a K⁺‐dependent quadruplex form, none of the multiple adenine‐modified structures did so. This may imply biological consequences for nonrepaired A‐for‐G mutations. © 2010 Wiley Periodicals, Inc. Biopolymers 93: 880–886, 2010.     

Aminopeptidase A is angiotensinase A

Summary Quantitative histochemical measurements of aminopeptidase A (APA; E.C.3.4.11.7) were done kinetically in the kidney glomeruli of rat and mouse with an instrumental setup consisting of a microdensitometer and a computer-supported morphometric system. The histochemical demonstration of APA was carried out using the simultaneous azo coupling technique (purest-grade Fast Blue B as coupling agent and -l-glutamic acid-4-methoxy-2-naphthylamide as substrate). The methodological studies show that APA activity is calcium-ion-dependent and increases linearly with the thickness of the tissue section (3–12 m) and that the time-course of APA activity as determined by linear regression is linear only for the first 1 to 2 min of the reaction. — Kinetic measurements indicate a 40% decrease in APA activities when -l-glutamic acid-4-methoxy-2-naphthylamide (-l-Glu-MNA) is replaced by -l-aspartic acid-4-methoxy-2-naphthylamide. When -l-Glu-MNA is replaced with l-alanine-4-methoxy-2-naphthylamide, which is a substrate of aminopeptidase M (APM) only very low reaction rates are measurable (about 1.4% of those with -l-Glu-MNA). 100 and 130 mM NaCl in the incubation medium increase APA activities by approximately 16%–17%. — To clarify the functional importance of APA in the kidney, their activities were measured under the influence of angiotensins. The glomerulus was selected as the measuring site, for besides APA it contains no APM or other peptidases that could degrade angiotensins (the glomerular dipeptidyl peptidase IV is not inhibited by angiotensin II). Using the Lineweaver-Burk plot, we determined a K _m of 0.16 mM for the APA in rat glomeruli and 0.14 mM in mouse glomeruli. The V _max in mouse glomeruli is 1.6 times higher than in rat glomeruli. Ang iotensin I, II and III competitively inhibit APA in the rat and mouse glomeruli. — With quantitative histochemical techniques it was possible to show that APA is equivalent to angiotensinase A (splitting off the N-terminal aspartic acid from angiotensin I and II).Supported by the Deutsche Forschungsgemeinschaft (SFB 105)     

关于一个"基细胞"的疑问

有或没有基细胞是毛鞘藻属与枝鞘藻属的区别之一。这里叙述了Ｍｒｏｚｉｎｓｋａ在其专著中,将Ｏｅｄｏｃｌａｄｉｕｍ ｉｎｄｉｃｕｍ Ｋａｍａｔ附图（即模式图）上的一个基细胞错误地移置到Ｏｅ．ｐｒｅｓｃｏｔｔｉｉ Ｉｓｌａｍ上去的情况。     

关于一个“基细胞”的疑问

有或没有基细胞是毛鞘藻属(Bulbochaets)与枝鞘藻属(Oedocladium)的区别之一。这里叙述了Mrozinska在其专著(1985)中,将Oedocladium indicum Kama附图(即模式图)上的一个基细胞错误地移置到Oe.PrescottiiIslam上去的情况。     

A

A valley mire was sampled on the flanks of Swampy Hill, east Otago, New Zealand. It formed in a narrow valley, apparently originally comprising two basins. The end of the mire nearest the outlet contained species typical of fens (i.e., rheotrophic mires). At the head of the valley there was a section of the mire with mixed vegetation cover comprising the tussock grass Chionochloa rubra, Sphagnum species, and cushion/herb/shrub cover. Ombrotrophic status of this section was indicated by a slightly raised profile, greater acidity, lower exchangeable Na and K, and lower substrate cation exchange capacity, identifying it as a bog. Total Ca:Mg molar ratios were generally above 1.0, but this rule-of-thumb for ombrotrophic status may be inapplicable here. It is not known whether New Zealand Sphagnum species are as efficient at lowering the pH as those investigated elsewhere. Macrofosssil evidence indicates that some components of the bog, such as Sphagnum and epacridaceous subshrubs, have remained constant, almost since the inception of the bog. However, Empodisma minus, currently absent from the bog and rare in the region, was present at one stage. The change from cover with Empodisma and Dracophyllum as significant components, to the present Chionochloa/Sphagnum/cushion composition, occurred a few hundred years ago, probably initiated by fire. Comparison with preliminary information for other bogs suggests that those in the eastern part of the South Island vary considerably in species composition, with individualistic assemblages of species. The site is seen as having high conservation values. To protect these values the bog needs protection from invasive exotic weeds, and from damage by wild pigs.     

Role of CYP epoxygenases in A2A AR-mediated relaxation using A2A AR-null and wild-type mice

We hypothesized that A2A adenosine receptor (A2A AR) activation causes vasorelaxation through cytochrome P-450 (CYP) epoxygenases and endothelium-derived hyperpolarizing factors, whereas lack of A2A AR activation promotes vasoconstriction through Cyp4a in the mouse aorta. Adenosine 5'-N-ethylcarboxamide (NECA; 10(-6) M), an adenosine analog, caused relaxation in wild-type A2A AR (A2A AR+/+; +33.99 +/- 4.70%, P < 0.05) versus contraction in A2A AR knockout (A2A AR(-/-); -27.52 +/- 4.11%) mouse aortae. An A2A AR-specific antagonist (SCH-58261; 1 microM) changed the NECA (10(-6) M) relaxation response to contraction (-35.82 +/- 4.69%, P < 0.05) in A2A AR+/+ aortae, whereas no effect was noted in A2A AR(-/-) aortae. Significant contraction was seen in the absence of the endothelium in A2A AR+/+ (-2.58 +/- 2.25%) aortae compared with endothelium-intact aortae. An endothelial nitric oxide synthase inhibitor (N-nitro-L-arginine methyl ester; 100 microM) and a cyclooxygenase inhibitor (indomethacin; 10 microM) failed to block NECA-induced relaxation in A2A AR+/+ aortae. A selective inhibitor of CYP epoxygenases (methylsulfonyl-propargyloxyphenylhexanamide; 10 microM) changed NECA-mediated relaxation (-22.74 +/- 5.11% at 10(-6) M) and CGS-21680-mediated relaxation (-18.54 +/- 6.06% at 10(-6) M) to contraction in A2A AR+/+ aortae, whereas no response was noted in A2A AR(-/-) aortae. Furthermore, an epoxyeicosatrienoic acid (EET) antagonist [14,15-epoxyeicosa-5(Z)-enoic acid; 10 microM] was able to block NECA-induced relaxation in A2A AR+/+ aortae, whereas omega-hydroxylase inhibitors (10 microM dibromo-dodecenyl-methylsulfimide and 10 microM HET-0016) changed contraction into relaxation in A2A AR(-/-) aorta. Cyp2c29 protein was upregulated in A2A AR+/+ aortae, whereas Cyp4a was upregulated in A2A AR(-/-) aortae. Higher levels of dihydroxyeicosatrienoic acids (DHETs; 14,15-DHET, 11,12-DHET, and 8,9-DHET, P < 0.05) were found in A2A AR+/+ versus A2A AR(-/-) aortae. EET levels were not significantly different between A2A AR+/+ and A2A AR(-/-) aortae. It is concluded that CYP epoxygenases play an important role in A2A AR-mediated relaxation, and the deletion of the A2A AR leads to contraction through Cyp4a.     

Preparation of Radioactive Gibberellins A20, A5 and A8

Many yeasts were isolated from natural sources in the tropics and subtropics by enrichment culture technique, using medium which contained a surfactant. The medium was acidified with citric acid. A strain S–10 belonging to the genus Candida was found to produce itaconic acid. Under suitable conditions in shake culture, a mutant derived from this strain produced the acid at about 35 % yield on the basis of glucose supplied.     

Efficacy of antibiotics A204 sodium A28695A, and A204np against Coccidia of rabbits.

Three polycyclic, polyether, monocarboxylic acid antibiotics produced by and extracted from a strain of Streptomyces albus and designated A204 sodium, A28695A, or A204-np, were specifically tested for activity against hepatic and incidentally against intestinal coccidia of rabbits. All were effective in preventing infections and acceptable to young rabbits when prepared in pelleted feed. Weight gain, however, was not as good as inoculated, medicated rabbits as in noninoculated, nonmedicated controls. No gross pathologic changes were detected except in the livers of inoculated, nonmedicated controls which were severely infected on greatly enlarged. Livers of medicated rabbits were uninfected and normal in appearance and size.     

A Tribute to Thomas A. Sebeok

According to the approach developed by Thomas A. Sebeok (1921–2001) and his ‘global semiotics,’ semiosis and life converge. This leads to his cardinal axiom: ‘semiosis is the criterial attribute of life.’ His global approach to sign life presupposes his critique of anthropocentrism and glottocentrism. Global semiotics is open to zoosemiotics, indeed, even more broadly, biosemiotics which extends its gaze to semiosis in the whole living universe to include the realms of macro- and microorganisms. In Sebeok’s conception, the sign science is not only the study of communication in culture, but of communicative behaviour from a biosemiotic perspective.