Analysis of active sites for N2 and H^＋ reduction on FeMo-cofactor of nitrogenase

Dinitrogen (N2) and proton (H ),which act as physiological substrates of nitrogenase,are reduced on FeMo-co of the MoFe protein. However,researchers have different opinions about their exact reduction sites. Nitrogenases were purified from the wild type (WT) and five mutants of Azotobacter vinelandii (Av),including Qα191K,Hα195Q,nifV-,Qα191K/nifV- and Hα195Q/nifV-; and the activities of these en-zymes for N2 and H reduction were analyzed. Our results suggest that the Fe2 and Fe6,atoms closed to the central sulfur atom (S2B) within FeMo-co,are sites for N2 binding and reduction and the Mo atom of FeMo-co is the site for H reduction. Combining these data with further bioinformatical analysis,we propose that two parallel electron channels may exist between the 8Fe7S cluster and FeMo-co.     

较为精密的Hardy-Hilbert不等式的一个加强

对 Hardy-Hilbert 不等式进行了研究,并将其进一步改进如下:若1,11 p p q>+=,,01 a b ≥,使n n 11 q<∞∑∞∑∞则∑∑∞∞a b m n????p????0   

化学模拟生物固氮——Ⅶ.乙炔选择性还原成乙烯作为原子簇活性中心多核络合活化底物的一种判据

系统地比较了FeMo-co和固氮酶的各种模拟体系在KBH_4还原乙炔为乙烯的反应中的催化活性和选择性。FeMo-co(活性:转变数为34;选择性:99％C_2H_4)和本实验室合成的模型化合物(活性:转变数为20～30;选择性;91～95％)比其它固氮酶的模拟体系(MoO_4~(2-)-CySH;MoO_4~(2-)—CySH—Fe~(2 );MoOS_4~(2-)—胰岛素;[Fe_4S_4(SCH_2Φ)_4]~(2-);和MoS_4~(2-))具有较高的活性和选择性;这可作为FeMo—co及其合成模拟物的原子簇活性中心多核络合活化底物分子的一种判据.     

固氮酶催化作用机理及其化学模拟

固氮酶是某些微生物在常温常压下固氮成氨的主要催化剂,其催化机理和化学模拟是国际上长期致力研究的对象。尽管人们已经揭示了固氮酶催化活性中心——铁钼辅基（FeMo-co)MoFe7S9（R-高柠檬酸）的结构,然铡,有关FeMo-co生物合成的详细途径和其中包含的钼铁转移和利用;固氮酶在哪些活性位和按什么模式结合N2,C2H2、CO等多种底物或抑制剂;以及其中涉及的电子和质子传递过程等许多问题,至今尚有待解决。本文将综述这些问题的研究进展和厦门大学固氮组最近五年来的相关研究工作。     

《少儿科技》要改版了!——2008年改为月刊

您是不是觉得每一期杂志需要两个月的等待时间实在是太漫长了呢?您是不是觉得我们现有的容量还不能满足您如饥似渴的求知欲望呢???不用担心,2008年您的愿望都将会得到满足。     

固氮酶铁钼辅因子模型化合物合成的研究——Ⅰ、光谱法研究合成方法的设计方案

本文讨论了以K_2MoS_4,FeCl_2,KOR(R=-CH_2CH_2OH或-CH_3)为基本原料,合成固氮酶铁钼辅因子(FeMo-co)模型物合成方案的设计依据。系统地考察这种体系的电子吸收光谱和激光拉曼光谱特征及其随时间的变化。实验结果支持了所提出合成方案的设计依据。     

预测新的生物胺受体配基结合位点

生物胺受体被认为是一类重要的药物靶标,用生物信息学手段寻找它的配基结合位点并分析其功能,对于药物设计具有重要的指导意义.从整体上结合可变性、疏水性和保守性构建了受体的2D螺旋横切面模型,预测出其可能的配基结合区Ⅰ、Ⅱ,其中TM3、TM4以及TM7在配基结合中起关键作用,E-Ⅱ环也参与了配基结合这一过程,这是对以往普遍认为只有TM参与配基结合的延伸.从局部上寻找了生物胺受体及其子受体的基序,提出了家族可变亚家族保守基序(motif)概念,即家族可变区中找到的亚家族保守的基序.最后结合整体与局部分析结果分析了各基序的功能,预测了行使配基结合功能的基序及其相应位点,结果证明与突变实验结果有很好的吻合度.     

染料配基层析介质的合成及其纯化功能的研究

采用合成的１２个染料配基及催化偶联方法制成亲和层析介质，比较了不同结构的配基对碱性磷酸酶的选择纯化功能。配基中模仿天然辅酶杂环结构的三嗉环及两端的带电荷基团具有重要的功能作用。     

抗体亲和肽配基的高通量筛选和理性设计

抗体是一类能与抗原特异性结合的免疫球蛋白,在疾病治疗和检测方面应用前景广阔.目前抗体的分离纯化是其生产的瓶颈.高选择性的亲和色谱技术在抗体纯化过程中发挥着越来越重要的作用,而配基的高通量筛选和设计是亲和色谱技术应用的关键因素.短肽是一种常见的亲和配基类型.本文根据近年来国内外抗体亲和肽配基的研究情况,综述了抗体亲和肽配基的高通量筛选和理性设计方法,重点介绍其作用机理、发展现状以及目前存在的主要问题.最后展望了短肽配基仿生设计技术.     

全氟化的钾外掺杂富勒烯 K???C24F24的结构与额外电子特性研究

采用 B3LYP/6-311+G(d)方法研究了钾外掺杂的全氟化富勒烯 K???C24F24体系的结构及额外电子特性.计算结果显示,在 K 和 C24F24笼的强相互极化作用下,K 的价电子转移到 C24F24笼中形成额外电子和键长大于3.0?的新型长程 K+???C24F24-弱离子键(相互作用能为-65.63 kcal/mol).由于额外电子作负离子,K???C24F24体系具有明显的 electride 特征.值得注意的是,额外电子的一部分占据于笼子内部而另一部分占据在笼子骨架上.这使得其具有独特的部分溶剂化电子和部分偶极束缚电子的特征.我们还计算了 K+???C24F24-的额外电子吸收光谱     

FeMo－co模拟物体系的性能表征

根据蛋白键合ＦｅＭｏ－ｃｏ的Ｋ－Ｒ模型，合成了两个ＦｅＭｏ－ｃｏ模拟物的体系，这两个体系的可见光谱和Ｍｏ／Ｆｅ／Ｓ组成都接近于天然分离的ＦｅＭｏ－ｃｏ．模拟物体系经柠檬酸盐缓冲液稀释后，再与ＵＷ４５的组份１组合，都表现出高乙炔还原活性．     

新型内含肽介导PHB系统表达纯化PoIFN-α的研究

为简化猪α干扰素蛋白（PoIFNα）的纯化步骤,以蛋白质自切割元件内含肽（Intein）替代蛋白酶,并以细菌自身产生的聚β-羟基丁酸酯（PHB）颗粒替代亲和配基,构建了新型内含肽介导PHB纯化PoIFNα的体系.结果显示,构建的基因工程大肠杆菌系统可成功实现PoIFNα的表达和纯化;φ（乳酸钠）=2.7%时,比较适宜工程菌的PHB累积;当诱导自切割反应温度为20℃,pH=6.5,反应时间为24~36 h时,可以实现内含肽C端高效自切割,纯化出的PoIFNα产量为20~30 mg/L.实验为重组猪α干扰素的工业化规模生产奠定了基础.     

无孔单分散亲水性硼酸基亲合色谱固定相的制备及其在几种抗生素分离中的应用

以自制3.0μm无孔单分散亲水性交联聚甲基丙烯酸环氧丙酯树脂P(GMA/EDMA)为载体,间氨基苯硼酸为配体制备了一种新型高效硼酸基亲合色谱填料.考察了抗生素:去甲万古霉素、阿米卡星、异帕米星和庆大霉素,与硼酸配体的特异性作用,以及流动相中盐离子浓度和pH对抗生素保留的影响.结果表明:表面带有邻羟基的抗生素和硼酸基具有特异性亲合作用,且抗体结构中具有不同的邻羟基数目表现出不同的保留能力.用所合成的硼酸基亲合色谱柱纯化去甲万古霉素,结合反相色谱检测其纯化液,证明所制备的硼酸基亲和色谱柱具备纯化去甲万古霉的能力.     

Ghrelin is a growth-hormone-releasing acylated peptide from stomach

Small synthetic molecules called growth-hormone secretagogues (GHSs) stimulate the release of growth hormone (GH) from the pituitary. They act through GHS-R, a G-protein-coupled receptor for which the ligand is unknown. Recent cloning of GHS-R strongly suggests that an endogenous ligand for the receptor does exist and that there is a mechanism for regulating GH release that is distinct from its regulation by hypothalamic growth-hormone-releasing hormone (GHRH). We now report the purification and identification in rat stomach of an endogenous ligand specific for GHS-R. The purified ligand is a peptide of 28 amino acids, in which the serine 3 residue is n-octanoylated. The acylated peptide specifically releases GH both in vivo and in vitro, and O-n-octanoylation at serine 3 is essential for the activity. We designate the GH-releasing peptide 'ghrelin' (ghre is the Proto-Indo-European root of the word 'grow'). Human ghrelin is homologous to rat ghrelin apart from two amino acids. The occurrence of ghrelin in both rat and human indicates that GH release from the pituitary may be regulated not only by hypothalamic GHRH, but also by ghrelin.     

2,3-二氯苯基哌嗪合成方法的改进

2,3-二氯苯胺硫酸盐经重氮化,再与KI置换生成相应的芳基碘化物,产率81%.芳基碘化物与哌嗪在二甲基亚砜中反应,CuI和脯氨酸为催化剂,收率20%.该方法操作简单,对湿不敏感，产物易于分离，具有一定的实用价值。     

Identification of the V factor needed for synthesis of the iron-molybdenum cofactor of nitrogenase as homocitrate

Nitrogenase catalyses the ATP-dependent reduction of N2 to NH3, and is composed of two proteins, dinitrogenase (MoFe protein or component I) and dinitrogenase reductase (Fe protein or component II). Dinitrogenase contains a unique prosthetic group (iron-molybdenum cofactor, FeMoco) comprised of Fe, Mo and S, which has been proposed as the site of N2 reduction. Biochemical and genetic studies of Nif- (nitrogen fixation) mutants of Klebsiella pneumoniae which are defective in nitrogen fixation, have shown that the nifB, nifQ, nifN, nifE and nifV genes are required for the biosynthesis of FeMo-co. Recently, a system for in vitro synthesis of FeMoco was described. The assay requires at least the nifB, nifN and nifE gene products, and a low-molecular-weight factor (V factor) produced in the presence of the nifV gene product. We have used this system to study FeMoco biosynthesis. We report here the isolation of V factor and identify it as homocitric acid ([R]2-hydroxy-1,2,4-butanetricarboxylic acid).     

CD43, a molecule defective in Wiskott-Aldrich syndrome, binds ICAM-1.

THE protein CD43 (also known as sialophorin, leukosialin, large sialoglycoprotein or gp115) is expressed on the surface of T lymphocytes, monocytes, neutrophils, platelets and some B lymphocytes. Expression of CD43 is deficient and/or defective in the X-chromosome-linked immunodeficiency disorder Wiscott-Aldrich syndrome, suggesting that CD43 might have a role in T-cell activation. We have shown that expression of human CD43 in an HLA-DR-specific murine T-cell hybridoma enhances the antigen-specific response to stimulation by the human lymphoblastoid cell line Daudi, and that Daudi cells bind specifically to purified immobilized CD43. These data indicate that the specific interaction of CD43 with a ligand on the surface of Daudi cells might contribute to T-cell activation. Here we report evidence that intercellular adhesion molecule-1 (ICAM-1, or CD54), is a ligand for CD43.     

转CaM基因工程菌的培养及重组钙调素的提纯

研究了转植物ＣａＭ基因的大肠杆菌的培养以及从该工程菌中分离纯化ＣａＭ的方法,观察到在含氨苄青霉素及氯菌素的ＬＢ液体培养其中,