反向DPPC脂囊泡中短杆菌肽S的二维氢核磁共振研究

本文用300MHz核磁共振仪对反向DPPC脂囊泡中短杆菌肽S进行了研究.用二维相关谱(COSY)和二维NOE谱(NOESY)对反向脂囊泡中短杆菌肽S的共振峰进行了识别,短杆菌肽S所有的共振峰都被指定.并在此基础上,通过NOESY及一维自旋回波谱对短杆菌肽S在反向脂囊泡中的构象进行了分析.结果表明,短杆菌肽S在反向脂囊泡中不再为平面环状结构,而是有某种程度的折叠.     

同脂膜结合的短杆菌肽S的扫描隧道显微镜观察

将短杆菌肽Ｓ与二棕榈酰磷脂酰胆碱脂质体复合物滴于高定向裂解石墨,充分干燥后,用扫描隧道显微镜进行观察,可以得到：１．磷脂分子在石墨表面有规则的二维排列的图像;２．短杆菌肽Ｓ在石墨表面自组合形成的二维晶体的图像和３．短杆菌肽Ｓ平躺于磷脂分子头部的图像。根据短杆菌肽Ｓ在石墨上排列的二维晶格常数和分子大小可知,在石墨表面,短杆菌肽Ｓ以二聚体形式存在。这同短杆菌肽Ｓ的晶体衍射结果一致。但从短杆菌肽Ｓ平躺于磷脂头部的图像上可以分辨出：在脂环境中,短杆菌肽Ｓ以单体形式存在。最后,根据短杆菌肽Ｓ分子的大小与磷脂分子在石墨表面排列的二维晶格常数,得出了短杆菌肽Ｓ同二棕榈酰磷脂酰胆碱分子的作用模式图     

吩噻嗪类钙调素抑制剂对芽殖酵母(Saccharomyces cerevisiae)和粟酒裂殖酵母(Schizosaccharomyces pombe)细胞增殖的不同效应

低浓度的TFP、CPZ及FPZ能明显促进S．Pombe细胞的增殖,培养液中Ca2+浓度越低,TFP等的促进作用越显著,Ca2+与TFP具有协同促进S.pombe增殖的功能;但20μmol／LTFP能终止S．Cerevisiae细胞周期的运转。TFP的细胞膜通透性研究表明,20μmol／LTFP就能进入到S.cerevisiae细胞中,但不易穿过S．Pombe细胞膜却能明显促进Ca2+的内流,引起S.pombe胞内Ca2+总量的迅速增加。因此认为低度的TFP促进S.pombe细胞的增殖,不是因为TFP进入到胞内作为CaM的抑制剂而起的作用,而是通过促进胞外钙的内流从而促进S．Pombe细胞的增殖。     

细胞的荧光标记与融合检测细胞膜的流动性

细胞膜是细胞的物理屏障,也是在细胞生命活动中有复杂功能的重要结构.细胞膜把细胞包裹起来,使细胞能够保持相对的稳定性,维持正常的生命活动,保证必需养分的吸收和代谢产物的排出等.细胞膜结构具有共同特征:镶嵌性,蛋白质极性及流动性等.笔者使用同种细胞作为实验材料,用同种膜蛋白的抗体进行免疫,然后用带有不同荧光的二抗标记,最后对细胞进行融合,实验结果证明细胞膜是具有流动性的.     

细胞膜的制备与观察

细胞膜是细胞表面的一层薄膜.细胞膜由磷脂双层和相关蛋白质以及胆固醇和糖脂组成,其化学组成主要是脂类、蛋白质和糖类.细胞膜有重要的生理功能,它既是细胞维持稳定代谢的胞内环境,又能调节和选择物质进出细胞,又负责细胞间的信息交流.通过微分干涉差显微镜和普通光学显微镜观察人红细胞制备的细胞膜,效果明显.     

细胞-场效应管传感器及其应用

细胞膜电位是由细胞膜内外两侧离子浓度差所产生的电位差,包含静息电位和动作电位.电压钳和膜片钳是细胞膜电位检测和记录的主要技术,电压钳的电极和膜片钳的玻璃管对细胞膜有刺激,并且不能对细胞进行在线监测和记录.细胞-场效应管传感器是一种用细胞膜电位通过场效应管栅极控制漏源电流,从而感受细胞膜电位的新型器件,具有对细胞膜无刺激、在线、长时程、实时等特点,是细胞膜电位检测和记录的新技术,可广泛应用于科学研究、药物开发、医疗器械、检验检疫、环境保护、公共安全等领域.本文主要介绍这种传感器的结构、转移特性、等效电路、制备工艺以及动作电位记录、细胞生长实时监测、细胞外分泌监测、肿瘤标志物检测等方面的应用.     

天花粉蛋白引起敏感细胞膜上G蛋白激活的初步研究

天花粉蛋白(Trichosanthin,TCS)是一种单链核糖体失活蛋白,具引产、抗肿瘤、抗HIV等多种生物学功能。天花粉蛋白专一性杀伤敏感细胞的机制一直未被研究清楚。本文首次以生物分子相互作用分析(BIA)证明在天花粉蛋白敏感的细胞膜上存在着能与天花粉蛋白专一结合的组分。我们进一步利用[~(35)S]GTPγS结合实验发现天花粉蛋白能够激活敏感细胞膜上的G蛋白,而对不敏感细胞没有相应的G蛋白激活。这些结果表明了在敏感细胞膜上天花粉蛋白特异受体的存在。     

转录组分析揭示玉米大斑病菌对解淀粉芽孢杆菌胁迫响应机制

在植物病害生物防治系统中,生防微生物的生物防治机制是关注的重点,而植物病原物如何响应并抵抗或缓解生防微生物胁迫的机制往往被忽略.本文以解淀粉芽孢杆菌(Bacillus amyloliquefaciens)和玉米大斑病菌(Setosphaeria turcica)为生防互作系统,利用RNA-seq技术研究S.turcica对B.amyloliquefaciens生防胁迫响应的分子机制,结果表明,与对照S.turcica样品比较,B.amyloliquefaciens发酵液处理的S.turcica样品中共有393个基因显著差异表达,其中168个基因上调表达,225个基因下调表达.已知解淀粉芽孢杆菌的抗菌物质一般作用于真菌细胞壁、细胞膜,通过破坏细胞壁及细胞膜的结构抑制真菌生长,因此,本研究在差异表达基因中重点分析S.turcica细胞壁、细胞膜结构相关基因,发现S.turcica上调表达细胞壁组分蛋白(1-6)-beta-D葡聚糖生物合成途径基因、麦角固醇合成途径Delta(14)甾醇还原酶基因、脂肪酸合成酶基因、抗氧化相关的抗坏血酸过氧化物酶基因、谷胱甘肽硫转移酶基因、腺苷三磷酸结合盒转运蛋白基因;下调表达调控细胞凋亡的Metacaspase基因.这说明S.turcica通过调节芽孢杆菌抗菌活性物质的靶标蛋白或合成途径的基因表达,以缓解B.amyloliquefaciens的生防胁迫作用,是一种涉及多个基因和多个信号途径共同参与调控的复杂网络.该研究结果将为研究病原真菌对生防微生物胁迫的抗性机制奠定基础.     

小鼠肝炎病毒S蛋白及其受体的研究现状

MHV表面S蛋白介导多种重要的生物学功能,包括对易感细胞受体的吸附、侵入阶段病毒与细胞膜的融合、病毒传播过程中细胞与细胞的融合,以及免疫激活、组织嗜性、病毒致病性的变异。S蛋白对受体mCEACAM的识别是MHV感染种属特异性和组织趋向性的最初决定因素,不同MHV毒株S1亚基的长度及核苷酸序列都呈现高度多态性,这些突变导致抗体表位和T细胞表位缺失,为病毒逃避免疫监视提供一条途径。     

多不饱和脂肪酸对细胞膜功能影响的研究进展

多不饱和脂肪酸是细胞膜磷脂的重要组成成份,影响细胞膜的稳定性.它具有广泛的生物学功能,包括细胞内信号传导通路、基因表达和细胞凋亡的调控等.主要从细胞膜脂质的组成,细胞膜的流动性及膜脂质过氧化等方面对多不饱和脂肪酸对细胞膜功能的影响进行了综述.     

Conformation of gramicidin S

A molecular conformation of Gramicidin S was derived on the basis of conformational calculations taking into account the available experimental data. The conformation is characterized by a dyad axis which relates the two chemically equivalent halves of the molecule and contains four hydrogen bonds; other structural features agree with experimental results. X Ray Crystallographic evidences for the relative position of the Ornithine residues is also reported which supports an important feature of the structure of Gramicidin S.     

The influence of gramicidin S on hydrophobicity of germinating Bacillus brevis spores

Gramicidin S is known to prolong the outgrowth stage of spore germination in the producing culture. Bacillus brevis strain Nagano and its gramicidin S-negative mutant, BI-7, were compared with respect to cell-surface hydrophobicity and germination of their spores. Parental spores were hydrophobic as determined by adhesion to hexadecane, whereas mutant spores showed no affinity to hexadecane. Addition of gramicidin S to mutant spores resulted in a high cell surface hydrophobicity and a delay in germination outgrowth. The hydrophobicity of parental spores was retained throughout most of the germination period. Hydrophobicity was lost as outgrowing spores entered into the stage of vegetative growth. The data indicate that gramicidin S is responsible for the hydrophobicity of B. brevis spores. It is suggested that in making spores hydrophobic, the antibiotic plays a role in concentrating the spores at interfaces where there is a higher probability of finding nutrients for germination and growth.Abbreviation GS Gramicidin S     

Water structure in the Gramicidin A transmembrane channel

The interaction energy and the structure of water molecules either inside the Gramicidin A transmembrane channel or at its two extremities is examined with the use of iso-energy maps and Monte Carlo simulations. The shape of the channel as experienced by water is analyzed in detail. Variations in the hydration structure due to the presence of a sodium ion placed at several positions along the channel are simulated, analyzed and discussed. Preliminary data on Li+ and K+ interacting with Gramicidin A and the system of water molecules are reported. The Gramicidin A atomic coordinates have been taken from Urry's recent papers (Urry, D.W. (1971) Proc. Natl. Acad. Sci. U.S.A. 68, 672-676 and Urry, D.W., Trapane, T.L. and Prasad, K.U. (1982) Int. J. Quant. Chem. Quant. Biol. Symp. 9, 31-40).     

Inhibition of fungal spore germination by gramicidin S and its potential use as a biocontrol against fungal plant pathogens

Gramicidin S, as well as being sporicidal to Bacillus spores, also inhibits germination and emergence of fungal-like spores of Dictyostelium discoideum . The fungal plant pathogen Fusarium nivale is also inhibited and gramicidin S, therefore, is a sporicidal and antifungal antibiotic. Considering these findings the potential use of this antibiotic and its producer organism Bacillus brevis as a biocontrol is discussed.     

Studies on lysine:N6-hydroxylation by cell-free systems of Aerobacter aerogenes 62-1

Electron microscopic examination has revealed the vesicular nature of the membrane component, of the cell-free system of Aerobacter aerogenes 62-1, which catalyses lysine: N6-hydroxylation. Regardless of the orientation of the vesicles, N-hydroxylation process is still stimulated by pyruvate. Both pyruvate oxidation and lysine: N6-hydroxylation were inhibited by protonophores and Gramicidin S.     

Effect of inductors of alkali cation permeability on cytochrome c bound to mitochondrial membrane]

The effect of inductors of alkali cation permeability--valinomycin, gramicidin A, gramicidin S and its N,N'-diacetyl derivative--on rat liver mitochondria during respiration has been studied. It is shown that valinomycin, gramycidin A and diacetylgramicidin S at optimal concentration for uncoupling cause two-phase activation of mitochondrial respiration and that this effect results from cytochrome c solubilization. Gramicidin S at optimal concentration cannot remove cytochrome c from the respirating mitochondria. It is suggested that this property of gramicidin S is owned to cytochrome c immobilisation in membrane, due to the effect of this compound.     

Infrared spectra of the Gramicidin A transmembrane channel: the single-stranded-beta 6-helix

IR spectra are reported for preparations of Gramicidin A and malonyl Gramicidin A incorporated as the channel state in phospholipid structures. In this preparation Gramicidin A has already been shown to be unequivocally in the single-stranded beta-helical conformation. The result is an amide I frequency of 1633 +/- 1 cm-1. This demonstrates that the single-stranded beta-helix has an amide I frequency that has previously been considered to be diagnostic of antiparallel double-stranded beta-helix and of beta-sheet structures.     

Gramicidin S inhibition of the Ca2+-ATPase of human red blood cells

The cationic amphiphilic polypeptide gramicidin S inhibits the Ca2+-ATPase of human red-cell membranes by lowering the maximum velocity of the high-affinity component and the apparent affinity of the low-affinity component of the velocity-versus-ATP concentration curve of the enzyme. Gramicidin S does not alter the apparent affinity of the Ca2+-ATPase for Ca2+. Calmodulin is not essential for the inhibition, but increases the sensitivity of the enzyme to the inhibitor. The effects of gramicidin S on the Ca2+-ATPase can be reversed with phosphatidylcholine vesicles but not with buffer solutions, suggesting that gramicidin S acts from the lipid phase of the membrane.     

Water structure in the Gramicidin A transmembrane channel

The interaction energy and the structure of water molecules either inside the Gramicidin A transmembrane channel or at its two extremities is examined with the use of iso-energy maps and Monte Carlo simulations. The shape of the channel as experienced by water is analyzed in detail. Variations in the hydration structure due to the presence of a Na+ ion placed at several positions along the channel are simulated, analyzed and discussed. Preliminary data on Li+ and K+ interacting with Gramicidin A and the system of water molecules are reported. The Gramicidin A atomic coordinates have been taken from Urry's recent papers.     

Water Structure in the Gramicidin A Transmembrane Channel

Abstract

The interaction energy and the structure of water molecules either inside the Gramicidin A transmembrane channel or at its two extremities is examined with the use of iso-energy maps and Monte Carlo simulations. The shape of the channel as experienced by water is analyzed in detail. Variations in the hydration structure due to the presence of a Na+ ion placed at several positions along the channel are simulated, analyzed and discussed. Preliminary data on Li+ and K+ interacting with Gramicidin A and the system of water molecules are reported. The Gramicidin A atomic coordinates have been taken from Urry's recent papers.