毒素蛋白Colicin E1与磷脂膜相互作用的荧光光谱研究——临界摩尔…

磷脂－蛋白相互作用的临界摩尔比是研究膜脂－蛋白相互作用的重要参数。本文利用荧光光谱技术首次测定了毒素蛋白Ｃｏｌｉｃｉｎ Ｅ１在不同条件下与不同磷脂膜相互作用的临界摩尔比并通过临界摩尔比的变化讨论了插膜蛋白与磷脂膜相互作用的规律，为进一步探讨毒素蛋白的插膜机制提供了重要的基础。     

F-肌动蛋白与负电荷磷脂膜的相互作用研究

细胞膜的内膜含有大量的负电荷磷脂,研究F-肌动蛋白与负电荷磷脂的相互作用将有助于更深入地了解细胞骨架与细胞膜的体内相互作用机制.在金片和金电极上分别构建了负电荷磷脂的杂化双层磷脂膜,通过表面等离子体共振方法(SPR)和电化学阻抗技术研究了F-肌动蛋白与负电荷磷脂膜的相互作用.结果表明,F-肌动蛋白可以在没有中间联系蛋白的情况下,直接与负电荷磷脂膜发生相互作用.钙离子可以有效地促进它们的相互作用,表明钙离子在其中发挥了重要作用.高浓度的KCl显著抑制它们的相互作用,表明这种相互作用主要受静电作用影响.实验结果进一步证明在F-肌动蛋白与负电荷磷脂膜相互作用时,除了可以通过其它蛋白发生间接相互作用外,还可以与磷脂膜发生直接的相互作用.     

用液相二次离子质谱技术探测Melittin与磷脂膜的相互作用

利用液相二次离子质谱技术(LSIMS)结合特异性蛋白酶降解研究了膜结合Melittin的“抛锚”状态.结果显示,Melittin(蜂毒素)分子在磷脂膜上为平躺α-螺旋结构,其螺旋中含Lys_7,Lys_(21),Arg_(22)的一侧朝向磷脂膜的外部.这一发现对蜂毒素插膜机制的研究具有十分重要的意义.结果还表明,质谱技术与专一性蛋白水解酶的结合为膜插入机制的研究提供了一个崭新的、行之有效的方法.     

制菌霉素与固体支撑磷脂膜的相互作用

为了更好地了解制菌霉素的作用机理, 本文利用表面等离子体共振(SPR)和交流阻抗两种技术, 考察了制菌霉素与不含固醇的固体支撑纯磷脂膜的相互作用, 结果发现, 制菌霉素可与纯磷脂膜相互作用, 并可能在膜上形成微孔.     

磷脂膜色谱及其在药物跨膜转运评价中的应用

磷脂膜色谱是固态基质上的有序磷脂分子单层体系采用色谱学方法仿真药物与细胞膜相互作用过程,可用来评价药物的细胞膜渗透性和活性。硅胶表面上的磷脂单分子层模拟了单层细胞膜,因此药物的磷脂膜色谱保留行为可用于预测药物与细胞膜的相互作用。目前考察药物跨膜转运的模型主要有正辛醇/水系统、脂质体/水系统、反相色谱（ODS）以及磷脂膜色谱。与前述3种系统比较,磷脂膜色谱除了具有高效、简便等特点外,同时能模拟药物与生物膜之间疏水作用力以外的其他作用力,因此对磷脂膜色谱的研究也越来越深入。由于药物细胞膜渗透性对其有效性和安全性起着关键作用,因此磷脂膜色谱在新药研发早期阶段的介入可以有效地降低后期候选药物的淘汰率,提高新药的研发效率。该文就磷脂膜色谱的研究及在药物跨膜转运评价中的应用进行了综述。     

磷脂膜的相行为对氧化石墨烯与磷脂膜相互作用的影响

通过使用不同相变温度的磷脂分子并调节二者的比例构筑了不同相态的磷脂膜, 并利用表面增强红外光谱和激光共聚焦显微镜研究了磷脂膜的相行为对氧化石墨烯和磷脂膜相互作用的影响. 结果表明, 氧化石墨烯对磷脂膜中磷脂分子的抽提作用具有显著的相态选择性, 其选择性地抽提流动相的磷脂分子; 氧化石墨烯对流动相磷脂的抽提作用受到膜中凝胶相磷脂存在比例的影响, 只有在流动相磷脂分子占磷脂膜中磷脂分子的绝大部分时才能够发生抽提作用, 且只有流动相的磷脂分子被抽提.     

pH对磷脂膜中Slc11a1跨膜区二级结构和取向的影响

采用圆二色光谱、 荧光光谱、 红外衰减全反射光谱和差示扫描量热分析等方法对不同pH条件下膜蛋白Slc11a1(溶质转运蛋白家族11成员1)的第二、 第三和第四跨膜区(TMD2~TMD4)在磷脂膜[二肉豆蔻酰磷脂酰胆碱(DMPC)和二肉豆蔻酰磷脂酰甘油(DMPG)的摩尔比为2∶1]中的二级结构和取向进行了研究. 结果表明, TMD3的二级结构及在磷脂膜内的位置与pH密切相关, 在pH=7时TMD3主要为β股结构, 在膜中埋入较浅; 而在pH=5.5时TMD3形成部分α螺旋结构, 并较深地埋入膜中. 对TMD3进行E139A突变后的结果证明, TMD3的这些性质与位于中间的谷氨酸的质子化性质密切相关. 实验结果还表明, TMD2和TMD4在不同pH条件下都形成α螺旋结构并分别以26°和35°的倾斜角插入磷脂膜内, 它们在磷脂膜内的位置基本不受pH影响.     

表面修饰富勒烯的聚酰胺-胺树枝状分子与生物膜的相互作用研究

采用粗粒化的分子动力学模拟,研究了末端修饰富勒烯(C60)的聚酰胺-胺(PAMAM)树枝状分子在水溶液中的结构变化以及其与磷脂膜相互作用行为.发现修饰后的PAMAM分子大小随嫁接数目的增多而减小,而形状变化并不明显,分子仍是近球形结构;同时发现C60分子因疏水作用聚集在一起.与膜作用后,因C60分子插入到双层膜内,导致分子由球形稍微向椭球形改变,分子大小也稍微增大.同时发现PAMAM分子紧紧分布在磷脂膜表面,局域膜厚度变小.     

锆镁磷脂膜色谱固定相的制备及其在评价药物-膜相互作用中的应用

基于锆基质与磷脂之间强烈的路易斯酸碱作用,制备了锆镁磷脂膜色谱固定相,并使用红外光谱、X射线光电子能谱对该色谱固定相进行了表征;使用与体内环境类似的生理缓冲液体系为流动相,评价了该模拟生物膜色谱固定相预测药物膜渗透性的能力,结果表明药物在锆镁磷脂膜色谱中的保留(log Kmbm)与表观渗透率(log Papp)在预测药物的膜渗透性、跨膜吸收等方面具有非常好的相关性,相关系数为0.970,斜率接近1。通过理论推导,引入了直观、方便的热力学指标吉布斯自由能差值（Δ(ΔG°)）对药物-膜之间的相互作用强弱进行了评价。     

平板双分子层脂膜的制备及锌离子跨该膜的输运过程

制备了氧化胆固醇 卵磷脂(脑磷脂)平板双分子层脂膜,研究了膜配方对双分子层脂膜的稳定性和离子通透性的影响,得到了最佳制膜工艺,建立了锌离子跨卵 (脑 )磷脂膜的吸附 -扩散模型,其计算值与实验值基本吻合.     

季铵盐型双子表面活性剂与十八醇的混合单分子膜

研究了双子表面活性剂12-2-16和12-2-12分别与十八醇(C18H37OH)在空气-水界面上混合单分子膜的π-A等温线. 在相分离表面压以下, 比较了不同表面压下和不同混合比单分子膜的混合表面过剩自由能ΔGMexo, 分析了双子表面活性剂与脂肪醇在空气-水界面上混合膜中的相容性. 结果表明, 12-2-16与C18H37OH在所有混合摩尔比下随着表面压增高, 自由能增大. 12-2-12与C18H37OH混合膜体系的相容性取决于两者的混合比, ΔGMexo随所加入C18H37OH摩尔分数的增加逐渐增大, 从异种分子间净的吸引作用转变到相互排斥作用体系, 转变点为C18H37OH加入量的摩尔分数0.65. 当混合为热力学自发过程时, 增大表面压将有利于混合; 而对相互排斥体系, 增加表面压将使体系内异种分子之间的相互排斥作用更大.     

A mechanistic study of the permeation kinetics through biomembrane models: gemcitabine-phospholipid bilayer interaction

The kinetics of the interaction between Gemcitabine (a new anticancer drug) and phospholipid membrane models was investigated. This kind of study is of particular importance both in hypothesizing the interaction of Gemcitabine with mammalian cell membranes and in evaluating the potentiality of liposomes as a Gemcitabine delivery system. Unilamellar (LUV) and multilamellar (MLV) membrane models were made up of dimyristoylphosphatidylcholine (DMPC), dimyristoylphosphatidic acid sodium salt (DMPA), or a DMPC-DMPA mixture (1:1 molar ratio). Gemcitabine-phospholipid vesicle interaction was studied by differential scanning calorimetry (DSC) measurements performed at different time intervals. The findings showed slower permeation kinetics of Gemcitabine through MLV than LUV which, at the same lipid/water ratio, are characterized by a larger lipid surface in contact with the drug aqueous solution. Another interesting difference between LUV and MLV is the onset of a transient two-peak structure during the DSC scans of MLVs. The effect is due to the unequal distribution of the drug between the outer and inner bilayers of the multilamellar vesicles during the permeation kinetics. At equilibrium the two-peak structure merges into a unique peak. This finding may provide useful information about the lipid bilayer permeability in model membranes.     

Synergistic effect and hierarchical nanostructure formation in mixing two designer lipid-like peptide surfactants Ac-A6D-OH and Ac-A6K-NH2

We here report the nanostructures from combinational self-assembly of two designer lipid-like peptides Ac-A6D-OH and Ac-A6K-NH2 using dynamic light scattering (DLS) and atomic force microscopy (AFM). The synergistic phenomenon is observed by measuring the critical aggregation concentrations (CACs) of these two mixed peptides, in different molar ratios by DLS. The nanoropes were observed in AFM images at a molar ratio of Ac-A6D-OH/Ac-A6K-NH2 = 1:1, and the thin film formation with aligned nanoropes is shown at a molar ratio of 2:1. The well aligned nanoropes at the molar ratio of Ac-A6D-OH/Ac-A6K-NH2 = 2:1 indicated the competition factor between the electrostatic repulsion according to DLVO theory and the hydrophobic interaction arising from the long side chains on lysine residues. This study will further our understanding for designing new nanomaterials based on designer lipid-like peptide surfactants.     

锌试剂与壳聚糖的结合反应机理的研究

为从分子水平认识多糖分子与小分子之间相互作用的机理,应用光谱法研究了壳聚糖(CTS)与锌试剂(ZCN)的相互作用机理;测得ZCN-CTS复合物吸收光谱出现新的吸收峰所需的临界ZCN/CTS摩尔比为2.67×103, CTS对ZCN的最大结合数为6.93×103,实验值与理论值相吻合,证明了多糖与生物探针相互作用理论模型的可靠性;探讨了ZCN与CTS相互作用产生变色反应的机理,认为其是在ZCN与CTS大分子间发生静电相互作用的基础上,主要由ZCN与CTS大分子间的疏水相互作用所引起.     

Fengycin interaction with lipid monolayers at the air-aqueous interface-implications for the effect of fengycin on biological membranes

In this study, we investigated the interaction of fengycin, a lipopeptide produced by Bacillus subtilis, with lipid monolayers using the Langmuir trough technique in combination with Brewster angle microscopy. Thermodynamic analyses were performed to get further information about the mixing behavior and the molecular interactions between the two components. The effect of fengycin on the structural and morphological characteristics of DPPC monolayers, as a simple model of biological membranes, depends on the fengycin molar ratio. With a small proportion of fengycin (X(f)0.1), the compressibility of the monolayer is modified but the morphological characteristics of the DPPC are not significantly affected. At an intermediate molar ratio (0.1相似文献   

A method for predicting the polarization of substances

A method for predicting the polarization characteristics of substances from the known permittivity and molar volume of parahydrogen (p-H₂), polarization characteristics of a reference, and the molar volume and internal interaction energy of the substance under study is suggested. The method is based on the assumption that the ratio between the deformation components of molar polarization at the given and critical temperatures is a universal function of reduced temperature.     

Condensed lamellar phase in ternary DNA-DLPC-cationic gemini surfactant system: a small-angle synchrotron X-ray diffraction study

We report on a small-angle synchrotron X-ray diffraction study of dilauroylphosphatidylcholine (DLPC) liposomes aggregated with high molecular DNA in the presence of 1,4-butanediammonium-N,N'-dilauryl-N,N,N',N'-tetramethyl gemini surfactant cations (C12GS). The aggregates prepared at the DLPC/C12GS/DNA phosphate group=2:1:1.6 molar ratio in 0.0015 mol x l(-1) NaCl aqueous solution exhibit Bragg reflections due to lamellar lipid bilayer stacking and the Bragg reflection typical of one-dimensional DNA lattice with parallel strands intercalated between lipid bilayers. In this condensed fluid lamellar L(alpha)(c) phase, the interactions between DNA and charged bilayers damp the thermally induced bilayer undulations. The diffraction data obtained with the mixture of DLPC liposomes and DNA (at DNA phosphate group/DLPC=0.8:1 molar ratio) indicate a DNA-lipid interaction in the absence of C12GS.     

DOPC/DPPC单层膜中分子间的相互作用及形态特征

利用Langmuir-Blodgett(LB)技术制备了不同表面压力下的1,2-二油酸-甘油-3-磷脂酰胆碱(DOPC)/1,2-二棕榈酸甘油-3-磷脂酰胆碱(DPPC)(摩尔比为1:1)和DOPC/DPPC/Chol(摩尔比为2:2:1)单层膜, 对单层膜内分子间的相互作用进行了热力学分析, 并用荧光显微镜和原子力显微镜对其形态进行了观测.热力学分析表明, DOPC与DPPC分子在单层膜结构中相互作用为排斥力, 诱导单层膜出现相变; DOPC, DPPC与胆固醇(Chol)间的相互作用均为吸引力, 当表面压力(π)大于18 mN/m时, DPPC与胆固醇的作用力大于DOPC.荧光显微镜观测表明, DOPC/DPPC单层膜出现明显相分离现象, 富含DPPC微区成“花形”结构, 且随着表面压力的升高微区逐渐增大, “花瓣”增多; 当胆固醇加入到DOPC/DPPC体系时, 单层膜相态由液相与凝胶相共存转变为液态无序相与液态有序相共存结构, 富含DPPC的微区形状从“花形”转变成“圆形”.原子力显微镜对单层膜的表征验证了荧光显微镜的观测结果, 表明胆固醇加入到DOPC/DPPC体系中对单层膜排列具有明显的影响, 压力和溶液状态等是影响脂膜结构的重要因素.     

Phase behavior and the partitioning of caveolin-1 scaffolding domain peptides in model lipid bilayers

The membrane binding and model lipid raft interaction of synthetic peptides derived from the caveolin scaffolding domain (CSD) of the protein caveolin-1 have been investigated. CSD peptides bind preferentially to liquid-disordered domains in model lipid bilayers composed of cholesterol and an equimolar ratio of dioleoylphosphatidylcholine (DOPC) and brain sphingomyelin. Three caveolin-1 peptides were studied: the scaffolding domain (residues 83-101), a water-insoluble construct containing residues 89-101, and a water-soluble construct containing residues 89-101. Confocal and fluorescence microscopy investigation shows that the caveolin-1 peptides bind to the more fluid cholesterol-poor phase. The binding of the water-soluble peptide to lipid bilayers was measured using fluorescence correlation spectroscopy (FCS). We measured molar partition coefficients of 10(4) M(-1) between the soluble peptide and phase-separated lipid bilayers and 10(3) M(-1) between the soluble peptide and bilayers with a single liquid phase. Partial phase diagrams for our phase-separating lipid mixture with added caveolin-1 peptides were measured using fluorescence microscopy. The water-soluble peptide did not change the phase morphology or the miscibility transition in giant unilamellar vesicles (GUVs); however, the water-insoluble and full-length CSD peptides lowered the liquid-liquid melting temperature.     

Effects of lipid chain length on molecular interactions between paclitaxel and phospholipid within model biomembranes

Molecular interactions between an anticancer drug, paclitaxel, and phosphatidylcholine (PC) of various chain lengths were investigated in the present work by the Langmuir film balance technique and differential scanning calorimetry (DSC). Both the lipid monolayer at the air-water interface and lipid bilayer vesicles (liposomes) were employed as model biological cell membranes. Measurement and analysis of the surface pressure versus molecular area curves of the mixed monolayers of phospholipids and paclitaxel under various molar ratio showed that phospholipids and paclitaxel formed a nonideal miscible system at the interface. Paclitaxel exerted an area-condensing effect on the lipid monolayer at small molecular surface areas and an area-expanding effect at large molecular areas, which could be explained by the intermolecular forces and geometric accommodation between the two components. Paclitaxel and phospholipids could form thermodynamically stable monolayer systems: the stability increased with the chain length in the order DMPC (C14:0)>DPPC (C16:0)>DSPC (C18:0). Investigation of paclitaxel penetration into the pure lipid monolayer showed that DMPC had a higher ability to incorporate paclitaxel and the critical surface pressure for paclitaxel penetration also increased with the chain length in the order DMPC>DPPC>DSPC. A similar trend was testified by DSC studies on vesicles of the mixed paclitaxel/phospholipids bilayer. Paclitaxel showed the greatest interaction with DMPC while little interaction could be measured in the paclitaxel/DSPC liposomes. Paclitaxel caused broadening of the main phase transition without significant change at the peak melting temperature of the phospholipid bilayers, which demonstrated that paclitaxel was localized in the outer hydrophobic cooperative zone of the bilayer. The interaction between paclitaxel and phospholipid was nonspecific and the dominant factor in this interaction was the van der Waals force or hydrophobic force. As the result of the lower net van der Waals interaction between hydrocarbon chains for the shorter acyl chains, paclitaxel interacted more readily with phospholipids of shorter chain length, which also increased the bilayer intermolecular spacing.