ION BINDING TO CHARGED PHOSPHOLIPID MEMBRANES

多价阳离子，特别是钙，与 生物膜在许多生物现象中是最重要的， 例如神经兴奋性、肌肉收缩调节、胞吐 化学递质的释放，血液凝固， 组织. 在这个项目中，这些离子与 生物膜的磷脂成分将被研究， 实验和理论上。 重点将放在数量上 钙与磷脂酰肌醇膜结合的说明 (PI)和磷脂酰丝氨酸（PS），这是主要的负电荷 细胞内膜和细胞质膜的磷脂， 分别 PI还参与细胞内的 Ca++。 其目的是为以下基本问题提供答案 问题：（1）什么是钙离子：磷脂结合的化学计量 PI和PS？ (2)阴离子与PI和PS膜结合吗？ (3)Ca++是否 与单价阳离子竞争PI和PS结合位点？ (4)Ca++是否 竞争或取代质子从PI和PS结合位点？ 相同的 问题将解决的PI和PS混合物制成的膜， 中性磷脂，含磷酸化PI的膜 衍生物，从骶质网膜提取的脂质，和 除了Ca++之外的二价阳离子。 实验将分为三类： (1)平面双层类脂膜的静电表面电位 通过使用Monazomycin进行监测，Monazomycin是一种表面电位敏感的 电导探针 (2)将使用粒子电泳来确定 在此条件下，磷脂囊泡被 吸附离子 (3)pH-stat和Ca-stat测量将检测Ca++-H+ 竞争效应。 在所有实验中变化的参数为： (a)多价阳离子浓度和种类，（B）单价阳离子 （c）阴离子浓度和种类，包括 离液阴离子，（d）pH，（e）膜电荷密度，（f）脂质种类。 设计条件以优化实验对每种 将采用上述问题。 数据将通过使用 申请人先前发表的理论，其处理1：1和1：2两者 二价阳离子结合化学计量以及竞争性和 二价和单价阳离子与磷脂的非竞争性结合 膜。 该理论将扩展到包括阴离子和质子结合 现象。

The interaction of multivalent cations, particularly calcium, with biological membranes is of primary importance in many biological phenomena, such as nerve excitability, regulation of muscle contraction, exocytotic discharge of chemical transmitters, blood clotting, and mineralization of tissue. In this project the interactions of such ions with the phospholipid component of biological membranes will be studied, both experimentally and theoretically. Emphasis will be placed on quantitative elucidation of the binding of calcium to membranes of phosphatidylinositol (PI) and phosphatidylserine (PS), which are the major negatively-charged phospholipids of intracellular membranes and of cell plasma membranes, respectively. PI is also involved in the mobilization of intracellular Ca++. The aim is to provide answers to the following fundamental questions: (1) What is the ion:phospholipid stoichiometry of Ca++ binding to PI and PS? (2) Do anions bind to PI and PS membranes? (3) Does Ca++ compete with monovalent cations for PI and PS binding sites? (4) Does Ca++ compete with or displace protons from PI and PS binding sites? The same questions will be addressed to membranes made of PI and PS mixtures with neutral phospholipids, to membranes containing phosphorylated PI derivatives, to lipids extracted from sacroplasmic reticulum membranes, and to divalent cations other than Ca++. Experiments will be of three types: (1) Electrostatic surface potentials of planar bilayer lipid membranes will be monitored by use of monazomycin, a surface-potential-sensitive conductance probe. (2) Particle electrophoresis will be used to determine conditions under which phospholipid vesicles are exactly neutralized by adsorbed ions. (3) pH-stat and Ca-stat measurements will detect Ca++-H+ competition effects. The parameters to be varied in all experiments are: (a) multivalent-cation concentration and species, (b) monovalent-cation concentration and species, (c) anion concentration and species, including chaotropic anions, (d) pH, (e) membrane charge density, (f) lipid species. Conditions designed to optimize experimental sensitivity to each of the questions posed above will be employed. Data will be analyzed by use of a theory, previously published by the applicant, that treats both 1:1 and 1:2 divalent-cation binding stoichiometries as well as both competitive and non-competitive binding of divalent and monovalent cations to phospholipid membranes. The theory will be extended to include anion and proton binding phenomena.