ION BINDING TO CHARGED PHOSPHOLIPID MEMBRANES

多价阳离子，特别是钙离子与 生物膜在许多生物现象中起着至关重要的作用， 如神经兴奋性、肌肉收缩调节、胞吐 化学传递物的排放、血液凝结和矿化 组织。在这个项目中，这些离子与 将研究生物膜的磷脂成分，两者都 从实验和理论上都是如此。重点将放在数量上 钙与磷脂酰肌醇结合膜的阐明 (PI)和磷脂酰丝氨酸(PS)，这是主要的负电荷 胞内膜和细胞质膜的磷脂， 分别进行了分析。PI也参与了细胞内的动员 CA++。其目的是为以下基本问题提供答案 问题：(1)什么是离子：钙离子结合的磷脂化学计量 (2)阴离子与PI和PS膜结合吗？(3)Ca++与膜结合吗？ 与单价阳离子竞争PI和PS结合部位？(4)Ca++ 与PI和PS结合部位的质子竞争或取代？相同 问题将解决由PI和PS混合物制成的膜 中性磷脂到含有磷酸化聚酰亚胺的膜 从骶质网膜中提取的脂质的衍生物，以及 除Ca++外的其他二价阳离子。实验将有三种类型： (1)平面双层类脂膜的静电表面电势 通过使用表面电位敏感的单氮霉素进行监测 电导探头。(2)采用颗粒电泳法测定 磷脂囊泡被完全中和的条件 被吸附的离子。(3)pH-STAT和Ca-STAT测量将检测到Ca++-H+ 竞争效应。在所有实验中要改变的参数是： (A)多价阳离子浓度和物种，(B)一价阳离子 浓度和物种；(C)阴离子浓度和物种，包括 杂化阴离子，(D)pH，(E)膜电荷密度，(F)脂质种类。 设计用于优化实验灵敏度的条件 上面提出的问题将被采用。数据将通过使用 申请人以前发表的同时处理1：1和1：2的理论 二价阳离子结合化学计量学以及竞争性和 二价阳离子和一价阳离子与磷脂的非竞争性结合 膜。这一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.