Influence of Cholesterol on Phase Behavior and Nonrandom Mixing of Membrane Components

本项目的总体目标是了解胆固醇在生物膜中的作用。这个项目有四个主要的概念要素：(I)含有胆固醇的三组分脂质混合物将作为哺乳动物质膜的化学简单实验模型；(Ii)将使用几种独立的、互补的方法来彻底绘制和表征这些模型膜的组成相行为；(Iii)基于观察到的相行为，将使用蒙特卡罗模拟来寻找主要的微观脂-脂相互作用能；以及(Iv)将在这些表征良好的系统中研究其他膜组分的横向分布，从而揭示富含胆固醇的“耐洗涤剂膜”的性质。在实验上，该项目包括：X射线衍射，以寻找相边界；电子自旋共振，以绘制相的有序性参数；芘准分子/单体比率和荧光共振能量转移，以找到相边界并测量相之间的分配；共焦荧光显微镜，以可视化共存相；以及计算机模拟，以评估微观相互作用模型的热力学含义，并生成横向分布的图像。虽然胆固醇是哺乳动物质膜中含量最丰富的单一类脂物种，但其与邻近膜分子相互作用的潜在本质仍不清楚。这项研究将对这些潜在的脂-脂相互作用提供深入的物理理解，因此可能对信号转导领域产生非常重要的影响。

Feigenson, Gerald W.MCB 0077630The overall goal of this project is to understand the role of cholesterol in biological membranes. This project has four main conceptual elements: (i) 3-component lipid mixtures, containing cholesterol, will serve as chemically simple experimental models of mammalian plasma membranes; (ii) Several independent, complementary methods will be used to thoroughly map and characterize the compositional phase behavior of these model membranes; (iii) Based on the observed phase behavior, Monte Carlo simulations will be used to find the dominant microscopic lipid-lipid interaction energies; and (iv) The lateral distributions of other membrane components will be studied in these well-characterized systems, shedding light on the nature of cholesterol-rich "detergent resistant membranes." Experimentally, this project involves x-ray diffraction to find phase boundaries; electron spin resonance to map order parameters of the phases; pyrene excimer/monomer ratios and fluorescence resonance energy transfer to find phase boundaries and to measure partitioning between phases; confocal fluorescence microscopy to visualize coexisting phases; and computer simulations to evaluate the thermodynamic implications of microscopic interaction models and to generate pictures of lateral distributions. Although cholesterol is the single most abundant lipid species in mammalian plasma membranes, the underlying nature of its interactions with neighboring membrane molecules has remained obscure. This research will provide an in-depth physical understanding of these underlying lipid-lipid interactions and could therefore have a very significant impact on the field of signal transduction.