Cholesterol Precipitation from Real and Model Biomembranes

9722818费根森这项工作的一个目标是找到胆固醇在模型和真实生物膜中的溶解极限，超过这个极限，胆固醇以晶体的形式从双层中沉淀出来。该项目由四个主要部分组成：(1)明确的胆固醇和磷脂混合物被用作生物膜的模型；(2)开发出新的方法并结合X射线衍射实验对共存相的形成很敏感；(3)使用蒙特卡罗计算机模拟以求出胆固醇和磷脂在整个组成范围内的相互作用能；(4)在培养的哺乳动物细胞中探索胆固醇一水合物的形成。这些实验将使构建描述胆固醇与两种不同磷脂混合的三组分相图成为可能。这个项目的理论部分开发了一个模型来描述胆固醇与其邻近的脂类之间的微观相互作用能。在这些模型系统研究的指导下，培养细胞的X射线衍射以及电子和光学显微镜将确定胆固醇在真实生物膜中的溶解极限。该项目的总体目标是定义和测量特定膜的过量胆固醇含量。这些基础研究将阐明胆固醇在细胞内积累的机制和细胞吸收胆固醇的信号。***

9722818 Feigenson A goal of this work is to find the solubility limit of cholesterol in model and real biomembranes, above which cholesterol precipitates from the bilayer as a crystal. This project has four main components: (I) defined mixtures of cholesterol and phospholipids are used as models for biomembranes; (ii) novel methods, together with X-ray diffraction experiments, are developed that are sensitive to the formation of coexisting phases; (iii) Monte Carlo computer simulations are used in order to find the cholesterol and phospholipid interaction energy over the entire range of compositions; (iv) crystalline cholesterol monohydrate formation is probed in cultured mammalian cells. These experiments will enable construction of 3-component phase diagrams that describe the mixing of cholesterol with two different phospholipids. The theoretical part of this project develops a model to describe the microscopic interaction energy between cholesterol and its neighboring lipids. Guided by these model system studies, X-ray diffraction and electron and optical microscopy of cells in culture will determine cholesterol solubility limits in real biomembranes. The overall objective of this project is to define and measure excessive cholesterol content, for a given membrane. These basic studies will clarify mechanisms of cholesterol accumulation within cells and cellular signals for its uptake. ***