PHASE-FIELD SIMULATIONS OF THE MORPHOLOGICAL EVOLUTION OF LIPID BILAYER MEMBRAN

这个子项目是利用资源的许多研究子项目之一。 由NIH/NCRR资助的中心拨款提供。对子项目的主要支持 子项目的首席调查员可能是由其他来源提供的， 包括美国国立卫生研究院的其他来源。为子项目列出的总成本可能 表示该子项目使用的中心基础设施的估计数量， 不是由NCRR赠款提供给次级项目或次级项目工作人员的直接资金。 生物膜是由多种脂类和蛋白质组成的结构。脂类只通过疏水作用结合在一起，形成一种类似液体的结构。质膜是包围所有哺乳动物细胞的脂质双层膜，它不是均匀的，而是包含被称为木筏的区域，定义为富含胆固醇和饱和脂质的区域。对于细胞生物学家和免疫学家来说，了解这些木筏的形成方式和原因是非常重要的，因为它们参与了许多重要的细胞功能和过程，包括内吞作用、细胞黏附、信号传递、蛋白质组织、脂质调节和病原体感染。这些浮筏结构还显示出巨大的技术应用潜力，特别是在生物传感器和药物输送系统方面。我们研究了多组分脂质双层膜的相分离(脂筏形成)和形态演变。该模型适用于具有平面和球形背景几何形状的膜，分别模拟膜的近平面部分或整个囊泡。该模型处理每个双层小叶的单独成分，这决定了自发曲率。膜的组成和形状与修改的Helfrich自由能偶联，其包括小叶组合物之间的偶联。成分演化用相场方法模拟，用Cahn-Hilliard方程描述，形状变化用弛豫动力学描述。对于接近平面的双层体系，我们在组成空间中构造了一个平衡形态相的相图，其中有几个小叶耦合强度的值。对于使用球形背景建模的囊泡，我们的研究集中在自发曲率效应如何影响动力学。

This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. Primary support for the subproject and the subproject's principal investigator may have been provided by other sources, including other NIH sources. The Total Cost listed for the subproject likely represents the estimated amount of Center infrastructure utilized by the subproject, not direct funding provided by the NCRR grant to the subproject or subproject staff. Biological membranes are structures composed of multiple lipid species and proteins. The lipids are bound only through hydrophobic interactions, creating a liquid-like structure. The plasma membrane, a lipid bilayer membrane surrounding all mammalian cells, is not homogeneous, but rather contains domains termed rafts, defined as regions enriched with cholesterol and saturated lipids. Understanding how and why these rafts form is of great importance to cell biologists and immunologists, since they are involved in many important cell functions and processes including endocytosis, cell adhesion, signaling, protein organization, lipid regulation, and infection by pathogens. These raft structures also show great potential for technological applications, especially in connection with biosensors and drug delivery systems. We examine phase separation (lipid raft formation) and morphological evolution of multicomponent lipid bilayer membranes. The model applies to membranes with planar and spherical background geometries, simulating a nearly planar portion of a membrane or an entire vesicle, respectively. The model treats the individual composition of each bilayer leaflet, which determines the spontaneous curvature. The compositions and shape of the membrane are coupled with a modified Helfrich free energy, which includes coupling between the leaflets compositions. The compositional evolution is modeled using a phase-field method and is described by a Cahn-Hilliard-type equation, while the shape changes are described by relaxation dynamics. For nearly planar bilayer systems we construct a phase diagram of equilibrium morphological phases in the composition space for a few values of the strength of the leaflet coupling. For vesicles modeled using a spherical background, our investigations have focused on how the dynamics are affected by spontaneous curvature effects.