ABSTRACT
Giant vesicles respond to environmental changes by remodeling both their shape and their local membrane composition. Particularly interesting morphological transitions are provided by budding and tubulation which are governed by curvature elasticity. The latter elasticity can also be used to understand membrane fission even though this process represents a topological transformation. The remodeling of membrane composition can arise from ambience-induced segmentation of membranes or from domain formation via lipid phase separation. A simple example for ambience-induced segmentation is provided by vesicle adhesion, which is intimately related to the endocytosis of nanoparticles. Lipid phase separation leads to stable multi-domain patterns and to morphological transitions that change both the vesicle shape and the domain pattern. Liquid droplets at vesicles undergo wetting transitions, generate curvature by capillary forces, and act as soft scaffolds. All of these membrane-related processes can be understood in terms of a few fluid-elastic parameters: the membranes’ bending rigidities and spontaneous curvatures, the adhesive strength between membranes and substrate surfaces, the line tension of domain boundaries, and the interfacial tension of liquid droplets. The theory described here has been primarily scrutinized by experimental observations on lipid bilayers but applies to lipid-protein membranes as well.
