Structure, shape and dynamics of biological membranes.

Cells use membranes as their boundary, shielding their inside from the outside world, and to create internal structure. The different membranes in a cell have large variations in chemical composition, elasticity, shape and function. In contrast with the standard static picture often shown in cartoons, membranes are moreover one of the most dynamic components of the cell. Based on a detailed study of the structure and shape of various membranes we have developed techniques to measure the relevant physical parameters. Using these, we can directly couple the structure and shape to the function of the membrane. Combining these studies with studies of the membrane dynamics we find that membranes can spontaneously demix in different domains, which can interact with each other by forces mediated by the membrane itself. This interaction results in a sorting of the domains by size. Introducing an active element, molecular motors, into the system, we find that new structures are formed. An example of such a structure is a long membrane tube. These tubes also exhibit rich dynamics, and oscillating growth and shrink patters, which makes them suitable length and shape regulators in living cells.LEI Universiteit LeidenStichting voor Fundamenteel Onderzoek der Materie (FOM).Theoretical Physic