Membrane heterogeneity : from lipid domains to curvature effects

Membrane heterogeneity on the micro- and nanometer scale plays an important role for a large number of biological processes. In parallel to the conception of refined membrane models, new experimental techniques to determine membrane microstructure were developed in recent years. Single molecule fluorescence has emerged as one of the leading technologies since it delivers the required spatial resolution and can be employed in living cells. In a complementary approach artificial model systems are used to study specific biophysical aspects of membranes in isolation and in a controllable way. In this thesis we show how phase separated artificial membranes can be used to gain fundamental insight into lipid composition based heterogeneity (Chap. 2) and membrane mediated interactions (Chap. 3). We demonstrate that those interactions can lead to lipid domain sorting (Chap. 4). Experiments with artificial membranes are complemented with live cell studies. We develop a robust analysis method for single molecule position data (Chap. 5) and use it to study the role of heterogeneity in cell signaling (Chap. 6). Finally, we show how protein cluster formation can be measured by counting single molecules in live cells (Chap. 7).