Collective Dynamics in Lipid Membranes: From Pore Formation to Flip-Flops

Abstract

Biological membranes are excellent examples of biologically relevant soft interfaces. They mediate or even govern a large variety of cellular functions [1–3]. Membranes serve as a host for membrane proteins to carry out their functions, and numerous signaling processes are either conducted inside membranes or mediated by them. Additionally, cellular membranes act as a permeability barrier, allowing only desired particles to permeate through the membrane into and out of the cell, besides which membranes are also involved in a variety of large-scale functions such as in maintaining the osmotic pressure and ion density gradients across the plasma membrane. The biological relevance of membranes is emphasized by the rather recently proposed lipid raft model [4–7], which essentially stresses the importance of understanding the interplay between lipids and proteins: membrane proteins function together with lipids. Consequently, lipid membrane structures, lipid domain coexistence, and especially the role of cholesterol in the structural properties of membranes have been paid a considerable amount of attention recently. Meanwhile, the dynamics of membranes [3,8,9] has received much less attention despite its substantial importance in, e.g., signaling, domain formation, and diffusion of lipids and proteins in the plane of the membrane.