8th Liquid Matter Conference September 6-10, 2011 Wien, Austria ...

Tue 611:23-14:00P10.35Membrane lateral structure: how immobilized particlescan stabilize small domainsRichard Vink 1 and Timo Fischer 11 Institute of Theoretical Physics, Georg-August-Universität Göttingen, 37077, Göttingen,GermanyMembranes are two-dimensional fluid environments, consisting of lipids and proteins [1]. Inmodel membranes, macroscopic phase separation is routinely observed, but not so in biologicalmembranes. Instead, the lateral structure of a biological membrane is characterized by smalldomains [2]. This poses an interesting puzzle because a structure of small domains inevitablyimplies a large amount of interface, which is unfavorable because of line tension [3]. In thiscontribution, it is shown that immobilized protein obstacles provide a mechanism to compensatethe cost of line tension. The presence of such obstacles in biological membranes is known tooccur, and arises from interactions with the underlying cytoskeleton. I will present results fromcomputer simulation, which indeed show that a structure of small domains becomes stable,already at low concentrations of quenched obstacles [4]. In addition, these results confirm afundamental conjecture of de Gennes [5], stating that a fluid with quenched obstacles belongs tothe universality class of the random-field Ising model.[1] The fluid mosaic model of the structure of cell membranes., S. J. Singer and G. L.Nicolson, Science 175, 720 (1972).[2] Functional rafts in cell membranes, K. Simons and E. Ikonen, Nature 387, 569 (1997).[3] Physics puzzles on membrane domains posed by cell biology, Pierre-Francois Lenne and AliceNicolas, Soft Matter 5, 2841 (2009).[4] Domain formation in membranes with quenched protein obstacles: Lateral heterogeneity andthe connection to universality classes, T. Fischer and R. L. C. Vink, J. Chem. Phys. 134, 055106(2011).[5] Liquid-liquid demixing inside a rigid network: qualitative features, P. G. de Gennes, J. Phys.Chem. 88, 6469 (1984).35