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BP: Fachverband Biologische Physik

BP 19: Biological Membranes II

BP 19.3: Talk

Tuesday, March 15, 2011, 14:30–14:45, ZEU 260

Surface viscosity and intermonolayer friction in a soft, solvent-free model of lipid bilayers — •Martin Hömberg and Marcus Müller — Institut für Theoretische Physik, Georg-August-Universität, 37077 Göttingen, Germany

In coarse-grained models of lipid bilayers one integrates out several microscopic degrees of freedom so that the study of membranes comprising thousands of lipids becomes feasible in computer simulations. Thermodynamical, structural, and mechanical properties of biological bilayers can be accurately reproduced in these models. However, the coarse-graining also eliminates degrees of freedom that should appear in the coarse-grained dynamics as dissipation and thermal noise. Hence, the coarse-grained and the actual dynamics may differ severely.

Here we employ a solvent-free, coarse-grained model to analyze two dynamical quantities: the surface viscosity and the intermonolayer friction. We compare the surface viscosity obtained within a Green-Kubo approach with the one obtained from reverse NEMD simulations. The measurement of the intermonolayer friction differs from experiments and simulations with an explicit solvent, therefore we are using a modified version of the SL-theory of the dynamics of bilayer undulations and another Green-Kubo approach for obtaining it.

Finally, we discuss how to map our bead-spring model onto a two-dimensional model of coupled monolayers where the lipids are represented by point particles. The interactions and the thermostat are tuned so that it reproduces the RDF and the structure factor, but more importantly also the surface viscosity and the intermonolayer friction.