Berlin 2005 – wissenschaftliches Programm

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AKB: Biologische Physik

AKB 100: Poster Session I

AKB 100.80: Poster

Samstag, 5. März 2005, 16:45–18:45, Poster TU D

Monte Carlo Simulation of Lipid Bilayers with Rigid Inclusions — •Olaf Lenz und Friederike Schmid — Universität Bielefeld, Fakultät für Physik

We have investigated the effects of inclusions (for example proteins) on a lipid bilayer close to it’s fluid–gel (main) transition on a mesoscopic scale of a few tens of nanometers by means of a coarse-grained Monte-Carlo simulation.

We use a very efficient and simple bead-spring model of one hydrophilic head bead connected to six hydrophobic tail beads for the lipids and a model of  “phantom” solvent beads that do not interact with each other for the solvent environment. In this model, the lipids self-assemble to form a lipid bilayer and the bilayer exhibits the fluid–gel transition. We observe a tilted gel state and an “interlocked” gel state which possibly is related to the well-known “ripple phase” of bilayers. The inclusions are represented by rigid, hydrophobic cylinders that roughly correspond to α-helices.

In the liquid phase, an ordering of the lipid tails is induced in the vicinity of the rigid inclusion. Close to the phase transition, the range of this effect grows. In the tilted gel phase, a long-ranged, directed point defect of the lipid tail ordering was observed. This defect leads to the destruction of the gel phase and therefore shifts the critical temperature of the phase transition to lower temperatures. Furthermore, the defect is expected to strongly influence the interaction between inclusions on a scale of a few times the size of the inclusion.