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Regensburg 2004 – scientific programme

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AKB: Biologische Physik

AKB 50: Poster Session "Biological Physics"

AKB 50.18: Poster

Friday, March 12, 2004, 10:30–13:00, B

Mechanism of Model Membrane Fusion Determined from Monte Carlo Simulation — •Marcus Mueller1, Kirill Katsov2, and Michael Schick21Institut fuer Physik, WA331, Johannes Gutenberg Universitaet, D55099 Mainz, Germany — 2Dept. of Physics, University of Washington, Seattle, WA 98195-1560, USA

Fusion of membranes is essential to living systems, but its mechanism is not well understood. We have carried out extensive Monte Carlo simulations of the fusion of tense apposed bilayers formed by amphiphilic molecules within the framework of a coarse grained lattice model. Our model exhibits a phase diagram which is similar to that of biological lipids. The fusion pathway, however, differs from the “hemifusion hypothesis”.

First stalks form between the apposed bilayers, but rather than expanding radially to form an axial-symmetric hemifusion diaphragm of the cis leaves of both bilayers, they promote hole nucleation of the bilayers in their vicinity. Two subsequent paths are observed: (i) A second hole is formed in the opposite bilayer, and the stalk aligns both hole as it encircles them and forms the fusion pore. (ii) The stalk encircles the hole completely before a second hole is formed in the opposite bilayer. A diphragm is formed out of both leaves of the intact bilayer. The rupture of this diaphragm completes fusion. Both pathways give rise to an increase in mixing between the cis and trans leaves of the bilayer and allow for leakage.

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