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Soft Matter and Biological Physics
Eur. Phys. J. E 11, 21-28 (2003)
DOI: 10.1140/epje/i2002-10125-x

Lateral and transverse diffusion in two-component bilayer membranes

A. Imparato, J.C. Shillcock and R. Lipowsky

Max-Planck-Institut für Kolloid- und Grenzflächenforschung, Abteilung Theorie, D-14424 Potsdam, Germany

imparato@mpikg-golm.mpg.de
shillcock@mpikg-golm.mpg.de
lipowsky@mpikg-golm.mpg.de

(Received 6 December 2002 and Received in final form 26 March 2003 / Published online: 27 May 2003)

Abstract
We study the lateral and transverse diffusion of amphiphiles in two-component bilayer membranes, using a coarse-grained model for amphiphilic molecules and combined Monte Carlo-Molecular Dynamics simulations. Membrane structural properties, such as the mean thickness, are also measured. The dependence of such properties on membrane composition, inter-molecular interactions, and amphiphile stiffness is determined. In particular, we show that addition of shorter amphiphiles drives the model membrane towards a more fluid state, with increased amphiphile lateral diffusion rates. These results can be understood in the framework of a simple free-volume model. Furthermore, we observe an increase in the trans-membrane diffusion when the interaction energy of amphiphiles with their neighboring molecules is decreased.

PACS
82.70.-y - Disperse systems; complex fluids.
61.20.Ja - Computer simulation of liquid structure.

© EDP Sciences, Società Italiana di Fisica, Springer-Verlag 2003