The permeability of a lipid bilayer

Abstract

This work presents results on the permeability of a lipid bilayer to water molecules. We look at the change in bilayer permeability as a function of lipid structure and area per lipid molecule. A molecular dynamic simulation (MDS) of a solvent surfactant system was used in the canonical ensemble to simulate the membranes. Permeability was obtained by calculating the permeative resistance. This method, developed by Marrink and Berendsen, allows the sampling of very long time scale events on short time scale simulations. The structural properties of the simulated bilayer are studied and compared both to atomistic MDS and experiments. The elasticity of the simulated membranes are shown to be in good agreement with experimental results. The permeation is found to increase only slightly for a relative stretch of up to 20%, a result which is qualitatively similar to recent experiments. The increase is described by a linear relation between the permeability and the relative extension. Most of the changes in the lipid bilayer are found to occur in the central part near the ends of the tails. The effect of lipid packing on bilayer permeability are also discussed.