Behaviour of Water at Membrane Surfaces - a Molecular Dynamics Study

The molecular dynamics method was used to study the structure and dynamics of water above a layer of phosphatidylethanolamine headgroups, modelling the surface of a membrane. The simulation box contains one headgroup with sixteen ST2-water molecules. Planar periodic boundary conditions model a headgroup-water interface. The density distribution and the orientation profile along the layer normal were calculated. The water builds highly structured regions up to a ratio of ten water molecules per headgroup which compensate the dipole momenta of the lipids. The velocity, angular velocity and direction autocorrelation functions show that the bound water molecules oscillate around minimum potential positions at preferred hydration sites.