Molecular dynamics simulation of a bilayer membrane

Abstract

We have applied the computer simulation method of molecular dynamics (MD) to a realistic representation of a lipid bilayer, which serves as a model for a biological membrane. The bilayer consists of 2×16 decanoate molecules and is periodic in two dimensions. Interactions include Lennard-Jones, dihedral, and bond angle potentials while bond lengths are constrained. Head groups are confined near the bilayer surfaces by harmonic forces representing their interaction with the water layer. After equilibration, a simulation extending over 80 ps at 300 K was carried out for a head group surface area of 25 Å2. Experimental order parameters are perfectly reproduced. A highly interesting cooperative tilt of the molecules, persisting over several tens of picoseconds, is observed. The molecular plane is strongly correlated with the plane of tilt. The popular kink model for the hydrocarbon chain order and dynamics is not supported. In view of the observed extended spatial correlation, a simulation was also carried out for a bilayer consisting of 2×64 decanoate molecules.