HEAD GROUP AND CHAIN BEHAVIOR IN BIOLOGICAL-MEMBRANES - A MOLECULAR-DYNAMICS COMPUTER-SIMULATION

A computer-modeled hydrated bilayer model of the lipid 2,3-dimyristoyl -D-glycero-1-phosphorylcholine in the L(alpha), phase was built. Parti cular care was taken in building the starting structure with the inclu sion of structural detail reported in experiments on the L(alpha) phas e. Molecular dynamics simulations using the molecular dynamics and ene rgy refinement program AMBER 3.1 force field with an optimized paramet ers for liquid simulation parameter set were run to study the motions and conformations of the lipid molecules and characterize the behavior and structure of the head groups and the hydrocarbon lipid chains. Al though the head groups were observed to show great flexibility, certai n head-group torsion combinations appeared favored. The observed tilt of the lipid chains is discussed and is consistent with previous exper imental findings. Motion of the lipid chains is shown to be correlated with those chains immediately surrounding, but correlation with chain s more distant varies with time.