An Investigation into the Dynamic Behavior of Coarse Grain Models for Lipid Bilayer Systems.


Hirsh Nanda, Susan Krueger, Joseph E. Curtis


The limitations in time and length scales attainable with traditional all atom molecular dynamics simulations is a major motivation for the development of coarse grain (CG) molecular models.  The application of these models for lipid systems is of particular interest because of long relaxation times of lipid molecules and proteins imbedded in the lipid  matrix.  Impressive efforts by several groups [J. Phys. Chem. B, 2001 (105) p.4464;  J. Phys. Chem. B, 2004 (108) p.750] have developed CG models capable of reproducing many membrane structure and phase properties.  We are interested in the use of coarse-grain simulations to study the dynamics of lipid membranes and their relation to membrane structural properties at the mesoscopic level.  Our current work has focused on validating the semi-quantitative nature of the dynamics of DOPC lipid membrane bilayers by comparison of coarse-grain simulations to previously validated all-atom simulations.  From these simulations neutron scattering observables of specific molecular groups were calculated.  We find that at least in one CG methodology that the relaxations of some groups do not match all atom simulations on the nanosecond time scale.  From our work we hope to improve upon current coarse grain models as well as stimulate future neutron experiments.