Prof. James Kindt, Emory University

Atomistic simulation of mixed-lipid bilayers: Mixed methods for mixed membranes

AACP Seminar Series

Biomembranes typically contain a diverse array of lipids with variations in both polar headgroup and hydrophobic tail compositions. This diversity raises the question of how lipids of different type are laterally distributed within these membranes: how strongly might the local lipid composition in the membrane vary according to microenvironmental factors? Computer simulation is useful, in conjunction with experiments, to address this fundamental question within simple binary and ternary lipid bilayer model membranes. As the timescale for lipid mixing and demixing remains longer than practical trajectory times for conventional molecular dynamics simulations, adding Monte Carlo steps to a dynamics simulation provides is useful to allow an equilibrium lateral distribution of lipids to be achieved, and has facilitated the study of several mixtures in different microenvironments. In simulations where the difference between lipid structure was solely one of tail length, local environment influenced local composition strongly at edge defects, weakly in the neighborhood of a transmembrane helical peptide, and to no measurable extent in a curved bilayer. Mixed Monte Carlo/molecular dynamics simulations have furthermore shed light on the phenomenon of lipid sorting according to tail saturation between high- and low-cholesterol domains in a ternary system that is a model for the “raft” structures widely believed to be present in cell membranes.

For more information contact Prof. Angelo Bongiorno (404-385-5169).