A VORONOI ANALYSIS OF LIPID AREA FLUCTUATION IN A BILAYER

Membrane area fluctuation of the lipid bilayer has been investigated b ased upon two-dimensional Voronoi tessellation analysis for the center s of mass of the lipid molecules projected on the bilayer plane. Long- time trajectories of the molecules used in the analysis have been gene rated by molecular dynamics calculations. The single-molecular area de fined by Voronoi polygon showed a broad Gaussian distribution, from wh ich area distribution of the membrane composed of N lipid molecules ma y satisfactorily be predicted. The fluctuation was found to be caused mainly by thermal motions of the alkyl chains. The number of gauche co nformation and alkyl chain length was strongly correlated to the molec ular area. Head group motions, however, showed little contribution to the fluctuation. Geometry of Voronoi polygons and the number of neares t neighbor molecules showed rather broad distribution due to the therm al fluctuation. This is in contrast to the structure found in the ripp le, gel, and crystal phases. Formation of large pores in the membrane was also investigated. (C) 1998 American Institute of Physics.