(121b) Effect of Transmembrane Distribution of Fluid-Gel Patterned Bilayers

Molecular dynamics simulations are used to provide insights on the molecular scale structure of two component lipid bilayers in the fluid state and in coexisting gel-fluid patterned bilayers. This is a promising and emerging area to explore since the understanding of the patterns at the molecular scale has implications for the mechanisms by which cell membranes maintain their two dimensional structure and how this structure is related to their function. We show that in fluid phase coexisting bilayers the higher melting lipid prefers to partially self-associate favoring intermonolayer coupling. On the other side, uncoupled monolayers are metastable and evolve to a stable state by diffusion in the μs time scale. For fluid bilayers a non-random distribution is observed, favoring a transbilayer complementarity of phospholipids, which is in agreement with experimental observations. This molecular level approach allows controlling the patterning of gel-fluid bilayers by changing the composition and the temperature; this may suggest a mechanism by which real cell membranes maintain their suprastructure.