Lateral Pressure Profile in a Lipid Membrane with Curvature: Analytical Expression

Abstract

Analytic expression for the lateral pressure distribution in a curved lipid bilayer is derived: P(z)=P0(z)+ (a(z)-a0)dP(z)/da0, as function of the depth z across bilayer, using the flexible strings model of lipid chains developed earlier [1]. P0(z) is flat bilayer lateral pressure profile [1], a(z) and a0 is area/per lipid in the curved and flat bilayer respectively. In the figure the plots confine to the hydrophobic part of each monolayer. Solid line is lateral pressure profile in a spherical vesicle of thickness 15 Å and curvature radius 1000 Å. Dashed line is the pressure profile in a flat bilayer of the same thickness. Z=0,2L mark the neutral surfaces between headgroups and tails (see left sketch), where flat membrane's area per lipid is conserved. Right insert shows a symmetry breaking distortion of the pressure profile caused by curvature. Hence, distinctly from the flat bilayer, the lateral pressure profile in vesicle is asymmetric with respect to the monolayers interface, as was found in [2] using molecular dynamics.