The Lateral Stress Profiles of Lipid Bilayers Compared with Spontaneous Lipid Curvature Using Computer Simulations

Abstract

For transmembrane protein folding, it is hypothesized that the lateral stress profile of the lipid bilayer is an important factor for comparing protein conformations, such as the open and closed states of a channel. For example, according to this theory, the positive pressure at the bilayer interior and negative pressure at the bilayer surface stabilize protein conformations with an hourglass shape. However, the lipid-dependent lateral stress profile of a lipid bilayer is not directly measurable by experiment, but rather is inferred, e.g., from the spontaneous curvature of its constituent lipids, a geometric parameter that may be measured by x-ray scattering of the hexagonal phase of lipid/water systems. The lateral stress profile of model bilayers may be measured by computer simulations, in this work using the latest all-atom lipid CHARMM forcefield. By simulating both the fluid bilayer and hexagonal phases of lipid systems with varied spontaneous curvature, we seek to bridge the gap between experimentally measured spontaneous curvature of lipids and their characteristic bilayer lateral stress profile.