Crystalline, Ordered and Disordered Lipid Membranes: Convergence of Stress Profiles due to Ergosterol

We present a simulation study focusing on modulations of the stress, or lateral pressure, profiles of lipid bilayer phases by addition of a sterol, ergosterol, at multiple temperatures. A major redistribution of lateral and normal pressures across the gel-phase bilayer required 10 mol % sterol in comparison to a gradual redistribution beginning at 20 mol % for the liquid phase. Stress profiles across all temperatures converged at 30 mol % ergosterol. Redistribution and merging of stress profiles, associated with structural alterations, are coincident with experimentally observed modulations in mechanical properties and therefore are suggested as the mechanism of action for this biologically necessary role of sterols.