Lipids as Regulators of Effective Membrane Rigidity

Abstract

The rigidity of lipid bilayer, the structural core of all cellular membranes, is one of the key force factor in membrane remodeling. For most of “biomimetic” lipid compositions the rigidity is thought to be only a weak function of the composition. However, for multicomponent membranes the composition is coupled to geometry, resulting in lateral redistribution of components in curvature gradients. Such redistribution can substantially facilitate local membrane deformations. We detected that such a decrease of apparent membrane rigidity in pure lipid bilayers containing physiological amounts of dioleoylphosphotidylethanolamin (DOPE), the lipid characterized by highly negative intrinsic curvature. Analyzing fast shape transformations of membrane nanotubes containing different amounts of DOPE we found that the membrane softening followed concentration-dependent redistribution of DOPE towards negative membrane curvature. The apparent bending rigidity of DOPE-containing membranes decreased almost twofold at 30mol% of DOPE, indicating that similar amount of DOPE in cellular membranes can substantially facilitate deformations.