Effective Bending Rigidity of Membranes with Rigid Inclusions

Abstract

The ability of biological membranes to bend and deform is essential to a wide range of cell processes. Significant advances in understanding the elasticity of lipid bilayers underlying these deformations have been made by studying homogeneous fluid membranes. However, biological membranes are far from homogeneous, and less is known about how the heterogeneity affects the material properties of the membrane. Here we use neutron spin echo spectroscopy (NSE) to study the effective bending rigidity (κeff) of heterogeneous lipid membranes with coexisting rigid gel and soft fluid domains. Our data show that κeff scales directly, but not linearly, with the area faction of gel phase and are in excellent agreement with theoretical predictions for heterogeneous lipid membranes with rigid inclusions. While it is intuitively expected that κeff should in some way depend on the fraction of gel phase, the functional form of the scaling has important implications for understanding the effects of rigid inclusions, such as proteins or lipid domains, on the effective stiffness of biological membranes.