Experimentally characterizing the origins of confinement effects in membranes.

Abstract

Diffusion in membranes plays a vital role in biological processes, governing reaction rates and reconfiguring membranes. The effect of crowding and inhomogeneity on the dynamics of lipids and proteins is substantial, but the underlying physical principles are not well understood. We investigate the effect of confinement on the two-dimensional diffusion of model lipids in supported bilayers using a novel lithographically-defined platform. Specifically, we explore how changing the geometry of escape routes influences the diffusion of confined lipids. We compare lipid diffusion through narrow escape funnels formed by wide range of structures, enabling us to systematically explore the effect of confinement size and geometry. Our results demonstrate that the local geometry, not just the size of the escape funnel, determines the characteristic diffusion timescale. Our approach enables us to directly test several competing theoretical descriptions, and demonstrates the utility of our simple, highly-customizable diffusion characterization platform.