Anomalous Behavior in Lipid Bilayer Membranes

Abstract

In contrast to the diffusion of membrane components in artificial lipid bilayers, diffusion in cells is both slower and non-ergodic. The physical origins of such anomalous diffusion are poorly understood, though cytoskeletal-membrane interactions and nanoscopic heterogeneity in the membrane have both been suggested to play an important role. There remains however a lack of controlled model systems on which to test these potential causes. Here we present a model system for reproducing this anomalous diffusion that utilizes supported lipid bilayers (SLBs) with varying degrees of excluded area fraction. By varying the concentration of PEG-lipids, we observe a dramatic and controllable switch in anomalous diffusion as we cross the estimated percolation threshold. This provides a simple model system for investigating this phenomenon in lipid membranes. The behavior is well described by both theory and Monte-Carlo simulation of the anomalous crossover as a function of obstacle density.