Stochastic modeling of protein motions within cell membranes.

A simple model in which immobilizing events are imposed onto otherwise free Brownian diffusion [R. Metzler and J. Klafter, Phys. Rep. 339, 1 (2000) and a recent adaptation due to S. Khan and A. M. Reynolds, Physica A 350, 183 (2005)] is shown to encapsulate the peculiar transport characteristics of individual cell receptors within plasma membranes observed in single-particle tracking (SPT) experiments. These characteristics include the occurrence of normal diffusion; non-Gaussian subdiffusion; confined diffusion; a superdiffusive mode of transport that is not due to flow of the membrane or molecular motor attachment; and the occurrence of transitions between these transport modes. Model predictions are shown to be in close agreement with a reanalysis of existing SPT data.