title: Analysis of molecular diffusion by first-passage time variance identifies the size of confinement zones.
abstract: The diffusion of receptors within the two-dimensional environment of the plasma membrane is a complex process. Although certain components diffuse according to a random walk model (Brownian diffusion), an overwhelming body of work has found that membrane diffusion is nonideal (anomalous diffusion). One of the most powerful methods for studying membrane diffusion is single particle tracking (SPT), which records the trajectory of a label attached to a membrane component of interest. One of the outstanding problems in SPT is the analysis of data to identify the presence of heterogeneity. We have adapted a first-passage time (FPT) algorithm, originally developed for the interpretation of animal movement, for the analysis of SPT data. We discuss the general application of the FPT analysis to molecular diffusion, and use simulations to test the method against data containing known regions of confinement. We conclude that FPT can be used to identify the presence and size of confinement within trajectories of the receptor LFA-1, and these results are consistent with previous reports on the size of LFA-1 clusters. The analysis of trajectory data for cell surface receptors by FPT provides a robust method to determine the presence and size of confined regions of diffusion.
authors.affiliation: Department of Mathematical and Statistical Sciences, University of Alberta, Edmonton, Alberta, Canada.
authors.forename: Vishaal
authors.initials: V
authors.lastname: Rajani
authors.forename: Gustavo
authors.initials: G
authors.lastname: Carrero
authors.forename: David E
authors.initials: DE
authors.lastname: Golan
authors.forename: Gerda
authors.initials: G
authors.lastname: de Vries
authors.forename: Christopher W
authors.initials: CW
authors.lastname: Cairo
mesh_terms: D002462:Cell Membrane / Q000378:metabolism; D004058:Diffusion; D016169:Lymphocyte Function-Associated Antigen-1 / Q000378:metabolism; D008954:Models, Biological; D013269:Stochastic Processes; D013997:Time Factors
chemical_list: D016169:Lymphocyte Function-Associated Antigen-1