title: Distribution of directional change as a signature of complex dynamics.
abstract: Analyses of random walks traditionally use the mean square displacement (MSD) as an order parameter characterizing dynamics. We show that the distribution of relative angles of motion between successive time intervals of random walks in two or more dimensions provides information about stochastic processes beyond the MSD. We illustrate the behavior of this measure for common models and apply it to experimental particle tracking data. For a colloidal system, the distribution of relative angles reports sensitively on caging as the density varies. For transport mediated by molecular motors on filament networks in vitro and in vivo, we discover self-similar properties that cannot be described by existing models and discuss possible scenarios that can lead to the elucidated statistical features.
authors.affiliation: James Franck Institute, Department of Chemistry, Institute for Biophysical Dynamics, Department of Medicine, and Department of Physics, University of Chicago, Chicago, IL 60637.
authors.forename: Stanislav
authors.initials: S
authors.lastname: Burov
authors.forename: S M Ali
authors.initials: SM
authors.lastname: Tabei
authors.forename: Toan
authors.initials: T
authors.lastname: Huynh
authors.forename: Michael P
authors.initials: MP
authors.lastname: Murrell
authors.forename: Louis H
authors.initials: LH
authors.lastname: Philipson
authors.forename: Stuart A
authors.initials: SA
authors.lastname: Rice
authors.forename: Margaret L
authors.initials: ML
authors.lastname: Gardel
authors.forename: Norbert F
authors.initials: NF
authors.lastname: Scherer
authors.forename: Aaron R
authors.initials: AR
authors.lastname: Dinner
mesh_terms: D008841:Actin Cytoskeleton / Q000737:chemistry; D003102:Colloids / Q000737:chemistry; D003627:Data Interpretation, Statistical; D008962:Models, Theoretical; D009038:Motion; D013269:Stochastic Processes
chemical_list: D003102:Colloids
keywords: angular correlation; cytoskeleton; random walks