Brownian Dynamics of Viscoelastic Materials

A unifying theoretical framework for analyzing stochastic data from single-particle tracking (SPT) in viscoelastic materials is presented. A generalization of the bead-spring model for linear polymers is developed from a molecular point of view and from the standpoint of phenomenological linear viscoelasticity. The hydrodynamic interaction in the former is identiied as the dashpots in the latter. In elementary terms, the intimate correspondence between time-correlation of the uctuation measurements and transient relaxation kinetics after perturbation is discussed, and the central role of uctuation-dissipation relation is emphasized. The work presented here provides a bridge between the microscopic and the macroscopic views of linear viscoelastic biological materials, and is applicable to membrane protein diiusion, linear DNA chain dynamics, as well as mechanics of intracellular cytoskeletal networks. Running title: SPT Study of Viscoelasticity Keywords: Bead-and-spring/ creep function/ uctuation-dissipation/ macromolec-ular mechanics/ nano-biochemistry/ video-enhanced optical microscopy 1 INTRODUCTION