Regensburg 2007 – scientific programme

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BP: Fachverband Biologische Physik

BP 15: Biopolymer Solutions and Networks

BP 15.8: Talk

Tuesday, March 27, 2007, 17:00–17:15, H44

Modelling Non-Brownian Fluctuations in Stress Fiber Networks — •Claus Metzner, Carina Raupach, Daniel Paranhos-Zitterbart, and Ben Fabry — Biophysics Group, University of Erlangen, Germany

Microbeads attached to the intracellular actomyosin network show spontaneous fluctuations of non-thermal origin. Their motion is characterized by a transition from sub- to superdiffusive mean square displacement (MSD) with increasing lag time. This signature, associated with qualitative changes of the turning angle distribution, is reminescent of a particle diffusing in a potential well with slowly drifting minimum position. By solving this drifting well model analytically, we show that the complex statistical properties of the observed bead trajectories are captured by a small number of parameters.

Next we demonstrate numerically that a dynamic stress fiber network is a biologically plausible realization of drifting well behaviour. Essential features of the network include the formation of new fibers by actin polymerization, the building up of prestress by myosin crossbridges, the elastic properties of the established fibers, and the reverse processes of fiber degradation. Here, noise caused by myosin activity represents the non-thermal driving force of the diffusion. Established fibers, adhering to the bead surface and connecting radially to the remaining network, form an elastic cage and create a plateau in the MSD. The occasional formation or degradation of bead-linked fibers gives rise to superdiffusive and directed motion on longer time scales.