Berlin 2008 – scientific programme

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BP: Fachverband Biologische Physik

BP 7: Posters I

BP 7.27: Poster

Monday, February 25, 2008, 17:00–19:30, Poster A

Superdiffusive motion with fractional power-law exponents in cytoskeleton-bound microbeads — •Max Sajitz-Hermstein, Claus Metzner, Raupach Carina, and Fabry Ben — Department Of Physics, University of Erlangen, Germany

The spontaneous random motion of microbeads bound to the cytoskeletal (CSK) network of living cells is a non-Brownian process [1]. The mean-squared-displacement (MSD) of the bead as a function of lag time shows a sub-to-superdiffusive transition that arises from the interplay of uncorrelated noise, dominating at short time scales, and persistent traction forces, dominating at longer times scales [2]. However, the fractional powerlaw exponent of the superdiffusive bead motion in the range from 1-2 is unexplained. We propose an analytical model for the CSK dynamics that accounts for superdiffusive behavior with fractional power-law exponents. The CSK is described as a network of elastic springs (stress fibers) undergoing gradual changes of rest length and stiffness due to ATP-driven processes. In addition, new fibers emerge spontaneously, generating an increasing and finally saturating prestress, which is coupled to the reinforcement of focal adhesions. The fiber growth is catalyzed by enzymes which constitute a limited, shared resource of the cell. We demonstrate that superdiffusion with a fractional powerlaw exponent arises naturally by a multiplicative noise process. Our model accounts quantitatively for the MSD data. [1] C. Raupach et al., Phys. Rev. E 76, 011918 (2007) [2] C. Metzner et al., Phys. Rev. E 76, 021925 (2007)