Regensburg 2019 – scientific programme

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DY: Fachverband Dynamik und Statistische Physik

DY 60: Statistical Physics in Biological Systems III

DY 60.3: Talk

Friday, April 5, 2019, 10:30–10:45, H3

Force-dependent diffusion coefficient of molecular Brownian ratchets — •Matthias Uhl and Udo Seifert — II. Institut für Theoretische Physik, Universität Stuttgart, 70550 Stuttgart, Germany

We study the mean velocity and diffusion constant in models of molecular Brownian ratchets. Brownian ratchets can be used to describe translocation of biopolymers through nanopores in cells in the presence of molecules that prevent backwards transitions if bound to the polymer strand. We provide an analytical expression for the diffusion constant in the classical model of a translocation ratchet that was first proposed by Peskin et al. [1]. This model is only applicable if the binding and unbinding of the blocking molecules are much faster than the diffusion of the strand. We propose a modified model that is also applicable if the (un)binding rates are finite [2]. Our analysis shows that for large pulling forces the predictions of both models can differ strongly even if the (un)binding rates are large in comparison to the diffusion timescale but still finite. Implications of the thermodynamic uncertainty relation on the efficiency of Brownian ratchets are also discussed.

[1] C. S. Peskin, G. M. Odell, and G. F. Oster, Biophys. J. 65, 316 (1993).

[2] M. Uhl and U. Seifert, Phys. Rev. E 98, 022402 (2018).