Berlin 2008 – scientific programme

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BP: Fachverband Biologische Physik

BP 19: Semiflexible Polymers and Networks

BP 19.2: Talk

Wednesday, February 27, 2008, 17:45–18:00, PC 203

A Stiff Rod in Dense Environments: A Paradigm for Translation--Rotation Coupling — •Tobias Munk, Felix Höfling, Erwin Frey, and Thomas Franosch — Arnold Sommerfeld Center and CeNS, Ludwig-Maximilians-Universität München, Germany

Everybody who once observed a long lorry trying to turn in a small street knows of the consequences of the coupling of translational and rotational motion in the macroscopic world. On the micro scale, similar things happen to anisotropic objects diffusing in a crowded environment. This is found for example in biological cells: their interior is enormously crowded by huge amounts of proteins and other complexes, thus diffusing anisotropic objects are largely constricted by their surroundings. This happens e.g. to free actin filaments moving in the cytoskeleton.

We have set up a simple two-dimensional model in order to examine the Brownian motion of a stiff rod in a sterically hindered medium on all physically relevant timescales. A theoretical description of the unobstructed motion is developed by mapping the corresponding anisotropic diffusion equation to the Smoluchowski-equation. This, however, is not sufficient to grasp the translation--rotation coupling induced by the obstacles. By means of molecular dynamics simulations we point on these coupling effects and demonstrate that the motion is non-gaussian at intermediate times.