Dresden 2009 – scientific programme

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BP: Fachverband Biologische Physik

BP 9: Actin Dynamics

BP 9.3: Talk

Tuesday, March 24, 2009, 11:15–11:30, ZEU 260

Quantifying athermal fluctuations in active actomyosin complexes — •David Head¹ and Daisuke Mizuno² — ¹IFF Theorie II, Forschungszentrum Jülich, GERMANY — ²Organization for the Promotion of Advanced Research, Kyushu University, Fukuoka, JAPAN

Active gels represent a class of non-equilibrium materials that are currently undergoing vigourous research due to their relevance to a range of important biomechanical processes. The motility, structural and mechanical properties of eukaryotic cells are determined in part by the interaction between protein filaments and motor proteins activated by a reservoir of energy transfer molecules such as ATP. Being athermal in origin, the pN-scale force impulses generated by motor activations violate the fluctuation-dissipation theorem, and first principles modeling is required to relate microscopic processes to macroscopically measurable quantities. Here we present the results of such calculations based on the two-fluid model, in which the active agents are spatially uncorrelated but their stress fields decay algebraically, generating long-range correlations that can and have been measured in 2-particle microrheology experiments. 1-particle results are also derived, and both sets of calculations are supported by zero-frequency elasticity calculations performed in real space. Beyond the obvious advantages of allowing direct comparison to experiment, these results can also be used to speculate about the early-time instability of isotropic networks in the absence of permanent crosslinks, leading to the well-known phenomenon of super-precipitation.