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Poster, Friday, 19:00  
Formation of regular actin networks as general feature of entropic forces

Florian Huber, Dan Strehle, Jörg Schnauß, Matti Gralka, Josef A. Käs

University of Leipzig, Faculty of Physics and Earth Sciences, Institute of Experimental Physics I, Soft Matter Physics Division, Linnéstraße 5, 04103 Leipzig, Germany
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Biopolymer networks contribute mechanical integrity as well as functional organization to living cells. The protein actin is one of the major constituents of those structures and was found to be present in a large variety of different network architectures ranging from extensive networks to densely packed bundles or fibers. Although the network shape will dramatically influence the macroscopic mechanical properties as well as essential cytoskeletal functions, we still possess only a fairly limited understanding of architecture determining mechanisms.
We developed a reduced experimental bottom-up system to study the formation of confined actin networks by entropic forces. Experiments based on molecular crowding or counterion condensation reveal a very general tendency of homogeneous filament solutions to aggregate into regular actin bundle networks connected by aster-like centers. Drastic changes in network architecture directly follow from filament ordering or from flow-induced perturbations of the system. Complementing the experimental data we aim at further explaining the results consistently on the basis of coarse-grained modeling. 
Experiments and theory suggest that the tendency to form regular bundle networks is a rather general feature of isotropic, homogeneous filament solutions subject to uniform attractive interactions. Due to the fundamental nature of the interactions considered, we expect that the investigated type of network formation further implies severe consequences or restrictions to cytoskeletal network formation on the more complex level of living cells.
University of Leipzig  |  Faculty of Physics and Earth Sciences  |  Institute of Experimental Physics I  |  Soft Matter Physics Division
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