Dresden 2009 – scientific programme
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BP: Fachverband Biologische Physik
BP 9: Actin Dynamics
BP 9.8: Talk
Tuesday, March 24, 2009, 12:45–13:00, ZEU 260
Force Generation of Expanding Actin Gels — •Stephan Schmidt1, Georg Freund2, Walter Zimmerman2, and Andreas Fery1 — 1Physikalsiche Chemie II, Universität Bayreuth,Universitätsstr. 30, 95440 Bayreuth Germany — 2Theoretische Physik I, Universität Bayreuth,Universitätsstr. 30, 95440 Bayreuth Germany
Force generation in actin gels is mainly associated with directed polymerization of actin monomers into branched filaments that extend against the load. Its ability to generate forces by monomer insertion is appealing from a material science point of view. However, while the biochemical processes associated with the actin polymerization are well understood, the molecular scale mechanism of force generation is still matter of debate. We use a simplified in vitro assay composed of purified proteins and artificial colloidal probes to directly study the forces during actin network growth. Force measurements on actin networks are performed using colloidal probe AFM techniques. In our setup the actin gel is compressed between a colloidal probe and a solid substrate while it deflects an AFM cantilever during expansion. Using fluorescence microscopy we observe the gel extension in direct conjunction with the AFM measurement. Furthermore, we vary the actin density and crosslinking via drugs or proteinic constituents like ARP2/3 and gelsolin. Generally, we observe increasing stall forces as the gel density or crosslinking density is increased. Results also suggest that the forces are limited by tensile stress build-up as the gel extends outward. Understanding of the gel behaviour in the framework of linear elasticity theory is subject to ongoing modeling efforts.