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AKB: Biologische Physik

AKB 25: Cell Mechanics I

AKB 25.2: Talk

Thursday, March 30, 2006, 15:15–15:30, ZEU 260

Phase behaviour and micro-mechanical properties of crosslinked actin-networks — •Oliver Lieleg and Andreas R. Bausch — Lehrstuhl für Biophysik E22, Physik-Department, Technische Universität München, D-85747 Garching, Deutschland

Cell shape, mechanics and motility are mainly determined by crosslinked actin-networks. Despite their importance, the mechanical function of crosslinking molecules is not well understood. As in living cells many different actin crosslinking molecules are used simultaneously, it is necessary to study their effect in in vitro systems. Here two structural related crosslinking molecules are compared: α-actinin and I-plastin. Their effect on the structure and mechanics of in vitro actin networks is investigated. Actin networks crosslinked by α-actinin or I-plastin show pronounced differences in their elastic properties as a function of the crosslinker-to-actin-ratio. Interestingly, these differences are observed although both crosslinking molecules use the same calmodulin-homologous domain for actin binding. For both systems at least three distinct phases of actin-networks with different viscoelastic properties are observed. By rheological and optical methods these are related to the microscopic structure of the networks. The occurrence of mixed networks containing bundles embedded in an isotropic network indicates that a sharp distinction between crosslinking and bundling proteins might be artificial and multiple phases could also be possible for other actin-crosslinking proteins.