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M: Metallphysik

M 13: Symposium Biomaterialien I

M 13.1: Talk

Tuesday, March 27, 2001, 10:15–10:45, S8

On Micromechanics of Cells — •Erich Sackmann — Physik Department E22, Lehrstuhl für Biophysik, TU München, James-Franck-Straße, D-85748 Garching

The central aim is to show that magnetic bead microrheology provides a valuable tool to measure local viscoelastic moduli of heterogeneous actin networks, cell envelope(s) and cytoskeletons and to measure local forces mediating intracellular trafficking. In the first part, correlations between phenomenological viscoelastic properties and single chain dynamics are summarized. One major purpose is to demonstrate that rheometry provides a valuable tool to explore the effects of actin regulation proteins on the single chain elasticity or dynamics and the structure of the networks. We then show that gradual cross-linking of entangled actin networks leads to a universal percolation transition into a microgel state (consisting of dense cross-linked clusters interconnected by few actin cables) which exhibit unique elastic and transport properties. The last part deals with the application of magnetic bead microrheometry

- as a viscoelastic microscope to measure local viscoelastic moduli of cell envelopes and cytoplasm(s) demonstrating that viscoelastic moduli are local quantities.

- as a colloidal force microscope allowing measurements of local forces during intracellular trafficking and

- as an analytical tool for real time studies of modifications of the membrane associated actin cortex by external signals.