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PV: Plenarvorträge

PV XV

PV XV: Plenarvortrag

Freitag, 30. März 2007, 08:30–09:15, H1

Active gels: toward a generic approach of cell mechanics — •Jean-François Joanny — Physicochimie Curie (CNRS-UMR168), Institut Curie Section Recherche, 26 rue d'Ulm, 75248 Paris Cedex 05, France

Active systems are systems where energy is constantly injected by a chemical reaction or by an external drive. Examples of active systems are vibrated sand piles, bird flocks or fish colonies. The cell cytoskeleton is also active : the energy is provided by the hydrolysis of ATP molecules which both promotes the polymerization and the depolymerization of the cytoskeletal filaments but also is used as a fuel by the molecular motors that walk along the filaments and create internal stresses. The dynamical properties of the cytoskeleton seem to be dominated by the gel formed by actin filaments interacting with myosin motors. A further property of the cytoskeletal filament is their polarity which imposes a local orientation in the gel.

We have built a general hydrodynamic theory to describe the rheology of polar active gels in the spirit of the hydrodynamic theory of liquid crystals. The theory takes into account the viscoelasticity of the gel, the polymerization and depolymerization, the local polarization, and the active stresses induced in the gel. We briefly present this theory and show some very unusual hydrodynamic behavior of active gels that can flow spontaneously even in the absence of any pressure gradient. We then give some examples of application of active gel hydrodynamics to study the properties of cells: lamellipodium motion, cell instabilities driven by cortical actin.

This work has been done in collaboration with F. Jülicher, K. Kruse, J. Prost and K. Sekimoto.