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Deciphering Actin networks mechanics by a new high-throughput experiment

Lundi 8 avril 2013 14:00 - Duree : 1 heure
Lieu : Laboratoire Interdisciplinaire de Physique (ex LSP), Salle 216 Bât. E - 140 Avenue de la Physique Domaine Universitaire - St-Martin-d’Hères

Orateur : Olivia DU ROURE (Physique et Mécanique des Milieux Hétérogènes, PMMH, Paris)

Actin networks are of paramount importance for cellular mechanics as they ensure cell integrity, deformability and migration. The relationship between the properties of the actin filaments, their associated proteins and the mechanics of the different organizations of the cytoskeleton remains elusive. Mechanics of actin networks has been studied so far with classical macro/micro rheometry at low actin concentration, or with demanding techniques such as atomic force microscopy at more physiological concentrations. We have developed a new method of mechanical measurement, based on the dipolar attraction between magnetic colloids. This technique allows us to probe thousands of gels, orders of magnitude more than previous experiments. We have first focused on dense branched networks assembled by the Arp2/3 complex in a minimum mix of purified proteins. By changing the proportion of nucleators or regulatory proteins, we have measured a strong dependence of the elasticity on the architecture of the networks. The internal stress in the actin gel has a small impact on the elasticity on the networks, in contrast to low concentration gels studied with rheometry. Our results are more in agreement with an elasticity that comes from the rigid fibers’ bending and stretching than from semi-flexible polymers’ entropic stretching in such dense branched actin networks. I will also show some preliminary results obtained in collaboration with Alphee Michelot and Laurent Blanchoin on branched actin networks assembled from yeast extract. On the experimental point of view, I will also present a new development using magnetic particles of controlled shapes (cubes, disks...). This will allow the dipolar magnetic technique to be used for a greater number of applications, including dynamic measurements on growing actin gels and the direct measurement of adherent cells mechanical properties with a great throughput.

Contact : sigolene.lecuyer@ujf-grenoble.fr

Discipline évènement : (Physique)
Entité organisatrice : (LIPhy)
Nature évènement : (Séminaire)
Evènement répétitif : (Séminaire Mat. Molle/grise)
Site de l'évènement : Domaine Universitaire de St Martin d’Hères

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