Berlin 2005 – wissenschaftliches Programm

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CPP: Chemische Physik und Polymerphysik

CPP 7: SYMPOSIUM: Polymer networks and beyond: From molecular structure to materials and biological functions II

CPP 7.4: Vortrag

Samstag, 5. März 2005, 12:00–12:15, TU C243

MICRORHEOLOGY OF GEOMETRICALLY CONFINED ACTIN NETWORKS — •Mireille Claessens, Rainer Tharmann, Bernd Wagner, and Andreas Bausch — TUM Physik Department E22, James Franck Straße, D-85747 Garching

The semiflexible polymer actin is one of the mayor components of the cytoskeleton and plays an important role in the mechanical properties of cells. There are several studies concentrating on the rheology of actin and other cytoskeletal polymer networks. Here we address the important aspect of the geometrical confinement imposed by the plasma membrane on the network dynamics.

We confined the actin network into the water droplets of a water-in-dodecane emulsion. To mimic the presence of the plasma membrane the droplets were stabilized with a monolayer of negatively charged phospholipids. The mean length of the actin filaments was controlled by polymerizing in the presence of gelsolin. The effect of the spherical confinement on the viscoelastic properties of entangled actin networks was studied using microrheometry. In large emulsion droplets the plateau modulus G₀ of the confined actin network was comparable to the modulus found in bulk measurements. For networks of filaments shorter than the persistence length, G₀ was found to be independent of the droplet diameter, D. However when the filaments were longer than the persistence length G₀ was observed to increase with decreasing droplet diameter. The increase scaled as D⁻³ which suggest that the presence of the droplet wall hinders rapid relaxation of tension to the ends of the chain.