Condensed Matter journal club
Force-Velocity Measurements of a Few Growing Actin Filaments
- Event time: 11:30am
- Event date: 11th March 2011
- Speaker: Joe Tavacoli (Formerly School of Physics & Astronomy, University of Edinburgh)
- Location: Room 2511, James Clerk Maxwell Building (JCMB) James Clerk Maxwell Building Peter Guthrie Tait Road Edinburgh EH9 3FD GB
AbstractThe polymerization of actin in filaments generates forces that play a pivotal role in many cellular processes. We introduce a novel technique to determine the force-velocity relation when a few independent anchored filaments grow in the interspace between magnetic colloidal particles. Applying a magnetic field the colloidal particles assemble into chains under controlled loading or spacing. As the filaments elongate, the beads separate allowing the force-velocity curve to be precisely measured. In the acknowledged Brownian Ratchet model, the transduced force is associated to the slowing down of the on-rate polymerization. Unexpectedly, in our experiments, filaments are shown to grow at the same rate as when they are free in solution. However, as they elongate, filaments are more confined in the interspace between beads. Higher repulsive forces result from this higher confinement associated to a lower entropy. In this mechanism, the production of force is not controlled by the polymerization rate, but is a consequence of the restriction of filaments orientational fluctuations at their attachment point.
Coraline Brangbour, Olivia du Roure, Emmanuele Helfer, Damien Demoulin, Alexis Mazurier, Marc Fermigier, Marie-France Carlier, Jerome Bibette and Jean Baudry