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BP: Fachverband Biologische Physik

BP 21: Biopolymers and Biomaterials II (with CPP)

BP 21.5: Vortrag

Mittwoch, 16. März 2011, 11:45–12:00, ZEU 260

Dynamics and mechanics of formin mediated actin bundles — •Florian Rückerl, Timo Betz, and Cécile Sykes — UMR168, Institut Curie, Paris

In our experiments actin filaments and actin bundles are produced by polymerization by the formin mDia1(FH1FH2). To probe their dynamics and mechanics, we use a state of the art optical tweezers setup and create multiple traps (2 to 5) with acousto-optical deflectors (AODs). Digitally controlled AODs in time sharing mode allow to position and move several traps simultaneously. Employing a four quadrant diode as a position detector results in high temporal and spatial resolution, 10µs and <1nm, respectively. This allows to investigate the polymerizing dynamics of mDia1 by directly observing the deflection of formin coated beads inside the optical trap. Preliminary results indicate single monomer addition events at infrequent intervals.

By attaching several beads to individual bundles we can create pico-Newton forces in arbitrary directions. The mechanical properties of the bundle are then probed by bending, pushing and pulling on the bundle. We find that pulling on a bundle leads to its elongation, presumably by relative sliding of the bundle filaments to each other.

Furthermore, the setup can be used for the direct manipulation of the bundles without beads attached to it, allowing for an in situ non invasive measurement. Correlating the local fluctuations at several positions on the bundle yields its persistence length and gives an estimate of the number of filaments in the bundle.