Berlin 2012 – wissenschaftliches Programm

Bereiche | Tage | Auswahl | Suche | Aktualisierungen | Downloads | Hilfe

BP: Fachverband Biologische Physik

BP 23: Cytoskeletal Filaments

BP 23.2: Vortrag

Donnerstag, 29. März 2012, 15:30–15:45, H 1028

Mechanical properties of actin bundles — •Florian Rückerl, Timo Betz, and Cécile Sykes — Institut Curie, Laboratoire P.C.C. (UMR168), Paris

Actin bundles can be used as simple models to understand the mechanical properties of filopodia. In our experiments the 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 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.

By attaching several beads to individual bundles we can create picoNewton forces in arbitrary directions. This allows the manipulation of individual bundles and, thereby, the investigation of their mechanical properties. These properties, mainly bending rigidity and viscoelasticity, are then probed by bending, pushing and pulling on the bundle.

Effects of different bundling mechanisms, e.g. by depletion forces induced by methyl cellulose (MC) or by crosslinkers like Fascin, as well as the influence of increased Mg²⁺ concentration are being investigated. Preliminary results show, that only low forces (≈8pN) are needed to bend the actin bundles formed by MC, while the elongation of these bundle requires much higher forces (>30pN). Elevated Mg²⁺ concentration (10mM) increases the force in both cases.