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AKB: Biologische Physik

AKB 100: Poster Session I

AKB 100.77: Poster

Samstag, 5. März 2005, 16:45–18:45, Poster TU D

Active vs. Passive Microrheology — •Daisuke Mizuno, Frederick C. MacKintosh, and Christoph F. Schmidt — Dept. Physics, Vrije Universiteit, Amsterdam, NL

We have performed passive and active 2-particle microrheology (MR) in actin solutions by using the same micron-sized colloidal particles as a probes. In passive MR, viscoelasticity is measured from the correlated thermal fluctuations of the probe particles. In active MR, one probe particle is sinusoidally driven by an oscillating optical trap while the correlated motion of the other one is detected by laser interferometry. In equilibrium, both methods give the same results. In non-equilibrium, however, such as in living cells, random, nonthermal stress fluctuations prevent the use of the fluctuation-dissipation theorem. Probe motions are influenced by e.g. the activity of motor proteins or directional polymerization/depolymerization of actin and microtubules. Active components also modify the viscoelastic response of the cytoplasm. The main aim of our research is to gain a better understanding of microscopic dynamics in such non-equilibrium systems by combining active and passive microrheology.