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BP: Fachverband Biologische Physik

BP 7: Fibers and Bundles

BP 7.3: Vortrag

Montag, 26. März 2007, 16:45–17:00, H44

Fluctuation Dynamics of Grafted Microtubules — •Francesco Pampaloni¹, Katja Taute², Gianluca Lattanzi³, and Ernst-Ludwig Florin² — ¹EMBL Heidelberg - Cell Biology and Biophysics Unit - Heidelberg, Germany — ²Center for Nonlinear Dynamics - University of Texas at Austin - Austin, USA — ³Department of Medical Biochemistry, Biology and Physics, University of Bari - Bari, Italy

Microtubules (MTs) are tubular protein filaments that constitute one of the main components of the cellular cytoskeleton. MTs are composed by a variable number of protofilaments (most frequently 13) made by the dimeric protein tubulin. MTs are highly optimized to a maximum of mechanical performance: the hollow cylindrical shape allows high strength and stiffness combined with a minimum of structural elements (tubulin dimers). Such features of MTs - light, flexible, and stiff at once - make them similar to versatile composite structures investigated by material scientists. Recent studies have shown that one key mechanical parameter, the persistence length, is subject to an unexpected dependence on the overall MT length. This has been attributed to the MT's large mechanical anisotropy on the molecular level. We performed a dynamical analysis of the thermal fluctuations of grafted MTs obtaining first mode relaxation times. Single-particle tracking was employed to measure the fluctuations of the free end of the filament. We found that relaxation times follow an L^2 instead of an L^4 dependence for short microtubules. This relation is shown to result from the length dependence of the persistence length.