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BP: Fachverband Biologische Physik

BP 5: Posters: Biopolymers and Biomaterials

BP 5.37: Poster

Montag, 22. März 2010, 17:15–20:00, Poster B1

Testing the elastic anisotropy of microtubules by leveraged bending experiments — •Fabian Stiewe and Christoph F. Schmidt — Drittes Physikalisches Institut, Georg-August-Universität Göttingen

Microtubules are cylindrical protein shells with a distinct structural anisotropy, stemming from their construction from straight protofilaments that are connected more weakly laterally. This could lead to a length-dependence of the flexural rigidity and the persistence length of microtubules as reported recently. The effect is the stronger the "weaker" the connection between the protofilaments gets. We present here a method for sensitively testing this model. Two optical traps are used to suspend a microtubule with the help of two micron-sized beads. A force developed by pulling the traps apart leads to bending of the microtubule. A large difference between Young's and shear modulus should lead to a significant back-bending of the free ends of a bent microtubule, minimizing its free energy. We have used finite-element simulations to check the expected magnitude of this relaxation effect and compare the simulation results with data obtained in bending experiments using optical traps. To date we have not observed any back-bending in our experiments. Therefore we conclude that the difference in Young's and shear modulus might be too small to cause some of the reported effects.