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BP: Fachverband Biologische Physik

BP 10: Biofluiddynamics

BP 10.1: Hauptvortrag

Dienstag, 24. März 2009, 14:00–14:30, HÜL 186

Biohydrodynamics of biomimetic and bacterial flagella — •Holger Stark — Institut für Theoretische Physik, Technische Universität Berlin, Hardenbergstr. 36, D-10623 Berlin, Germany

At the micron scale fluid flow is in the low Reynolds number regime and nature had to be inventive to enable microorganisms to propel themselves in such an environment. Sperm cells, for example, use beating elastic filaments called flagella.

I shortly review our work on modeling a biomimetic flagellum consisting of superparamagnetic beads linked by DNA strands. Attached to a red-blood cell, the first artifical micro swimmer was created actuated by an oscillating magnetic field. The filament can also be attached to a surface in order to explore fluid transport for different beating patterns.

Many types of bacteria propel themselves with the help of a bundle of rotating helical flagella. These flagella can assume different types of helical conformations (polymorphism) depending on temperature, pH value of the solvent and applied external forces or torques as revealed by the tumbling motion of a bacterium. I will talk about our approach to model the flagellar polymorphism on the microscopic level of the flagellin proteins. Then, on a coarse-grained level I will discuss the hydrodynamics of a helical flagellum addressing explicitely the transition between two flagellar polymorphs observed when pulling at the flagellum. The analysis is performed on the basis of a generalized elasticity theory for a helical rod with two helical states. The influence of thermal noise and pulling speed on the force-extension curve is discussed.