Berlin 2008 – wissenschaftliches Programm

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BP: Fachverband Biologische Physik

BP 12: Cellular Force Generation

BP 12.2: Vortrag

Dienstag, 26. Februar 2008, 17:45–18:00, C 243

Efficiency of molecular motors at maximum power: “Power stroke” beats “Brownian ratchet” — •Tim Schmiedl and Udo Seifert — II. Institut für Theoretische Physik, Universität Stuttgart, 70550 Stuttgart

Molecular motors transduce chemical energy from hydrolizing ATP into mechanical work exerted against an external force. The efficiency of such a motor usually increases when increasing the force, reaching the maximum at the stall force. At this force, however, the velocity of the molecular motor and the power output vanishes. It is thus more meaningful to characterize such motors by the efficiency at maximum power. We calculate this efficiency for a simple model and show that the qualitative behaviour depends crucially on the position of the transition state or, equivalently, on whether the motor step occurs in a so called “power stroke” or in a “Brownian ratchet” manner. Specifically, we find a power stroke mechanism, as realized e.g. in myosin motors, to be most favourable with respect to both high power output and high efficiency at maximum power. In this regime, driving the motor farther out of equilibrium by applying higher chemical potential differences can, contra-intuitively, increase the efficiency.