Efficiency of molecular machines with continuous phase space

¹ Department of Physics and Astronomy, University of Aarhus - Ny Munkegade, Building 1520, DK-8000 Aarhus C, Denmark, EU
² Dipartimento di Scienze Fisiche and Sezione INFN, Università “Federico II” - Complesso Monte S. Angelo, I-80126 Napoli, Italy, EU

^a imparato@phys.au.dk

Received: 26 January 2012
Accepted: 27 February 2012

Abstract

We consider a molecular machine described as a Brownian particle diffusing in a tilted periodic potential. We evaluate the absorbed and released power of the machine as a function of the applied molecular and chemical forces, by using the fact that the times for completing a cycle in the forward and the backward direction have the same distribution, and that the ratio of the corresponding splitting probabilities can be simply expressed as a function of the applied force. We explicitly evaluate the efficiency at maximum power for a simple sawtooth potential. We also obtain the efficiency at maximum power for a broad class of 2-D models of a Brownian machine and find that loosely coupled machines operate with a smaller efficiency at maximum power than their strongly coupled counterparts.