Molecular motor efficiency is maximized in the presence of both power-stroke and rectification

Abstract

We present a model for a feedback-controlled ratchet consisting of a Brownian particle and a moving, finite barrier that is shifted by an external agent depending on the position of the particle. By modifying the value of a single parameter of the feedback protocol, the model can act either as a pure rectifier, a power-stroke (PS) motor, or a combination of both. Interestingly, in certain situations the motor reaches a maximum efficiency for an intermediate value of that parameter, i.e., for a combination of the information ratchet and the PS mechanisms. We relate our results to the biological motors kinesin, myosin II, and myosin V, finding that these motors operate in a regime of length scales and forces where the efficiency is maximized for a combination of rectification and PS mechanisms.