Kinesin and the Crooks fluctuation theorem

TL;DR

This paper investigates the thermal efficiency of kinesin motors at stalling, clarifies conflicting predictions, and establishes an upper bound on efficiency using the Crooks fluctuation theorem, confirming the second law of thermodynamics.

Contribution

It introduces an ideal kinesin cycle model to compare with real cycles, applying the Crooks fluctuation theorem to analyze efficiency bounds.

Findings

Real kinesin efficiency is always less than the ideal cycle.

The ideal kinesin cycle has a thermal efficiency below 100%.

The analysis confirms the second law of thermodynamics for kinesin motors.

Abstract

The thermal efficiency of the kinesin cycle at stalling is presently a matter of some debate, with published predictions ranging from 0 (A. W. C. Lau, D. Lacoste and K. Mallick, Phys. Rev. Lett. 99, 158102 (2007); D. Lacoste, A. W. C. Lau and K. Mallick, Phys. Rev. E78, 011915 (2008)) to 100% (G. Oster and H. Wang, in Molecular Motors, edited by M. Schliwa (Wiley-VCH Verlag GmbH, Weinheim (2003), p. 207). In this note we attemp to clarify the issues involved. We also find an upper bound on the kinesin efficieny by constructing an ideal kinesin cycle to which the real cycle may be compared. The ideal cycle has a thermal efficiency of less than one, and the real one is less efficient than the ideal one always, in compliance with Carnot's theorem.