Quantifying the Heat Dissipation from a Molecular Motor's Transport Properties in Nonequilibrium Steady States

TL;DR

This paper provides a theoretical framework to quantify heat dissipation in molecular motors and explains how their transport properties, like velocity and diffusivity, are interconnected in nonequilibrium steady states, highlighting the efficiency of kinesin-1.

Contribution

It introduces a unicyclic Markov process model to evaluate heat dissipation and elucidates the relationship between heat, velocity, and diffusivity in molecular motors.

Findings

Diffusivity increases with heat production in active particles.

Kinesin-1 efficiently converts conformational fluctuations into directed motion.

Heat enhances self-diffusion of exothermic enzymes, explained through thermodynamics.

Abstract

Theoretical analysis, which maps single molecule time trajectories of a molecular motor onto unicyclic Markov processes, allows us to evaluate the heat dissipated from the motor and to elucidate its dependence on the mean velocity and diffusivity. Unlike passive Brownian particles in equilibrium, the velocity and diffusion constant of molecular motors are closely inter-related to each other. In particular, our study makes it clear that the increase of diffusivity with the heat production is a natural outcome of active particles, which is reminiscent of the recent experimental premise that the diffusion of an exothermic enzyme is enhanced by the heat released from its own catalytic turnover. Compared with freely diffusing exothermic enzymes, kinesin-1 whose dynamics is confined on one-dimensional tracks is highly efficient in transforming conformational fluctuations into a locally directed motion, thus displaying a significantly higher enhancement in diffusivity with its turnover rate. Putting molecular motors and freely diffusing enzymes on an equal footing, our study offers thermodynamic basis to understand the heat enhanced self-diffusion of exothermic enzymes.