Insights from an information thermodynamics analysis of a synthetic molecular motor

We analyze a minimalist experimental example of an autonomous artificial chemically-driven molecular motor - a molecular information ratchet - in terms of information thermodynamics. This treatment reveals how directional motion is generated by free energy transfer from the chemical to the mechanical processes involving the motor. We identify the efficiency with which the chemical fuel powers the free energy transfer and show that this is a useful quantity with which to compare and evaluate mechanisms of, and guide designs for, molecular machines. The study provides a thermodynamic level of understanding of molecular motors that is general, complements previous analyses based on kinetics, and has practical implications for designing and improving synthetic molecular machines, regardless of the particular type of machine or chemical structure. In particular, we find that under some conditions power strokes can modulate the molecular motor current (how fast the components rotate), efficiency with respect to how free energy is dissipated, and the number of fuel molecules consumed per cycle. This may help explain the role of such conformational changes in biomolecular machine mechanisms and illustrates the interplay between energy and information in chemical systems.