Efficiency of isothermal molecular machines at maximum power
  We derive upper and lower bounds for the efficiency of an isothermal molecular machine operating at maximum power. The upper bound is reached when the activated state is close to the fueling or reactant state (Eyring-like), while the lower bound is reached when the activated state is close to the product state (Kramers-like). 
Christian Van den Broeck, Niraj Kumar and Katja Lindenberg
cond-mat.stat-mech cond-mat.soft physics.bio-ph