Efficiently driving F₁ molecular motor in experiment by suppressing nonequilibrium variation

F₁-ATPase (F₁) is central to cellular energy transduction. Forcibly rotated by another motor Fₒ, F₁ catalyzes ATP synthesis by converting mechanical work into chemical free energy stored in the molecule ATP. The details of how Fₒ drives F₁ are not fully understood; however, evaluating efficient ways to rotate F₁ could provide fruitful insights into this driving since there is a selective pressure to improve efficiency. Here, we show that rotating F₁ with an angle clamp is significantly more efficient than a constant torque. Our experiments, combined with theory and simulation, indicate that the angle clamp significantly suppresses the nonequilibrium variation that contributes to the futile dissipation of input work.