Experiments on single-molecular energetics of biological molecular motor

A biological molecular motor is a nano-sized chemical engine that converts chemical free energy to mechanical motions. Hence, the elucidation of the energetics is of critical importance to understand its operation principle. We experimentally evaluated the thermodynamic properties of a rotational F₁-ATPase motor (F₁-motor) at a single-molecule level. For this purpose, we used nonequilibrium relations. We show that the F₁-motor achieves 100% thermodynamic efficiency at the stalled state. As well, the motor reduces the irreversible internal heat to almost zero during rotations far from a quasistatic process. We discuss F₁-motor's free-energy transduction mechanism, which highlights the remarkable property of the nano-sized engine F₁-motor. Furthermore, we found that the F₁-motor implements a rectification mechanism, which reduces futile energy consumption. The rectification mechanism is simple but circumvents the trade-off between the forward speed and forward/backward contrast suffered by a simple ratcheting mechanism. If time allows, I will also introduce our challenge to realize a synthetic molecular motor based on what we learned from the biological molecular motors. We are developing a DNA-origami-based motor with conformational change.