Efficient experimental driving of a molecular machine

Molecular machines are central actors in essentially all biological processes. F1 ATPase is one of the most studied molecular machines and is a core component of cellular energy transduction across all forms of life. In vivo, F1 converts rotation of a molecular crankshaft (driven by its partner machine, Fo) into free energy in the form of ATP. This energy conversion can be remarkably efficient, raising interest in understanding the mechanisms by which such machines can faithfully transduce energy despite their large stochastic fluctuations. Here we compare the experimental efficiency of two qualitatively distinct driving modes of a single F1 molecule: applying a constant torque and rotating at a constant rate. Supported by simple theory and simulation, we identify design principles governing the efficient nonequilibrium driving of F1, and by implication other molecular machines.