Pendulum as a model system for driven rotation in molecular nanoscale machines

We suggest a ratchet mechanism of rotatory (or translatory) motion of a Bro wnian rotator (or a particle) in a spatially symmetric periodic potential. The asymmetry that drives the ratchet motion is due to a special sequence o f activation of catalytic sites arranged in space circularly and periodical ly. A pendulum driven by short impulses at its stable equilibrium point is shown to be a simple mechanical model which can be constructed easily and u sed for visual observation of the ratchet rotation. A possible application of this mechanism in nanotechnology is briefly discussed.