  We propose a dynamic mechanism of a molecular machine for energy conversion,
by considering a simple model describing the dynamics of two components, the
head and the chain. After injection of energy to the head region, the energy is
stored at one part for some time, and is used step by step, allowing the head
to move directionally along the chain, irrespectively of the direction of the
input, under a fluctuating environment. Our system can adjust the timing with
which the head crosses the energy barrier by taking advantage of internal
dynamics and the flexibility of components. The mechanism is shown to be robust
and efficient. Some suggestions are given for molecular machines.
