Control of chemical equilibrium by noise

We formulate a theory of reactive transport in the presence of environmental fluctuations that restart a transfer attempt, such as, for instance, during charge transfer through an intermediate state on a fluctuating bridge. It is shown that the rate and statistics of the fluctuations affect the steady-state populations of the reactants and products and the rate at which the steady state is approached. We give explicit examples in which the reactant/product populations can be inverted by varying the rate of environmental fluctuations. We thus propose a design principle of a controllable molecular scale device. We speculate that when noise-controlled charge transfer takes place in nature, as during electron transport in bacterial photosynthetic reaction centers, such a design can be used to maintain functionality over a wide temperature range and would be favored by evolution.