Specific features of kinetics of stochastically gated, diffusion-controlled reactions

The kinetics of diffusion-controlled, stochastically gated biochemical reac tions is analyzed within the markovian approximation for stochastic fluctua tions of reaction rate. With the use of methods developed in the theory of magnetic field effects on chemical reactions, several general expressions f or reaction rate and transient kinetics of geminate and bulk reactions are derived. In particular, it is shown that gating strongly manifests itself n ot only in steady-state reaction rates but also in the long time tail of ki netics. Specific features of gated reactions in the presence of attractive potential, resulting in the long-lived intermediate State: (cage), are disc ussed. Two simple markovian models of gating are considered which allow sig nificant simplification of the general expressions obtained. Within these m odels simple analytical formulas for reaction rate and reaction kinetics ar e derived and analyzed in detail.