Many biologically relevant reactions are gated: i.e., the reaction A* + B -> C is modulated by an interconversion A* <-> A, where the state A is inactive and does not react with B. A blocker D can cause the interconversion: A* + D <-> A. It is possible to solve for (the Laplace transform of) the rate coefficient for many types of gating in terms of its counterpart for the ungated reactions. General Green's function and trapping rate identities avoid a diffusion-based formulation and permit a general approach to gating through standard Laplace transform identities. The quantities with and without gating are then related through conservation equations to solve the mathematical problem. Under standard experimental conditions, with a blocker in excess (e.g., a viral blocker like an antibody), blocking is equivalent to gating. In practice, the blocker's equilibrium constant in the gating reaction (e.g., antibody association constant) is often taken as a surrogate for its biological activity. The gating solutions clearly show, however, that the on- and off-rates themselves (and not just their ratio, the equilibrium constant) have an influence on the blocker's effectiveness.
