Diffusion-controlled reactions with a binding site hidden in a channel

The rate of a diffusion-controlled reaction with a buried binding site is smaller than the rate for the same site on the surface. We study the slowdown of the reaction rate when the site is hidden in a pore that connects two bulk media. On the assumption that the pore is cylindrical we derive an expression for the Laplace transform of the rate coefficient from which we infer the long-time limit of the reaction rate. This provides information on how the reaction rate depends on the channel radius, the location of the site, and the diffusion constant in the pore, which is allowed to differ from that in the bulk. The validity of approximations was checked by simulations that indicated excellent agreement between the analytical and and numerical results. (C) 2003 American Institute of Physics.