Diffusion-controlled reaction rates for clusters of binding sites on a cell

Abstract

The Berg-Purcell expression for the diffusion-controlled binding rate to N sites uniformly distributed on the surface of a sphere is generalized to clusters of receptors located at the poles of a cell. By replacing a partially reactive surface with one that is covered with N circular sites that act independently, one can derive analytic expressions for the diffusion-controlled rate constant for clusters of binding sites. This has application to systems where the reactive sites are located in a specific region or regions on the surface of the protein or cell. These include peptide hormones reacting with target receptors, protein-ligand reactions and bacterial chemotaxis. Multiple sensory receptors both at one and two poles of a sphere are studied.

Keywords

• diffusion-controlled; ligand binding; binding site; receptor clusters; cell kinetics