LIGAND-RECEPTOR BINDING IN THE PRESENCE OF A DIFFUSION GRADIENT.

Abstract

When, by means of surface receptors, a cell senses external levels of a chemical, the amount actually sensed can be strongly influenced by how fast the chemical diffuses away from (or towards) the cell. For a given binding affinity, the effect of diffusion becomes significant for small values of the , parameter ((12 k...1)/D) where / is of the order of the cell size, k..3 the dissociation rate of binding and D the diffusion coefficient of the chemical.