Diffusion limit on receptor-ligand association rates.

Page 240 of Fitting Models to Biological Data using Linear and Nonlinear Regresson states that association rate constants,  if dependent on diffusion, would be in the range of 10⁷ to 10⁸ M^-1 min^-1. In fact, the upper limit of diffusion has been estimated to much faster, about 10⁹ M^-1s^-1 (Burgen, 1966, J.Pharm. Pharmacol., 18:137). In fact, most drug-receptor pairs have slower association rates than that upper limit.