On diffusion-limited site-specific association processes for spherical and nonspherical molecules

A detailed analysis is presented of the translational and rotational transport processes underlying site-specific binding of a diffusing solute with a fixed target molecule. The need for contact to occur between localized active centers is modelled using a position- and orientation-dependent catalytic rate coefficient peaked about a maximum value at the preferred lock-and-key contact configuration. Numerical calculations are effected in part via application of perturbation methods to the general transport theory. They show the effects upon the observed association rate of molecular size, degree of chemical specificity, nonspherical reactant shape, nonspecific and site-specific intermolecular forces, and hydrodynamic interaction. Realistic representation of enzymes is addressed briefly with reference to a trypsin-catalyzed reaction.