Relaxation kinetics of ion binding

Abstract

The following expression is derived for the relaxation time τ associated with an ion binding equilibrium: [graphic omitted] (I) where r denotes the equilibrium forward or backward rate and where C₁, C_p, m₁ and C₃, respectively, denote concentrations (mol per unit mass of solvent) of solute, 1, substrate, p, unbound solute and supporting electrolyte, 3. Species 1 and 3 have the same valency and a common counterion (2). The only assumption made to obtain eqn (I) is that the activity coefficients of unbound solute and species 3 are equal. The derivatives in eqn (I) can be obtained from equilibrium binding studies, and the treatment does not depend on any particular model for the binding process. Eqn (I) is shown to be entirely consistent with one such model for surfactant ion binding to macromolecules.