The ionic strength dependence of the rate of a reaction between a small ion and a large ion with a dipole moment.

The ionic strength dependence of the rate constant of a reaction between a small ion and a large ion with a dipole moment (e.g. a protein) is described. This description takes into account only the electrostatic interactions between the two ions. This approach agrees with the Marcus theory treatment of the electrostatic interactions and also with the Debye-Hückel theory which is based on changes in the activity coefficients of the reactants. The contribution of the dipole moment of the protein to the ionic strength dependence of the rate constant has been calculated. A method is described whereby one can calculated the charge of the protein without knowing the precise ionic strength dependence of the rate constant. Two applications are mentioned to illustrate the usefulness of the method.