Relaxation Spectroscopy Applied to Determination of Rate Constants for Ligand Binding and Dissociation

Abstract

Application of relaxation methods for determining individual rate constants for ligand binding to a receptor is presented. The method requires that a ligand is available which has a spectroscopic property that changes upon binding to the receptor. The rate constants for binding (k₂) and dissociation (k_-2) for such a “labelled” ligand (Y) can be determined using conventional relaxation methods (3). The purpose of the present paper is to show that kinetic parameters k₁ and k_-1 for an unlabelled ligand (X) also can be determined, using the influence of the unlabelled ligand on the binding of the labelled ligand to the receptor (R).