A simple and rapid orientation procedure for the estimation of affinities (1/Kd) and maximum binding capacities (Bmax) of ligand binding to two receptor subpopulations.

This paper describes a simple and rapid procedure for the estimation of specific parameters (dissociation constants, Kd and maximum binding capacities, Bmax) of ligand binding to two receptor subpopulations. This procedure provides, in a few minutes, the investigator, performing the actual binding studies, the necessary information about receptor heterogeneity, enabling the investigator to plan further experiments. The procedure is based on the graphical comparison of experimental binding data (ligand binding to one or two receptor subpopulations) with the theoretical values of ligand binding to one receptor population at four levels). The values of Kd and Bmax for high- and low-affinity receptors are derived from 4 horizontal deviations of experimental data from a theoretical data plot at these levels by their comparison with tabulated deviations. The correctness of the estimated parameters can be confirmed by the comparison of experimental data with those simulated on the basis of applying the values of Kd and Bmax found in the formula for ligand binding to two receptor subpopulations. The practical applicability of this procedure was demonstrated both on simulated and experimental data, and confirmed by the well known computer programs for evaluating receptor heterogeneity, namely "LIGAND" and "Affinity spectra".