Saturation radioligand binding experiments measure specific radioligand binding at equilibrium at various concentrations of the radioligand. Analyze these data to determine receptor number and affinity. Because this kind of experiment used to be analyzed with Scatchard plots (more accurately attributed to Rosenthal), they are sometimes called "Scatchard experiments".

The analyses depend on the assumption that you have allowed the incubation to proceed to equilibrium. This can take anywhere from a few minutes to many hours, depending on the ligand, receptor, temperature, and other experimental conditions. The lowest concentration of radioligand will take the longest to equilibrate. When testing equilibration time, therefore, use a low concentration of radioligand (perhaps 10-20% of the KD).