Measurement of Ligand–G Protein-coupled Receptor Interactions

Radioligand binding assays take advantage of the ability to detect the decay of radioactive material, which can be incorporated into a ligand of choice. The interaction of such a radioligand with a receptor preparation can subsequently be determined by capturing and measuring the amount of radioactivity present. Radioligand binding assays can be used to estimate molecular parameters, such as the density of receptors present in a tissue or cellular preparation or the affinity of a ligand for binding to a receptor. The simplest scheme that describes the binding of a ligand to its receptor is based on the law of mass action: A + R Kon −−−→ ←−−− Koff AR