[35S]-GTPγS binding, also known as a GTP exchange assay, is a powerful method used to measure the activation of G protein-coupled receptors (GPCRs) by a ligand.
[35S]-GTPγS binding can be used to:
Determine if a ligand can activate a GPCR of interest
Single concentration screening or dose-response to determine pharmacological values of potency (EC50) & efficacy (EMAX)
Determine full, partial, or inverse agonist and antagonist activity