Functional coupling assays

Microarrays are incubated with the specific ligand of a G protein-coupled receptor and  [35S]GTPγS. The ligand activates the receptor and the G protein that exchanges GDP by the nonhydrolyzable analog of GTP, [35S]GTPγS. Once unbound radioligand is removed, the microarrays are dried and exposed to a radiosensitive film with a [14C] standard that allows to calibrate results. After being developed is quantified and analyzed employing image analysis software.