Assay Method Information

Assay Name:  Functional Assay (GTPgammaS Binding)
Description:  The EC50 and Imax for mu opioid receptors was determined using a [I35S]GTPgammaS binding assay. This assay measures the functional properties of a compound by quantifying the level of G-protein activation following agonist binding in studies using stably transfected cells, and is considered to be a measure of the efficacy of a compound. Membranes from CHO (Chinese Hamster Ovary) cells that stably expressed the cloned human Mu opioid receptor were used in the experiments. Specifically, in a final volume of 0.5 mL, 12 different concentrations of each test compound were incubated with 7.5 ug of CHO cell membranes that stably expressed the human mu opioid receptor. The assay buffer consisted of 50 mM Tris-HCl, pH 7.4, 3 mM MgCl2, 0.2 mM EGTA, 3 uM GDP, and 100 mM NaCl. The final concentration of [35S]GTPgammaS was 0.080 nM. Nonspecific binding was measured by inclusion of 10 uM GTPgammaS. Binding was initiated by the addition of the membranes.
Affinity data for this assay

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