Screen Quest? FRET No Wash cAMP Assay Kit. Screen Quest? FRET No Wash cAMP Assay Kit provides a convenient assay method for monitoring the activation of adenylyl cyclase in G-protein coupled receptor systems. Compared to other commercial ELISA cAMP assay kits, this homogenous cAMP assay kit does not require a wash step or the acetylation step. The assay is based on the competition for a fixed number of anti-cAMP antibody binding sites between the fluorescent cAMP tracer and non-labeled free cAMP. Free cAMP displaces the fluorescent cAMP tracer from the HRP-cAMP/anti-cAMP antibody complex. The anti-cAMP antibody is labeled with our TR Fluor? Eu while the cAMP tracer contains our trFluor? 650. In the absence of cAMP, trFluor? 650-cAMP conjugate is bound to TR Fluor? Eu-labeled anti-cAMP antibody exclusively to have a strong FRET. However, the unlabeled free cAMP in the test sample competes for the TR Fluor? Eu-labeled anti-cAMP antibody conjugate, therefore inhibits the binding of trFluor? 650-cAMP to anti-cAMP antibody. The trFluor? 650 labeled cAMP tracer only has fluorescence lifetime of nanosecond while TR Fluor? Eu-labeled anti-cAMP antibody-bound fluorescent cAMP tracer has much longer fluorescence lifetime value due to the TR-FRET. The magnitude of FRET is proportional to the concentration of cAMP in a sample. The assay can be performed in a convenient 96-well or 384-well microtiter-plate format.