Assay Method Information

Assay Name:  [35S] GTPgammaS Binding Assays
Description:  Compounds were loaded in a 384 Falcon v-bottom plate (0.5 ul/well in a 11 point, 3-fold dilution). Membranes prepared from S1P1/CHO cells or EDG3-Gal5-bla HEK293T cells (EDG3 equivalent S1P3) were added to the compound plate (40 ul/well, final protein 3 ug/well) with MULTIDROP. [35S] GTP (1250 Ci/mmol, Perkin Elmer) was diluted in assay buffer: 20 mM HEPES, pH7.5, 10 mM MgCl2, 150 mM NaCl, 1 mM EGTA (ethylene glycol tetraacetic acid), 1 mM DTT (Dithiothreitol), 10 uM GDP, 0.1% fatty acid free BSA, and 10 ug/ml Saponin to 0.4 nM. 40 ul of the [35S] GTP solution was added to the compound plate with a final concentration of 0.2 nM. The reaction was kept at room temperature for 45 min. At the end of incubation, all the mixtures in the compound plate were transferred to Millipore 384-well FB filter plates via the VELOCITY11 Vprep liquid handler. The filter plate was washed with water 4 times by using the manifold Embla plate washer and dried at 60° C. for 45 min. MicroScint 20 scintillation fluid (30 ul) was added to each well for counting on the Packard TOPCOUNT. EC50 is defined as the agonist concentration that corresponds to 50% of the Ymax (maximal response) obtained for each individual compound tested.
Affinity data for this assay
 

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