Assay Method Information

Assay Name:  Radioligand Binding Assay
Description:  HEK293 stably expressing human orexin 2 receptor (Genebank accession number NM_001526) were grown to confluency in DMEM (Hyclone, cat #SH30022), 10% FBS, 1x Pen/Strep, 1x NaPyruvate, 10 mM HEPES, 600 ug/ml G418 media on 150 cm2 tissue culture plates, washed with 5 mM EDTA in PBS (HyClone Dulbecco's Phosphate Buffered Saline 1x with Calcium and Magnesium, Cat #SH30264.01, hereafter referred to simply as PBS) and scraped into 50 ml tubes. After centrifugation (2KxG, 5 min at 40° C.), the supernatant was aspirated and the pellets frozen and stored at -800° C. Cells were resuspended in PBS in the presence of 1 tablet of protease inhibitor cocktail (Roche, Cat. #11836145001) per 50 mL. Each cell pellet from a 15 cm plate was resuspended in 10 mL, stored on ice, and homogenized for 45 sec just prior to addition to the reactions. Competition binding experiments in 96 well polypropylene plates were performed using [3H]-EMPA (Moraveck Corporation, specific activity=29.6 Ci/mmol), diluted to a 5 nM concentration in PBS (2 nM final concentration). Compounds were solubilized in 100% DMSO (Acros Organics, Cat. #61042-1000) and tested over a range of 7 concentration (from 0.1 nM to 10 uM). The final concentration of DMSO in the reactions is equal to or less than 0.1%. Total and nonspecific binding was determined in the absence and presence of 10 uM almorexant. The total volume of each reaction is 200 uL (20 uL of diluted compounds, 80 uL of [3H]-EMPA diluted in PBS and 100 uL of the cell suspension). Reactions were run for 60 min at room temperature and terminated by filtration through GF/C filter plates (PerkinElmer, Cat. #6005174) presoaked in 0.3% polyethylenimine using the cell harvester (PerkinElmer Filtermate). The plates were washed 3 times by aspirating 30 ml PBS through the plates. Plates were dried in 55° C. oven for 60 min, scintillation fluid was added, and the radioactivity was counted on a Topcount (Packard).
Affinity data for this assay

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