| Assay Method Information | |
| | Competitive Binding Assay Using Eu-NDP-a-MSH |
| Description: | A competitive inhibition binding assay was performed employing Eu-NDP-α-MSH (PerkinElmer Life Sciences catalog No. AD0225) with determination by time-resolved fluorometry (TRF) of the lanthanide chelate. In comparison studies with [I125]-NDP-α-MSH, the same values, within experimental error ranges, were obtained for percent inhibition and Ki. Typically competition experiments to determine Ki values were conducted by incubating membrane homogenates prepared from HEK-293 cells that express recombinant hMC4-R with 9 different concentrations of test compounds of interest and 2 nM of Eu-NDP-α-MSH in a solution containing 25 mM HEPES buffer with 100 mM NaCl, 2 mM CaCl2, 2 mM MgCl2 and 0.3 mM 1,10-phenanthroline. After incubation for 90 minutes at 37° C., the reaction was stopped by filtration over AcroWell 96-well filter plates (Pall Life Sciences). The filter plates were washed 4 times with 200 uL of ice-cold phosphate-buffered saline. DELFIA Enhancement solution (PerkinElmer Life Sciences) was added to each well. The plates were incubated on a shaker for 15 minutes and read at 340 nm excitation and 615 nm emission wavelengths. Each assay was conducted in duplicate and mean values were utilized. Ki values were determined by curve-fitting with Graph-Pad Prism software using a one-site fixed-slope competition binding model. |
| Affinity data for this assay | |
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