| Assay Method Information | |
| | Competitive Inhibition Assay Using [I125]-NDP-a-MSH |
| Description: | A competitive inhibition binding assay is performed using membrane homogenates prepared from HEK-293 cells that express recombinant hMC4-R, hMC3-R, or hMC5-R, and from B-16 mouse melanoma cells (containing endogenous MC1-R). In some instances, HEK-293 cells that express recombinant hMC1-R were employed. In the examples that follow, all MC3-R, MC4-R and MC5-R values are for human recombinant receptors. MC1-R values are for B-16 mouse melanoma cells, unless the heading is hMC1-R, in which case the value is for human recombinant MC1-R. Assays were performed in 96 well GF/B Millipore multiscreen filtration plates (MAFB NOB10) pre-coated with 0.5% bovine serum albumin (Fraction V). Membrane homogenates were incubated with 0.2 nM (for hMC4-R) 0.4 nM (for MC3-R and MC5-R) or 0.1 nM (for mouse B16 MC1-R or hMC1-R) [I125]-NDP-α-MSH (Perkin Elmer) and increasing concentrations of test peptides of the present invention in buffer containing 25 mM HEPES buffer (pH 7.5) with 100 mM NaCl, 2 mM CaCl2, 2 mM MgCl2, 0.3 mM 1,10-phenanthroline, and 0.2% bovine serum albumin. After incubation for 60 minutes at 37° C., the assay mixture was filtered and the membranes washed three times with ice-cold buffer. Filters were dried and counted in a gamma counter for bound radioactivity. Non-specific binding was measured by inhibition of binding of [I125]-NDP-α-MSH in the presence of 1 uM NDP-α-MSH. Maximal specific binding (100%) was defined as the difference in radioactivity (cpm) bound to cell membranes in the absence and presence of 1 uM NDP-α-MSH. Radioactivity (cpm) obtained in the presence of test compounds was normalized with respect to 100% specific binding to determine the percent inhibition of [I125]-NDP-α-MSH binding. Each assay was conducted in triplicate and the actual mean values are described, with results less than 0% reported as 0%. Ki values for test peptides of the present invention were determined using Graph-Pad Prism curve-fitting software. |
| Affinity data for this assay | |
|---|---|
| If you find an error in this entry please send us an E-mail | |