| Assay Method Information | |
| | Chelation-Enhanced Fluorescence (CHEF) Assay |
| Description: | CDK4/Cyclin D1 and CDK6/Cylcin D3: The Chelation-Enhanced Fluorescence (CHEF) monitors the phosphorylation state in real time where the level of fluorescence is directly proportional to the amount of phosphorylated substrate. CHEF exploits a synthetic α-amino acid with a side chain bearing an 8-hydroxyquinoline derivative (sulfonamido-oxine, Sox) which, upon coordination to Mg(II), relays information on the phosphorylation state of a proximal serine, threonine or tyrosine residue in peptide-based kinase substrates. Phosphorylation of a specific peptide (Catalog # AQT0258) from AssayQuant Technologies results in an increase in fluorescence at the excitation and emission wavelengths of 360 nm Ex/485 nm Em.Examples along with DMSO (negative) and Palbociclib (positive) controls were added to 384-well plates at 100-fold their final concentrations followed by the addition of 10 nM CDK4/Cyclin D1 (LJIC-2007F1) or 10 nM CDK6/Cyclin D3 (LJIC-2009H2) for a 20 minute pre-incubation in assay buffer containing 40 mM HEPES, 1 mM Dithiothreito (DTT, 10 mM MgCl2, 1% Glycerol, 0.1% BSA. Enzyme reactions were initiated by the addition of AssayQuant Technologies peptide and ATP substrates (10 μM CHEF peptide (Catalog # AQT0258), 2 mM ATP) and allowed to proceed for 2 hours followed by fluorescence read of the reaction. Ki determinations were made from a plot of the fractional velocity as a function of inhibitor concentration fit to the Morrison equation with the enzyme concentration as a variable. |
| Affinity data for this assay | |
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