Assay Method Information

Assay Name:  CDK4/Cyclin D3 Mobility Shift Assay
Description:  The purpose CDK4/Cyclin D3 assay is to evaluate the inhibition (% inhibition, Kiapp and Ki values) in the presence of small molecule inhibitors by using a fluorescence based microfluidic mobility shift assay. CDK4/Cyclin D3 catalyzes the production of ADP from ATP that accompanies the phosphoryl transfer to the substrate peptide 5-FAM-Dyrktide (5-FAM-RRRFRPASPLRGPPK) (SEQ ID NO:2). The mobility shift assay electrophoretically separates the fluorescently labeled peptides (substrate and phosphorylated product) following the kinase reaction. Both substrate and product are measured and the ratio of these values is used to generate % Conversion of substrate to product by the LabChip EZ Reader. Typical reaction solutions contained 2% DMSO (±inhibitor), 10 mM MgCl2, 1 mM DTT, 2 mM ATP, 0.005% TW-20, 3 μM 5-FAM-Dyrktide, 2 nM (active sites) CDK4/Cyclin D3 in 40 mM HEPES buffer at pH 7.5.Inhibitor Ki determinations for non-phosphorylated CDK4/Cyclin D3 (LJIC-2007/2010) were initiated with the addition of ATP (50 μL final reaction volume), following a twelve minute pre-incubation of enzyme and inhibitor at 22° C. in the reaction mix. The reaction was stopped after 35 minutes by the addition of 50 μL of 25 mM EDTA. 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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