CHEMBL3887275

Time-Resolved Fluorescence Resonance Energy Transfer (TR-FRET) Assay: Btk kinase activity was determined using a time-resolved fluorescence resonance energy transfer (TR-FRET) methodology. Measurements were performed in a reaction volume of 50 uL using 96-well assay plates. Kinase enzyme, inhibitor, ATP (at the Km for the kinase), and 1 uM peptide substrate (Biotin-AVLESEEELYSSARQ-NH2) were incubated in a reaction buffer composed of 20 mM Tris, 50 mM NaCl, MgCl2 (5-25 mM depending on the kinase), MnCl2 (0-10 mM), 1 mM DTT, 0.1 mM EDTA, 0.01% bovine serum albumin, 0.005% Tween-20, and 10% DMSO at pH 7.4 for one hour. The reaction was quenched by the addition of 1.2 equivalents of EDTA (relative to divalent cation) in 25uL of 1x Lance buffer (Perkin-Elmer). Streptavidin-APC (Perkin-Elmer) and Eu-labeled p-Tyr100 antibody (Perkin-Elmer) in 1x Lance buffer were added in a 25 uL volume to give final concentrations of 100 nM and 2.5 nM, respectively, and the mixture was allowed to incubate for one hour.