CHEMBL5729944

Fluorescence Polarization Assay: A Bak BH3 peptide (F-BakBH3) (GQVGRQLAIIGDDINR (SEQ ID NO:1)) was labeled at the N-terminus with fluorescein isothiocyanate (FITC) (Molecular Probes) and purified by HPLC. For competitive binding assays, 100 nM GST-BCL-XL DTM protein was preincubated with the tested compound at varying concentrations in 47.5 uL PBS (pH=7.4) in 96-well black plates at room temperature for 10 min, then 2.5 uL of 100 nM FITC-labeled Bak BH3 peptide was added to produce a final volume of 50 uL. The wild-type and mutant Bak BH3 peptides were included in each assay plate as positive and negative controls, respectively. After 30 min incubation at room temperature, the polarization values in millipolarization units were measured at excitation/emission wavelengths of 480/535 nm with a multilabel plate reader (PerkinElmer). IC50 was determined by fitting the experimental data to a sigmoidal dose-response nonlinear regression model.