| Assay Method Information | |
| | Bcl-2 and Bcl-xL Inhibition Assay |
| Description: | Fluorescein labeled BIM (81-106), BAK (72-87), and BID (79-99) peptides, named as Flu-BIM, Flu-BAK, and Flu-BID, respectively, were used as the fluorescent probes in FP assays for Bcl-2, Bcl-xL, and Mcl-1, respectively. By monitoring the total fluorescence polarization values of mixtures composed of fluorescent probes at fixed concentrations and proteins with increasing concentrations up to the full saturation, the Kd values of Flu-BIM to Bcl-2, Flu-BAK to Bcl-xL and Flu-BID to Mcl-1 were determined to be 0.55±0.15, 4.4±0.8 and 6.9±0.9 nM, respectively. Fluorescence polarization values were measured using the Infinite M-1000 plate reader (Tecan U.S., Research Triangle Park, N.C.) in Microfluor 1 96-well, black, round-bottom plates (Thermo Scientific). To each well, 1 nM of Flu-BIM, or 2 nM of Flu-BAK or 2 nM of Flu-BID and increasing concentrations of Bcl-2, or Bcl-xL, or Mcl-1 were added to a final volume of 125 μl in the assay buffer (100 mM potassium phosphate, pH 7.5, 100 μg/ml bovine γ-globulin, 0.02% sodium azide, Invitrogen, with 0.01% Triton X-100 and 4% DMSO). Plates were mixed and incubated at room temperature for 1 hour with gentle shaking to assure equilibrium. The polarization values in millipolarization units (mP) were measured at an excitation wavelength of 485 nm and an emission wavelength of 530 nm. Equilibrium dissociation constants (Kd) were then calculated by fitting the sigmoidal dose-dependent FP increases as a function of protein concentrations using Graphpad Prism 5.0 software (Graphpad Software, San Diego, Calif.). |
| Affinity data for this assay | |
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