Assay Method Information

Assay Name:  Multiplexed dose response screen for small molecule regulators of Bcl-2 family protein interactions, specifically Bim-Bcl-XL.
Description:  The HTS assay was conducted in 384-well microplates in a total assay volume per well of 10.1 microliters (5 microliters of bead mixture, 0.1 microliters of test compound, and 5 microliters of 100 nM F-Bim in HPSMTB). Controls, which contained bead mixture and F-Bim but no test compound, were located in columns 1 and 2 on each plate. Plates were placed horizontal axis on rotators and incubated for 1-2 hours at 4 degrees C. A glutathione-only bead set control (no associated GST-protein) was incorporated into each well as a fluorescence scavenger to determine inherent fluorescent properties (at 530 nm emission) of the test compounds. Specificity of F-Bim binding was determined with a Positive Control using a block of the F-Bim fluor with a non-fluoresceinated Bim peptide. Sample acquisition and preliminary analysis is conducted with the HyperCyt(R) high throughput flow cytometry platform. The stream of particles is excited at 488 nm and 635 nM, and flow cytometric data of light scatter and fluorescence emission at 530 +/- 20 nm (FL1) and emission at 665 +/- 10 nm (FL8) are collected on a Cyan Flow Cytometer (Dako). Analysis of the time-resolved acquisition data file uses IDLeQuery software to merge the flow cytometry data files with compound worklist files generated by HyperSip software. In dose response experiments, the assay was performed without compound and with nine different concentrations of compound, from 10 nanoM to 100 microM, to produce a series of 9 data points. IDLeQuery calculates the median channel fluorescence (MCF) for each of these ligand concentrations, generating competition curves. Ligand competition curves were fitted by Prism# software (GraphPad Software, Inc., San Diego, CA) using nonlinear least-squares regression in a sigmoidal dose response model with variable slope, also known as the four parameter logistic equation. Curve fit statistics were used to determine the concentration of added test compound competitor that inhibited fluorescent ligand binding by 50 percent (EC50, microM)Compounds with EC50 less than 10 microM and magnitude of response greater than 40% (i.e., Bottom of sigmoidal curve < 0.6 * Top of sigmoidal curve, listed as FIT_PERCENT_SPAN) were said to be "Active".
Affinity data for this assay
 

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