After virtual screening of the test set, 40 chemical compounds (Sigma-Aldrich Co. LLC) were purchased for experimental test through fluorescence resonance energy transfer (FRET) assay based on the results of conventional consensus scoring and PCA scoring. According to the previously described method [65] , during the assay, compounds were diluted to 8 different concentrations and incubated 60 minutes at room temperature. Additional measurements were performed in the presence of detergent or with an incubation time of only 3 min to check for nonspecific effects (e.g., compound aggregation [66, 67] ). Briefly, fluorescence progress curves of 30 mL reaction volumes were measured on a Gen5 TM ELISA reader (BioTekH Instruments, Inc.) upon excitation at 545 nm and emission at 580 nm in 384well microtiter plates (Corning, 3654). Linear regression analysis was calculated with the SPSS 16.0 software.