Figure 5.

Assessment of experimental uncertainty in the determination of IC50 for PPI inhibitors using different assays. (A) Inhibitors of various bromodomains, measured by both fluorescence polarization and fluorescence resonance energy transfer (TR-FRET). Two regression lines are shown (y = αx + β and y = αx), highlighting that absence of the β coefficient substantially lowers r². (B) Inhibitors of the MDM2/p53 interaction, measured by both ELISA and cell proliferation assays. (C) Distribution of fold differences in IC50 for 72 inhibitors targeting various protein–protein interactions that have been measured by two (or more) different experimental methods.