Fig. 2.

Difference spectra illustrate absorbance shifts associated with heteroatom coordination to the heme iron as (S)-orteronel is titrated into 100 nM CYP17A1 (shown). Similar shifts were observed for the other four nonsteroidal inhibitors evaluated (not shown). Spectra with increasing inhibitor concentrations are shown from low-to-high concentrations (red to blue/violet). The differences in absorbance between the resulting peak and trough (ΔAbsorbance) were used to evaluate the ligand binding affinity to CYP17A1.