Table 1. Identification of Heme Binding Functional Groups Using UV–Vis Spectroscopy^a.

^aAnalogues were prepared as 0.1–1 mM stocks in DMSO-d₆. The change in the wavelength of the Soret band (Δλ_max, nm) of CYP121 (5 μM) was calculated as the difference of that found in the presence of analogues compared to 1% v/v DMSO-d₆ alone (λ_max = 416.5 nm). Binding affinities (K_D) for selected compounds were calculated from the titration of compounds (0.2 μL aliquots of 10–100 mM stocks) into CYP121 (5 μM). Full details are provided in the Experimental Section.