EPR analysis of the resting CYP121 enzyme (250 μm)
reacting with peracetic acid (2 mm). The resting CYP121
enzyme is present as a heterogeneous low-spin ferric heme species
(black trace). CYP121 was mixed in a 1:1 ratio and quenched
in liquid ethane after reaction times of 100 ms (navy trace),
2 s (blue), and 20 s (cyan). The reaction
generated at least one high-spin species at g = 6.67, 5.77, and 2 that
increased in intensity after longer reaction times. EPR spectra were obtained
at 5 K, 9.6-GHz microwave frequency, and 1-milliwatt microwave power.
mT, milliteslas.