Kinetics of the ferryl complex in NapI monitored by its absorbance at 320 nm. An
anoxic solution of NapI (1.2 mM), Fe(II) (1.1 mM), 2OG (6.0 mM) and 6.0 mM of
either L-Arg (black), 4,4-d2-L-Arg (red), or
5,5-d2-L-Arg (blue) was mixed at 5
°C with an equal volume of air-saturated buffer (giving ~ 0.19 mM final
[O2]). Regression fits to the data are shown as
solid lines. The equation for fitting assumes absorbance from two consecutive,
irreversible reactions, with isosbestic reactant and product and more intensely
absorbing intermediate.