Ferrous dioxygen complex stabilization

Ledbetter AP, McMillan K, Roman LJ, Masters BS, Dawson JH, Sono M (1999) Low-temperature stabilization and spectroscopic characterization of the dioxygen complex of the ferrous neuronal nitric oxide synthase oxygenase domain. Biochemistry 38 8014-8021... 

In the case of IDO, on the other hand, a relatively stable binary complex with O2, i.e., the oxygenated enzyme, can be formed even in the absence of substrate [192, 201]. The enzyme-oxygen species, (E O2 Fe -02 or Fe -02"), exhibits absorption maxima at 415, 542, and 576 nm as shown in Fig. 23 [203]. The binary species is formed by the native ferric enzyme with superoxide anion [201] or by the binding of dioxygen to the ferrous enzyme [166, 178, 201, 202, 204]. Sono stabilized the IDO-O2 binary complex at -30 oc [203] and observed the spectral change by addition of tryptophan to the binary complex. 

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