Methemoglobin azide

Figure 5. IR absorption spectra of carp azide methemoglobin at 20°C. In the R structure the azide stretching frequency at 2023 cm 1, characteristic of low-spin azide hemes, dominates. In the T structure two peaks of equal intensity appear at 2023 and 2046 cm 1, characteristic of low- and high-spin azide hemes, respectively (43).

Smith L, Kruszyna H, Smith RP. 1977. The effect of methemoglobin on the inhibition of cytochrome c oxidase by cyanide, sulfide or azide. Biochem Pharmacol 26 2247-2250. 

Tryptophan pyrrolase is claimed to be an iron-porphyrin protein which is reduced to its active ferrous form by peroxide. This activation may be analogous to the reduction of methemoglobin and of catalase-azide complex of the oxygenated ferrous forms by peroxide (Keilin and Hartree, 1950 and 1954). 

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