 In the transportation or detection of diatomic gases, the gas binds to the heme iron.During the detection of diatomic gases, the binding of the gas ligand to the heme iron induces conformational changes in the surrounding protein.In general, diatomic gases only bind to the reduced heme, as ferrous Fe(II) while most peroxidases cycle between Fe(III) and Fe(IV) and hemeproteins involved in mitochondrial redox, oxidation-reduction, cycle between Fe(II) and Fe(III).