Fig. 3.

Mechanisms that may be operative in the nitration of Tyr residues and heme groups of hemoproteins. The pathways have been exemplified for Lb but are also extensive to Mb and Hb. Some intermediates are indicated in square brackets only to mean that they are formed inside the heme pocket but, except for the nitrite and peroxynitrite complexes, are not necessarily bound to the heme. Experiments designed to test these pathways are described in the text. Additional abbreviations: Lb³⁺, ferric Lb; Lb⁴⁺=O, ferryl Lb; Lb³⁺(nitrovinyl), ferric Lb bearing a vinyl-bound NO₂ group in the heme.