Fig. 1.

Arrangement of the relevant cofactors [from the structure of carboxylated mammalian cytochrome c oxidase, Protein Data Bank ID code 1OCO (12)] and glossary of electron and CO transfer processes monitored in the experiments starting from the mixed-valence (a³⁺a₃²⁺–CO) enzyme. The ET arrows are tentatively drawn along a recently suggested through-space path (19). The figure was prepared by using rasmol (40).