Table 2.

Redox potential estimates of O₂ in aqueous solution, with complete ‘levelling’ by the catalytic site of cytochrome oxidase and with a more moderate 5% levelling.

O2 redox couple, electrons added	0/I	I/II	II/III	III/IV
Em H2O, pH 7 (V)a	−0.33	0.94	0.305	2.33
Em estimate oxidase, 100% levelling	0.81	0.81	0.81	0.81
Em estimate oxidase, 5% levelling	−0.27	0.93	0.33	2.25

^aBabcock & Wikstrom (1992).