The electron-transfer mechanism of autoxidation for hemoglobin, myoglobin, and their iron(II) cyclidene models

A kinetic study of the autoxidation of iron(II) cyclidenes as functions of O2 pressure and O2-binding cavity size reveals a new mechanism for this reaction and for those of hemoglobin and myoglobin. Apart from the previously established inverse relation of O2 pressure to autoxidation rates, the study also shows that opening up the cavity allows more O2 to bind to iron, but that the O2 that oxidizes the iron(II) is not bound. This suggests a mechanism involving electron-transfer rather than superoxide dissociation or displacement. The same mechanism is observed for hemoglobin and myoglobin.