... stereochemistry of the iron-dioxygen bond in human HbO2by single-crystalX-ray analysis. In the a chain, the distance between Ne of His (E7) and the terminal oxygen atom (O-2) is found to be2.7 AÊ, and ... geometry favors a similar hydrogen bond as in oxymyoglobin [29]. In the b chain, however, Ne of His(E7) is located further away from both O-2 and O-1 (3.4 and 3.2 AÊ, respectively), i ndicating ... autoxi-dation of oxym yoglo bin and oxyhaemoglobin: oxidation, d isso-ciation, or displacement? Biochem. J. 223, 279±280.28. Shikama, K. (1990) Autoxidation of oxymyoglobin: a meetingpoint of the...