Electron capture by oxyhaemoglobin: an e. s. r. study

Abstract

Exposure of aqueous glasses containing oxyhaemoglobin to 60 Co γ rays at 77 K gave two similar paramagnetic centres whose electron spin resonance (e. s. r.) spectra resembled those of low-spin ferric derivatives. These were shown to be formed in the α and β chains by electron capture. The use of oxygen labelled with 17 O showed the presence of two inequiva­lent oxygen atoms and it is shown that the unpaired electron has consider­able spin density on the dioxygen ligand as well as on iron. When warmed above 77 K two new paramagnetic centres were formed, possibly as a result of protonation, before the formation of normal high-spin methaemoglobin, presumably by loss of HO 2 ¯ . Oxymyoglobin gave comparable centres.