Mv. Kroger-ohlsen et al., Acid-catalysed autoreduction of ferrylmyoglobin in aqueous solution studied by freeze quenching and ESR spectroscopy, FREE RAD RE, 30(4), 1999, pp. 305-314
Decay of the hypervalent muscle pigment ferrylmyoglobin, formed by activati
on of metmyoglobin by hydrogen peroxide, was found, when studied by a combi
nation of ESR and UV/VIS spectroscopy in aqueous solution at physiological
pH, to proceed by parallel second- and first-order kinetics. At pH below 6.
5 a sharp ESR signal (g = 2.003) with an increasing intensity for decreasin
g pH were observed in solutions frozen in liquid nitrogen, and a broad sign
al (g = 2.005) was seen throughout the studied pH range also in frozen solu
tions. The g = 2.005 signal is suggested to arise from an intermediate form
ed in an intramolecular rate-determining electron-transfer in ferrylmyoglob
in, whereas the g = 2.003 signal is caused by a radical formed in a proton-
assisted electron-transfer initiating the specific acid-catalysed autoreduc
tion.