title: Acid-catalysed autoreduction of ferrylmyoblobin in aqueous solution studied by freeze quenching and ESR spectroscopy.
abstract: Decay of the hypervalent muscle pigment ferrylmyoglobin, formed by activation of metmyoglobin by hydrogen peroxide, was found, when studied by a combination 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 decreasing pH were observed in solutions frozen in liquid nitrogen, and a broad signal (g = 2.005) was seen throughout the studied pH range also in frozen solutions. The g = 2.005 signal is suggested to arise from an intermediate formed in an intramolecular rate-determining electron-transfer in ferrylmyoglobin, whereas the g 2.003 signal is caused by a radical formed in a proton-assisted electron-transfer initiating the specific acid-catalysed autoreduction.
authors.affiliation: Department of Dairy and Food Science, Royal Veterinary and Agricultural University, Frederiksberg C, Denmark.
authors.forename: M V
authors.initials: MV
authors.lastname: Kröger-Ohlsen
authors.forename: M L
authors.initials: ML
authors.lastname: Andersen
authors.forename: L H
authors.initials: LH
authors.lastname: Skibsted
mesh_terms: D004578:Electron Spin Resonance Spectroscopy; D005609:Free Radicals; D005615:Freezing; D006861:Hydrogen Peroxide / Q000737:chemistry; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D008786:Metmyoglobin / Q000737:chemistry*; D010084:Oxidation-Reduction; D012996:Solutions; D013053:Spectrophotometry; D013056:Spectrophotometry, Ultraviolet; D014867:Water
chemical_list: D005609:Free Radicals; D012996:Solutions; C028048:ferrylmyoglobin; D014867:Water; D008786:Metmyoglobin; D006861:Hydrogen Peroxide