TY - JOUR
T1 - Mechanism of light-induced oxidation of nitrosylmyoglobin
AU - Munk, Merete Bøgelund
AU - Huvaere, Kevin André Jurgen
AU - Van Bocxlaer, Jan
AU - Skibsted, Leif Horsfelt
PY - 2010/7/15
Y1 - 2010/7/15
N2 - Exposure of nitrosylmyoglobin (MbFeIINO), to light in the presence of oxygen increases rate of oxidation still with metmyoglobin (MbFeIII) as main product, as shown by electron paramagnetic resonance and visible absorption spectroscopy. Despite previous suggestions of interfering radical species, capable of initiating lipid oxidation in cured meat, no radical adducts were detected during photolysis in spin trapping experiments. Flash photolysis showed separation of myoglobin (MbFeII) and nitric oxide (NO{radical dot}) after excitation, followed by fast rebinding under anaerobic conditions. In the presence of oxygen, nitric oxide rebinding was inhibited suggesting formation of a nitrosyldioxyl-radical (ONOO{radical dot}). As NO{radical dot} failed to diffuse into bulk solution, ONOO{radical dot} formation is proposed to occur in the heme cavity in competition with NO{radical dot} rebinding and, to a lesser degree, O2 binding to yield MbFeIIO2. Subsequent oxidation of MbFeII to MbFeIII by ONOO{radical dot} was expected to result in the highly reactive peroxynitrite intermediate (ONOO-), of which occurrence would be characterized by typical chemical footprints, such as nitrated tyrosine or tryptophan residues. However, results from direct infusion mass spectrometry suggested neat conversion from nitrosylmyoglobin to metmyoglobin and questioned the existence of ONOO- as reaction product. Catalytic activity of the resulting ferric centre in MbFeIII, however, induces fast isomerisation of ONOO- to the stable nitrate, which was identified directly as ion m/z 62 or indirectly by adduct formation with MbFeIII.
AB - Exposure of nitrosylmyoglobin (MbFeIINO), to light in the presence of oxygen increases rate of oxidation still with metmyoglobin (MbFeIII) as main product, as shown by electron paramagnetic resonance and visible absorption spectroscopy. Despite previous suggestions of interfering radical species, capable of initiating lipid oxidation in cured meat, no radical adducts were detected during photolysis in spin trapping experiments. Flash photolysis showed separation of myoglobin (MbFeII) and nitric oxide (NO{radical dot}) after excitation, followed by fast rebinding under anaerobic conditions. In the presence of oxygen, nitric oxide rebinding was inhibited suggesting formation of a nitrosyldioxyl-radical (ONOO{radical dot}). As NO{radical dot} failed to diffuse into bulk solution, ONOO{radical dot} formation is proposed to occur in the heme cavity in competition with NO{radical dot} rebinding and, to a lesser degree, O2 binding to yield MbFeIIO2. Subsequent oxidation of MbFeII to MbFeIII by ONOO{radical dot} was expected to result in the highly reactive peroxynitrite intermediate (ONOO-), of which occurrence would be characterized by typical chemical footprints, such as nitrated tyrosine or tryptophan residues. However, results from direct infusion mass spectrometry suggested neat conversion from nitrosylmyoglobin to metmyoglobin and questioned the existence of ONOO- as reaction product. Catalytic activity of the resulting ferric centre in MbFeIII, however, induces fast isomerisation of ONOO- to the stable nitrate, which was identified directly as ion m/z 62 or indirectly by adduct formation with MbFeIII.
U2 - 10.1016/j.foodchem.2009.12.067
DO - 10.1016/j.foodchem.2009.12.067
M3 - Journal article
SN - 0308-8146
VL - 121
SP - 472
EP - 479
JO - Food Chemistry
JF - Food Chemistry
IS - 2
ER -