Lipid peroxidation-dependent chemiluminescence from the cyclization of alkylperoxyl radicals to dioxetane radical intermediates.
This work reveals a novel mechanism for triplet carbonyl formation (and hence chemiluminescence) during lipid peroxidation, whose chemiluminescence has been attributed to both triplet carbonyls and singlet oxygen. As a model for polyunsaturated fatty acid hydroperoxides, we have synthesized 3-hydroperoxy-2,3-dimethyl-1-butene by photooxygenation of tetramethylethylene. One-electron oxidation of this hydroperoxide with heme proteins and peroxynitrite to the corresponding alkylperoxyl radical results in chemiluminescence, both direct and 9,10-dibromoanthracene-2-sulfonate-sensitized, the latter attributed to the formation of triplet acetone. It is postulated that triplet acetone results from the cyclization of the alkylperoxyl radical to a dioxetane radical intermediate followed by its thermolysis. This is supported by EPR spin-trapping experiments in which discrimination between carbon-centered radicals derived from the alkyloxyl and alkylperoxyl radicals is achieved through the use of one-electron oxidants and reductants, e.g., FeII- and TiIII.
Tímmins
G S
GS
Department of Chemistry, University of York, U.K.
dos Santos
R E
RE
Whitwood
A C
AC
Catalani
L H
LH
Di Mascio
P
P
Gilbert
B C
BC
Bechara
E J
EJ
D004578:Electron Spin Resonance Spectroscopy; D005609:Free Radicals; D006735:Horseradish Peroxidase; D015227:Lipid Peroxidation; D008163:Luminescent Measurements
D005609:Free Radicals; D006735:Horseradish Peroxidase