title: Biological hydroperoxides and singlet molecular oxygen generation.
abstract: The decomposition of lipid hydroperoxides (LOOH) into peroxyl radicals is a potential source of singlet molecular oxygen ((1)O(2)) in biological systems. Recently, we have clearly demonstrated the generation of (1)O(2) in the reaction of lipid hydroperoxides with biologically important oxidants such as metal ions, peroxynitrite and hypochlorous acid. The approach used to unequivocally demonstrate the generation of (1)O(2) in these reactions was the use of an isotopic labeled hydroperoxide, the (18)O-labeled linoleic acid hydroperoxide, the detection of labeled compounds by HPLC coupled to tandem mass spectrometry (HPLC-MS/MS) and the direct spectroscopic detection and characterization of (1)O(2) light emission. Using this approach we have observed the formation of (18)O-labeled (1)O(2) by chemical trapping of (1)O(2) with anthracene derivatives and detection of the corresponding labeled endoperoxide by HPLC-MS/MS. The generation of (1)O(2) was also demonstrated by direct spectral characterization of (1)O(2) monomol light emission in the near-infrared region (lambda = 1270 nm). In summary, our studies demonstrated that LOOH can originate (1)O(2). The experimental evidences indicate that (1)O(2) is generated at a yield close to 10% by the Russell mechanism, where a linear tetraoxide intermediate is formed in the combination of two peroxyl radicals. In addition to LOOH, other biological hydroperoxides, including hydroperoxides formed in proteins and nucleic acids, may also participate in reactions leading to the generation (1)O(2). This hypothesis is currently being investigated in our laboratory.
authors.affiliation: Departamento de Bioquímica, Instituto de Química, Universidade de São Paulo. São Paulo, SP, Brazil.
authors.forename: Sayuri
authors.initials: S
authors.lastname: Miyamoto
authors.forename: Graziella E
authors.initials: GE
authors.lastname: Ronsein
authors.forename: Fernanda M
authors.initials: FM
authors.lastname: Prado
authors.forename: Miriam
authors.initials: M
authors.lastname: Uemi
authors.forename: Thais C
authors.initials: TC
authors.lastname: Corrêa
authors.forename: Izaura N
authors.initials: IN
authors.lastname: Toma
authors.forename: Agda
authors.initials: A
authors.lastname: Bertolucci
authors.forename: Mauricio C B
authors.initials: MC
authors.lastname: Oliveira
authors.forename: Flávia D
authors.initials: FD
authors.lastname: Motta
authors.forename: Marisa H G
authors.initials: MH
authors.lastname: Medeiros
authors.forename: Paolo Di
authors.initials: PD
authors.lastname: Mascio
mesh_terms: D002462:Cell Membrane / Q000737:chemistry; D004247:DNA / Q000737:chemistry; D006861:Hydrogen Peroxide / Q000737:chemistry; D008054:Lipid Peroxides / Q000737:chemistry*; D015394:Molecular Structure; D016877:Oxidants / Q000737:chemistry*; D011506:Proteins / Q000737:chemistry; D026082:Singlet Oxygen / Q000737:chemistry*
chemical_list: D008054:Lipid Peroxides; D016877:Oxidants; D011506:Proteins; D026082:Singlet Oxygen; D004247:DNA; D006861:Hydrogen Peroxide