P23 - Singlet molecular oxygen generated in dark biological process

Abstract

Ultraweak chemiluminescence arising from biomolecules oxidation has been attributed to the radiative deactivation of singlet molecular oxygen [1O2] and electronically excited triplet carbonyl products involving dioxetane intermediates. As examples, we will discuss the generation of 1O2 from lipid hydroperoxides, which involves a cyclic mechanism from a linear tetraoxide intermediate. The generation of 1O2 in aqueous solution via energy transfer from the excited triplet acetone arising from the thermodecomposition of dioxetane a chemical source, and horseradish peroxidase-catalyzed oxidation of 2-methylpropanal, as an enzymatic source, will also be discussed. The approach used to unequivocally demonstrate the generation of 1O2 in these reactions is the use of 18O-labeled hydroperoxide / triplet dioxygen (18[3O2]), the detection of labeled compounds by HPLC coupled to tandem mass spectrometry (HPLC-MS/MS) and the direct spectroscopic detection and characterization of 1O2 light emission. Characteristic light emission at 1,270nm, corresponding to the singlet delta state monomolecular decay was observed. Using18[3O2], we observed the formation of 18O-labeled 1O2 (18[1O2]) by the chemical trapping of 18[1O2]with the anthracene-9,10-diyldiethane-2,1-diyl disulfate disodium salt (EAS) and detected the corresponding 18O-labeled EAS endoperoxide usingHPLC-MS/MS. The combined use of the thermolysis of a water-soluble naphthalene endoperoxide as a generator of 18O labeled 1O2 and the sensitivity of HPLC-MS/MS allowed the study of 1O2reactivity toward biomolecules. Photoemission properties and chemical trapping clearly demonstrate that the production of hydroperoxide and excited carbonyls generates 18[1O2], and points to the involvement of 1O2 in physiological and pathophysiological mechanism.Supported by FAPESP (2012/12663-1), CAPES, INCT Redoxoma (FAPESP/CNPq/CAPES; 573530/2008-4), NAP Redoxoma (PRPUSP; 2011.1.9352.1.8), CEPID Redoxoma (FAPESP; 2013/07937-8).