Chemiluminescence of lipid vesicles supplemented with cytochrome c and hydroperoxide

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Abstract
The increase in light emission of hydroperoxide-supplemented cytochrome c observed on addition of lipid vesicles was related to the degree of unsaturation of the fatty acids of the phospholipids: dipalmitoyl phosphatidylcholine was without effects, whereas dioleoyl phosphatidylcholine and soybean phosphatidylcholine enhanced chemiluminescence 2- and 3-fold, respectively. Effects on light-emission were similar to those on O2 uptake. The chemiluminescence of the present system was sensitive to cyanide and to the radical trap 2,5-di-tert-butylquinol, indicating a catalytic activity of cytochrome c and the presence of free-radical species, respectively. Lipid-vesicle enhanced chemiluminescence showed different kinetic behaviors, apparently depending on unsaturation: 3 phases are described for soybean phosphatidylcholine, whereas only 1 phase was present in mixtures containing dipalmitoyl and dioleoyl phospholipids. Chemiluminescence of lipid vesicles supplemented with cytochrome c and hydroperoxide showed similar kinetic patterns with H2O2 and primary (ethyl) and tertiary (tert-butyl and cumene) hydroperoxides. Participation of singlet molecular oxygen, mainly in the phase III of chemiluminescence, is suggested by the increase of light-emission by 1,4-diazabicyclo[2.2.2]-octane as well as by data from spectral analysis.