Continuous measurement of oxygen consumption by linoleic acid membranes exposed to free radicals generated by γ-radiation

Vesicles enclosed by membranes prepared from linoleic acid were exposed in the chamber of an oxygen electrode to free radicals generated by ⁶⁰Co γrays. Oxidation was observed by oxygen consumption, conjugated diene formation, and tri-iodide assay for hydroperoxides. There was a dose-dependent lag period before the onset of rapid peroxidation. The radiation chemical yields (G-values) ranged from 4.45 to 19.37 μmolJ^-1 for maximum rates of oxygen consumption and from 2.18 to 16.37 μmolJ^-1 for maximum rates of hydroperoxide production when the radiation dose-rate was varied between 5.39 and 0.14 Gy min^-1. The magnitudes of these G-values and the linear relationship between yield of hydroperoxide and (dose-rate)^1/2 were indicative of a chain mechanism for peroxidation operating in membranes. The lack of congruence between the amount of oxygen consumed and hydroperoxide formed suggested that the oxygen consumed in membrane oxidation led to the formation of oxidized derivatives of linoleic acid additional to the hydroperoxides.