CONTINUOUS MEASUREMENT OF OXYGEN-CONSUMPTION BY LINOLEIC-ACID MEMBRANES EXPOSED TO FREE-RADICALS GENERATED BY GAMMA-RADIATION

Vesicles enclosed by membranes prepared from linoleic acid were expose d in the chamber of an oxygen electrode to free radicals generated by Co-60 gamma-rays. Oxidation was observed by oxygen consumption, conjug ated diene formation, and tri-iodide assay for hydroperoxides. There w as a dose-dependent lag period before the onset of rapid peroxidation. The radiation chemical yields (G-values ranged from 4.45 to 19.37 mu- mol J-1 for maximum rates of oxygen consumption and from 2.18 to 16.37 mumol J-1 for maximum rates of hydroperoxide production when the radi ation dose-rate was varied between 5.39 and 0.14 Gy min-1. The magnitu des of these G-values and the linear relationship between yield of hyd roperoxide and (dose-rate)1/2 were indicative of a chain mechanism for peroxidation operating in membranes. The lack of congruence between t he amount of oxygen consumed and hydroperoxide formed suggested that t he oxygen consumed in membrane oxidation led to the formation of oxidi zed derivatives of linoleic acid additional to the hydroperoxides.