PULSE RADIOLYSIS STUDIES IN MODEL LIPID SYSTEMS: FORMATION AND BEHAVIOR OF PEROXY RADICALS IN FATTY ACIDS

Abstract

Abstract— Radiolytic formation and peroxidation of fatty acid radicals have been investigated by pulse radiolysis techniques in oleate, linoleate, linolenate and arachidonate systems. A strong absorption band at 280 nm associated with conjugated radicals, R conj , formed in polyunsaturated fatty acid moieties has been used as a probe for kinetic processes occurring at doubly allylic sites in the hydrocarbon chain. Formation of R conj by O ‐ has been found to be more efficient than the less selective OH radical. Peroxidation of R conj is shown to be somewhat slower, ( k R + O 2 ˜ 3 × 10 8 M ‐1 s ‐1 ), than O 2 reactions with radicals in oleate ( k R + O 2 = 1 × 10 9 M ‐1 s ‐1 ). Peroxy radicals generated in these reactions disappear slowly by essentially second order processes (2 k RO 1 ˜ 10 7 M ‐1 s ‐1 ). The superoxide radical, O ‐ 2 , shows little if any reactivity towards 0.01 M linolenate or arachidonate over periods of 20 s.