Kinetics of O2(1Δg) photo-oxidation reactions in egg-yolk lecithin vesicles

Abstract

The photosensitized oxidation of single bilayer vesicles of egg-yolk lecithin by singlet oxygen is investigated. The isotopic enhanced lifetime of singlet oxygen in heavy water, and the inhibitory effect of azide ions, are both used to examine the O₂(¹Δ_g) diffusion characteristics. The rate of photo-oxidation of unsaturated fatty acid is shown to be strongly dependent on the precise location of the sensitizer in the bilayer. Rate constants for the interaction of singlet oxygen with the lipid, with the acceptor 9,10-dimethylanthracene and with azide are determined to be 7.5 × 10⁵, 3.2 × 10⁸ and 1.0 × 10⁸ dm³ mol^–1 s^–1, respectively.