Quenching of singlet oxygen luminescence by fatty acids and lipids: Contribution of physical and chemical mechanisms

Abstract

By the use of photosensitized luminescence of singlet oxygen ( 1O 2) in CCl 4, the rate constants for quenching 1O 2 by saturated and unsaturated fatty acids were determined. The experimental data suggest that saturated fatty acids quench 1O 2 via a physical mechanism, presumably as a result of energy transfer to the vibrational sublevels of CH- and COOH-groups. Unsaturated fatty acids are predominantly chemical quenchers. The relative contribution of the physical quenching depends on the number of double bonds in fatty acid molecules. It was found that the quenching activity of egg phosphatidylcholine is approximately equal to the sum of quenching activities of the lipid fatty acids. The data obtained may be used for prediction of the efficiency of singlet oxygen quenching by any lipids whose fatty acid composition is known.