QUENCHING OF SINGLET OXYGEN BY HUMAN PLASMA

Abstract— Direct measurements of the decay of singlet oxygen phosphorescence at 1270 nm were made in human plasma diluted with various amounts of deuterium oxide. The Stern‐Volmer plot of the singlet oxygen lifetimes was linear up to 15% plasma concentration (vol/vol). Extrapolation of these measurements to 100% plasma content gave a singlet oxygen lifetime of 1.04 ± 0.03 JJLS in human plasma. Biological molecules accounted for 77% of the total singlet oxygen quenching while water accounted for 23% of the quenching. The contributions of various types of biological molecules to the total singlet oxygen quenching were calculated from their plasma concentrations and their quenching constants. Plasma proteins quenched most of the singlet oxygen. Uric acid also quenched a significant amount of singlet oxygen (12%). Tocopherols, carotenoids, ascorbic acid and bilirubin made only small contributions to the total singlet oxygen quenching (=s 4%). Copyright © 1990, Wiley Blackwell. All rights reserved