Single-electron transfer from NADH analogues to singlet oxygen.

Laser flash photolysis techniques have yielded rate constants for physical and reactive quenching modes of O2(1 delta g) by nicotine, nicotinamide adenine dinucleotide (oxidized and reduced forms) and the reduced forms of nicotinamide mononucleotide, nicotinamide adenine dinucleotide phosphate and nicotinamide hypoxanthine dinucleotide. In the case of the last four named compounds, kinetic spectroscopy furnished evidence for one-electron transfers to O2(1 delta g). Specifically, production of O2 was demonstrated unequivocally by reaction with 1,4-benzoquinone. Quantitative determinations revealed the extent of reactive quenching to be near 60% in each case.