Rate constants of quenching of the fluorescence of pterins by the iodide anion in aqueous solution

The fluorescence of various pterins (6-methylpterin, 6-hydroxymethylpterin, 6-formylpterin, and 6-carboxypterin) was studied in the presence of iodide in neutral aerated phosphate buffer. Stern–Volmer plots and the fluorescence lifetimes were used to determine fluorescence quenching rate constants that approach the diffusion controlled limit. Given that pterin derivatives have been detected in human skin exposed to UV radiation, biological implications of the high rate constants are discussed.