PULSE-RADIOLYTIC INVESTIGATIONS OF CATECHOLS AND CATECHOLAMINES .2. REACTIONS OF TIRON WITH OXYGEN RADICAL SPECIES

Transient spectra and kinetic data of Tiron (1,2-dihydroxybenzene-3,5-disulphonic acid) are reported, obtained after pulse-radiolytic oxidation by hydroxyl radicals ({ring operator}OH), superoxide anions (O2-) or a combination of both oxygen radicals. The rate constant with {ring operator}OH radicals was determined at 1.0·109 M-1·s-1. Contrary to a previous report (Greenstock, C.L. and Miller, R.W. (1975) Biochim. Biophys. Acta 396, 11-16), the rate constant with O2- of 1.0·107 M-1·s-1 is lower by one order of magnitude; also the semiquinone absorbs at 300 nm rather than at 400 nm. The ratio of the rate constants with {ring operator}OH and O2- of 100 again demonstrates that any oxidation reaction by the latter radical is unspecific due to the more efficient reaction of {ring operator}OH radicals, leading to the same products with catechol compounds. © 1979.