Role of azide concentration in pulse radiolysis studies of oxidation: 3,4-dihydroxyphenylalanine

Abstract

The radiolysis of aqueous solutions of 3,4-dihydroxyphenylalanine (dopa) using N^˙₃ as a one-electron oxidant leads to the formation of dopasemiquinone and, successively, dopaquinone and dopachrome. It is now shown that under pH conditions where significant protonation of N^–₃ to HN₃ occurs, dopachrome formation is suppressed, probably due predominantly to addition of HN₃ to dopaquinone. The possibility of such nucleophilic reactions occurring needs to be considered in studies of quinone intermediates generated using N^–₃ as oxidant.