Application of the new EPR spin trap 1,1,3-trimethylisoindole N-oxide (TMINO) in trapping HO. and related biologically important radicals

The new EPR spin trap, 1,1,3-trimethylisoindole N-oxide (TMINO), very efficiently scavenges several Fenton-derived carbon- and oxygen-centred radicals including hydroxyl, formyl and alkyl radicals. The adducts display good stability and narrow EPR line-widths, allowing the detection of the expected radicals as well as two-dimensional (time-resolved) EPR experiments. Trapping experiments were also undertaken with superoxide radicals (giving no EPR signals) and nitric oxide (which gave strong EPR signals attributed to the action of higher oxides of nitrogen). The selectivity of TMINO towards HO. with respect to superoxide radicals demonstrates its potential as a useful spin-trap.