Reduction of β-phosphorylated cyclic aminoxyl radicals by flavins: an EPR kinetic study†

Abstract

A series of stable β-phosphorylated aminoxyl radicals has been tested towards their resistance to photoreduced flavin reduction in a pH 7.4 phosphate buffer. Their decay kinetics, monitored by EPR spectroscopy, have been compared to those of three non-phosphorylated reference compounds. In each case, both a second-order reduction and a first-order aminoxyl decay were found to contribute to the EPR signal loss. On the basis of only the second-order process, a classification of the aminoxyl radicals has been established as a function of their ease of reduction by the two flavins tested.