Generation of hydroxyl radical by photolysis of mercaptopyridine N-oxides: Application to redox chemistry of purines

This chapter discusses generation of hydroxyl radical (OH') by photolysis of mercaptopyridine n-oxides: application to redox chemistry of purines. The classical method to generate the OH' radical in vitro is the radiolysis of water using, for instance, γ rays or high energy electrons. However, the use of nonradiolytic methods has shown to be a convenient way to produce OH' and simulate the indirect effect of ionizing radiation on living systems. These so-called “radiomimetic” methods include Fenton-type chemical reactions and photolysis of hydrogen peroxide and N-oxides of mercaptopyridines. Within this latter class of compounds, 4-mercaptopyridine N-oxide has proven to be an especially effective generator of OH'. The chapter illustrates this method by studying the radical redox chemistry of some biologically relevant purines, by characterizing the transient radicals by electron paramagnetic resonance (EPR) spectroscopy and identifying the final stable products by high-performance liquid chromatography (HPLC).