Kinetics and spectral properties of electron adducts of 2'-deoxyinosine: a comparison with other purine nucleosides

Abstract

The heteroatom-protonated electron adducts of 2'-deoxyinosine formed following rapid protonation of the initially-produced radical anions in neutral solution exhibit a broad peak around 310 nm. In neutral solutions, these radicals transform spontaneously, in a slow process (k~2 × 10⁴ s^-1), into C-protonated adducts. This reaction is catalysed by OH^- and the absorption changes at 350 nm vs. pH consist of two types of pK_a curve. The transformation rates in 2'-deoxyinosine are somewhat higher than those found for inosine and are in accord with the yields of MV^•+. The spectrum at pH ≥ 13.5 closely resembles the H-adduct spectrum recorded at neutral pH. This spectrum with ε ₃₁₅= 5900 and ε ₃₅₀= 4400 dm³ mol^-1 cm^-1 is assigned to the C-8 protonated adducts. This study suggests that the heteroatomprotonated and C-2 protonated electron adducts of 2'-deoxyinosine are probably less stable than the corresponding radicals of inosine.