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 ε₃₁₅= 5900 and ε₃₅₀= 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.