Reaction of HO. with Guanine Derivatives in Aqueous Solution: Formation of Two Different Redox-Active OH-Adduct Radicals and Their Unimolecular Transformation Reactions. Properties of G(-H).

Abstract

The reaction of .OH with 2′-deoxyguanosine yields two transient species G4.-OH and G8.-OH, which have strongly different reactivity towards O2 or other oxidants or to reductants. G8.-OH reacts with oxygen with k=4×109 M−1 s−1; in the absence of oxygen it undergoes a rapid ring-opening reaction (k=2×105 s−1; see scheme). Both G8.-OH and its ring-opened successor are one-electron reductants. In contrast, G4.-OH has oxidizing properties; it undergoes a slower transformation reaction (k=6×103 s−1) to produce the even more strongly oxidizing (deprotonated) 2′-deoxyguanosine radical cation.