Radical cation transport and reaction in RNA/DNA hybrid duplexes: Effect of global structure on reactivity

A series of anthraquinone-linked DNA and DNA/RNA hybrid duplexes was prepar ed and examined to assess the effect of global structure on long-range char ge transport. Spectroscopic and chemical evidence indicates that the DNA/RN A hybrid duplexes adopt an overall A-form-Like structure. Irradiation of th e covalently linked anthraquinone group injects a radical cation and leads to remote damage at GG steps, which is revealed as strand breaks by subsequ ent treatment with piperidine. Radical cation transport through the A-form hybrid duplex occurs, but the strand cleavage at GG steps in the hybrid is much less efficient than it is in duplex DNA. These findings are interprete d within the phonon-assisted polaron-like hopping model to show that the re action of a radical cation with H2O in the A-form helix is inhibited relati ve to this reaction in B-form DNA.