A series of anthraquinone-linked DNA and DNA/RNA hybrid duplexes was prepared and examined to assess the effect of global structure on long-range charge transport. Spectroscopic and chemical evidence indicates that the DNA/RNA hybrid duplexes adopt an overall A-form-like structure. Irradiation of the covalently linked anthraquinone group injects a radical cation and leads to remote damage at GG steps, which is revealed as strand breaks by subsequent 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 interpreted within the phonon-assisted polaron-like hopping model to show that the reaction of a radical cation with H2O in the A-form helix is inhibited relative to this reaction in B-form DNA.
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