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Publication - Professor Mike Ashfold

    The Role of 1πσ* States in the Formation of Adenine Radical-Cations in DNA Duplexes


    Karsili, TNV, Marchetti, B & Ashfold, M, 2018, ‘The Role of 1πσ* States in the Formation of Adenine Radical-Cations in DNA Duplexes’. Chemical Physics, vol 515., pp. 464-471


    Photoinduced damage of DNA is a well-known but still far from fully understood phenomenon. Electronic structure methods are here employed to investigate potential roles of πσ states in initiating photodamage, and ways in which πσ-state driven photochemistry
    might evolve with increasing molecular complexity. The study starts
    with the bare 9H-adenine molecule and progresses through to a model
    double-helix DNA duplex in aqueous solution. Relative to the gas phase, aqueous solvation is predicted to stabilize the 1πσ
    states of these systems when exciting at the respective ground state
    equilibrium geometries, but to have relatively little effect on the
    asymptotic NH bond strengths. But the study also re-emphasises the potential importance of rival σ ← π excitations, wherein a solute π electron is promoted to a σ orbital localized on an OH bond of a complexing H2O molecule, as a route to forming parent radical cations – as have recently been observed following near UV photoexcitation of double-helix adenine-thymine duplexes in water (Banyasz et al., 2018). The subsequent deprotonation of such radical cations offers a rival low energy route to NH bond fission and radical formation in such duplexes.

    Full details in the University publications repository