On the Intrinsically Low Quantum Yields of Pyrimidine DNA Photodamages: Evaluating the Reactivity of the Corresponding Minimum Energy Crossing Points

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2020
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Abstract
The low quantum yield of photoformation of cyclobutane pyrimidine dimers and pyrimidine- pyrimidone (6−4) adducts in DNA bases is usually associated with the presence of more favorable non-reactive decay paths and with the unlikeliness of exciting the system in a favorable conformation. Here we prove that the ability of the reactive conical intersection to bring the system either back to the absorbing conformation or to the photoproduct must be considered as a fundamental factor in the low quantum yields of the mentioned photodamages. In support of the proposed model, the one order of magnitude difference in the quantum yield of formation of the cyclobutane thymine dimer with respect to the thymine-thymine (6-4) adduct is rationalized here by comparing the reactive ability of the corresponding seam of intersections at the CASPT2 level of theory.
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Giussani, Angelo Worth, Graham A. 2020 On the Intrinsically Low Quantum Yields of Pyrimidine DNA Photodamages: Evaluating the Reactivity of the Corresponding Minimum Energy Crossing Points Journal Of Physical Chemistry Letters 11 13 4984 4989
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