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  • Sequential electron transfe...
    Szabla, Rafał; Kruse, Holger; Stadlbauer, Petr; Šponer, Jiří; Sobolewski, Andrzej L.

    Chemical science (Cambridge), 02/2018, Letnik: 9, Številka: 12
    Journal Article

    QM/MM simulations elucidate the self-repair mechanism of the cyclobutane pyrimidine dimer. Cyclobutane pyrimidine dimers (CpDs) are among the most common DNA lesions occurring due to the interaction with ultraviolet light. While photolyases have been well known as external factors repairing CpDs, the intrinsic self-repairing capabilities of the GAT Created by potrace 1.16, written by Peter Selinger 2001-2019 T DNA sequence were discovered only recently and are still largely obscure. Here, we elucidate the mechanistic details of this self-repair process by means of MD simulations and QM/MM computations involving the algebraic diagrammatic construction to the second order ADC(2) method. We show that local UV-excitation of guanine may be followed by up to three subsequent electron transfers, which may eventually enable efficient CpD ring opening when the negative charge resides on the T Created by potrace 1.16, written by Peter Selinger 2001-2019 T dimer. Consequently, the molecular mechanism of GAT Created by potrace 1.16, written by Peter Selinger 2001-2019 T self-repair can be envisaged as sequential electron transfer (SET) occurring downhill along the slope of the S 1 potential energy surface. Even though the general features of the SET mechanism are retained in both of the studied stacked conformers, our optimizations of different S 1 /S 0 state crossings revealed minor differences which could influence their self-repair efficiencies. We expect that such assessment of the availability and efficiency of the SET process in other DNA oligomers could hint towards other sequences exhibiting similar photochemical properties. Such explorations will be particularly fascinating in the context of the origins of biomolecules on Earth, owing to the lack of external repairing factors in the Archean age.