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Issue 19, 2018
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Mechanistic insights into the photogeneration and quenching of guanine radical cation via one-electron oxidation of G-quadruplex DNA

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Abstract

Herein, mechanistic aspects of the photogeneration and quenching of guanine radical cation through one-electron oxidation of the G-quadruplex of G2T2G2TGTG2T2G2 (TBA) sequence were investigated by a combined quantum mechanical/molecular mechanical (QM/MM) approach at the CASPT2//CASSCF/AMBER level of theory. Herein, one electron promotion of the oxygen lone pair of the photo-excited photosensitizer peroxydisulfate to its O–O σ* orbital was first demonstrated to become tunable through the varied reduction ability of the G base in the presence or absence of interbase hydrogen bonding, thereby dynamically controlling the deprotonation site in G-quadruplex TBA. The quenching of G radical cation mediated by the formation of SO42−via photoinduced electron transfer can be triggered effectively by the deprotonation reaction of free proton rather than that of the hydrogen-bonded proton in G–G (G-quartet) and G–T (loop) aqueous surrounding. By calculating the deprotonation paths for the G radical cation, the deprotonation reactions in G-quadruplex TBA were verified to proceed predominantly along the site of imino proton (N1–H) in the loop moiety; this showed the coexisting occurrence of amino (N2–H) deprotonation in the G-quartet part. The mechanistic features discussed in this study represent significant advances in the understanding of DNA radical chemistry.

Graphical abstract: Mechanistic insights into the photogeneration and quenching of guanine radical cation via one-electron oxidation of G-quadruplex DNA

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Publication details

The article was received on 16 Mar 2018, accepted on 23 Apr 2018 and first published on 24 Apr 2018


Article type: Paper
DOI: 10.1039/C8CP01718B
Citation: Phys. Chem. Chem. Phys., 2018,20, 13598-13606
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    Mechanistic insights into the photogeneration and quenching of guanine radical cation via one-electron oxidation of G-quadruplex DNA

    Y. Yang, W. Yang, H. Su, W. Fang and X. Chen, Phys. Chem. Chem. Phys., 2018, 20, 13598
    DOI: 10.1039/C8CP01718B

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