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Issue 21, 2018
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Direct observation of the oxidation of DNA bases by phosphate radicals formed under radiation: a model of the backbone-to-base hole transfer

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Abstract

In irradiated DNA, by the base-to-base and backbone-to-base hole transfer processes, the hole (i.e., the unpaired spin) localizes on the most electropositive base, guanine. Phosphate radicals formed via ionization events in the DNA-backbone must play an important role in the backbone-to-base hole transfer process. However, earlier studies on irradiated hydrated DNA, on irradiated DNA-models in frozen aqueous solution and in neat dimethyl phosphate showed the formation of carbon-centered radicals and not phosphate radicals. Therefore, to model the backbone-to-base hole transfer process, we report picosecond pulse radiolysis studies of the reactions between H2PO4˙ with the DNA bases – G, A, T, and C in 6 M H3PO4 at 22 °C. The time-resolved observations show that in 6 M H3PO4, H2PO4˙ causes the one-electron oxidation of adenine, guanine and thymine, by forming the cation radicals via a single electron transfer (SET) process; however, the rate constant of the reaction of H2PO4˙ with cytosine is too low (<107 L mol−1 s−1) to be measured. The rates of these reactions are influenced by the protonation states and the reorganization energies of the base radicals and of the phosphate radical in 6 M H3PO4.

Graphical abstract: Direct observation of the oxidation of DNA bases by phosphate radicals formed under radiation: a model of the backbone-to-base hole transfer

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Publication details

The article was received on 16 Jan 2018, accepted on 24 Apr 2018 and first published on 25 Apr 2018


Article type: Paper
DOI: 10.1039/C8CP00352A
Citation: Phys. Chem. Chem. Phys., 2018,20, 14927-14937
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    Direct observation of the oxidation of DNA bases by phosphate radicals formed under radiation: a model of the backbone-to-base hole transfer

    J. Ma, J. Marignier, P. Pernot, C. Houée-Levin, A. Kumar, M. D. Sevilla, A. Adhikary and M. Mostafavi, Phys. Chem. Chem. Phys., 2018, 20, 14927
    DOI: 10.1039/C8CP00352A

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