Molecular mechanism of base pairing infidelity during DNA duplication upon one-electron oxidation

Abstract

The guanine radical cation (G •+ ) is formed by one-electron oxidation from its parent guanine (G). G•+ is rapidly deprotonated in the aqueous phase resulting in the formation of the neutral guanine radical [G (-H) • ]. The loss of proton occurs at the N1 nitrogen, which is involved in the classical Watson-Crick base pairing with cytosine (C). Employing the density functional theory (DFT), it has been observed that a new shifted base pairing configuration is formed between G(-H)• and C constituting only two hydrogen bonds after deprotonation occurs. Using the DFT method, G(-H)• was paired with thymine (T), adenine (A) and G revealing substantial binding energies comparable to those of classical G-C and A-T base pairs. Hence, G (-H) • does not display any particular specificity for C compared to the other bases. Taking into account the long lifetime of the G (-H) • radical in the DNA helix (5 s) and the rapid duplication rate of DNA during mitosis/meiosis (5-500 bases per s), G(-H)

Electrochemistry of deoxyribonucleic acid–cetyltrimethylammonium complex with considering O2 effect

“…When O 2 is excluded from the CH 2 Cl 2 electrolyte, G is electrochemically oxidized as radical cation 1 [47], which is presented in Scheme 1. It is noted that the oxidation potential of DNA-CTMA under N 2 is nearly the same as that under O 2 in aqueous NaOH electrolyte, where the deprotonation and oxidation by oxygen of G in NaOH can also produce radical 3 which is oxidized at the potential of 0.5 V. [48][49][50] Based on the experimental results, we propose that the resonance structure of G, 2 which has the delocalized electron over the base is sensitive to the O 2 oxidation.…”