Hydrogen Evolution Facilitates Reduction of DNA Guanine Residues at the Hanging Mercury Drop Electrode:Evidence for a Chemical Mechanism

Warning

This publication doesn't include Faculty of Medicine. It includes Central European Institute of Technology. Official publication website can be found on muni.cz.

Authors	DAŇHEL Aleš HAVRAN Luděk TRNKOVÁ Libuše FOJTA Miroslav
Year of publication	2016
Type	Article in Periodical
Magazine / Source	Electroanalysis
MU Faculty or unit	Central European Institute of Technology
Citation
Web	http://onlinelibrary.wiley.com/doi/10.1002/elan.201600242/full
Doi	http://dx.doi.org/10.1002/elan.201600242
Field	Analytic chemistry
Keywords	guanine; DANN; cisplatin; mercury electrode; catalytic hydrogen evolution; electrochemical reduction; chemical reduction; cyclic voltammetry
Description	Guanine (G), as well as G residues in nucleosides, nucleotides and nucleic acids, undergo chemically reversible (but electrochemically irreversible) reduction/oxidation processes at the mercury-based electrodes. It has been established that G is reduced to 7,8-dihydroguanine at highly negative potentials. The reduction product is oxidized back to G around -0.25V, giving rise to anodic peak G. Previous studies suggested involvement of a chemical mechanism involving electrochemically generated hydrogen radicals in the G reduction process. In this work we studied effects of cisplatin and pH on the G reduction process. We have found that catalytic hydrogen evolution accompanying electrochemical reduction of cisplatin markedly facilitates reduction of G. Minimum negative potential required for G reduction were shifted to less negative values and correlated with the onset of catalytic currents of cisplatin. Analogous shifts of the potential of G reduction were observed upon lowering pH of the background electrolyte (i.e., increasing the availability of protons to generate hydrogen radicals). Ammonium ions markedly increased efficiency of G reduction, which may be explained by generation of active hydrogen via formation and subsequent decomposition of ammonium amalgam. Our results strongly suggest that chemical mechanism(s) involving hydrogen radicals, electrochemically and/or electrocatalytically generated at the HMDE, contribute to the guanine 7,8-dihydroguanine conversion.