Electrochemically Induced Oxidative Damage to Double-Stranded Calf Thymus DNA Adsorbed on Gold Electrodes

E. E. Ferapontova^1* and S. V. Shipovskov²

¹Department of Analytical Chemistry, Lund University, P.O. Box 124, SE-221 00, Lund, Sweden; fax: +4646222 44544; E-mail: ferapontova@hotmail.com; elena.ferapontova@analykem.lu.se

²Department of Chemical Enzymology, School of Chemistry, Lomonosov Moscow State University, Moscow, 119899 Russia; E-mail: stepa@enzyme.chem.msu.ru

^* To whom correspondence should be addressed.

Received December 1, 2001; Revision received May 5, 2002

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Electrochemically induced oxidative damage to DNA was studied with double-stranded calf thymus DNA immobilized directly on a gold electrode surface. Pre-polarization of the DNA-modified electrodes at +0.5 V versus Ag/AgCl reference electrode, in a free from DNA blank buffer solution, pH 7.4, allowed for subsequent detection of direct electrochemical oxidation of adsorbed on gold DNA, in the potential range from +0.7 to +0.8 V. The redox potential of the process corresponded to the potentials of the oxidation of guanine bases in DNA. It is shown that with increasing potential scan rate, v, the mechanism of electrochemical oxidation of DNA changes from the irreversible 4e^- oxidative damage of DNA at low v to reversible 1e^- oxidation at high v, keeping the electrochemical activity of the adsorbed DNA layer virtually the same.

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KEY WORDS: oxidative DNA damage, guanine, gold electrode

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