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We herein explore a novel route for oxidative stress in DNA by using electrochemistry as mimicking tool. Essentially, the electrochemical oxidation of guanine and adenine nucleosides and oligo-homo-nucleotides at pyrolytic graphite electrodes in neutral and alkaline aqueous solutions was studied. Under these experimental conditions all these compounds give rise to an adsorbed product not previously described, which was electrochemically and kinetically characterized. The virtually identical kinetic and electrochemical features exhibited by the oxidized compounds generated from all precursors strongly suggest a common species arising from both adenine and guanine derivatives. Supported by DFT calculations, we propose two convergent pathways for the electrochemical oxidation of adenosine and guanosine. Those calculations indicate that the common oxidized base product forms stable H-bond base pairs with both thymine and cytosine. Keywords: Cyclic voltammetry, Density functional calculations, Electrochemistry, Guanosine, Substitution mutation

A new electrocatalytic scheme for the detection of DNA is described. This scheme relies on the different interactions of single- and double-stranded oligonucleotides with the organic dyes methylene blue, thionin, azure A, azure B, toluidine blue O, brilliant cresyl blue and neutral red, which in addition can act as NADH catalysts. This catalytic activity can be used for amplifying differentiation between duplex and single-stranded DNA. Pyrolytic graphite electrodes modified with adsorbed dsDNA–organic dye complexes gave higher electrocatalytic NADH oxidation currents than those measured with electrodes modified with adsorbed ssDNA–organic dye. This difference is maximum for brilliant cresyl blue. These results suggest that the proposed scheme may be useful for the detection of DNA hybridisation and damage. Keywords: DNA hybridisation, Catalytic NADH oxidation, Phenoxazines, Phenothiazines, Phenazines