The article aims to present an electrochemical investigation of DNA heptamers d(GCNNNGC) with a different central trinucleotide sequence (NNN = GAA, AAA, CCC, and GGG, where A, C, and G is adenine, cytosine, and guanine, respectively). In phosphate-acetate buffer at pH 5.8 all heptamers were adsorbed on a hanging mercury electrode, and these adsorbed heptamers underwent reduction and oxidation. The voltammetric reduction peaks of A and C moiety and oxidation peaks of G moiety at different concentrations (0.25–10 µmol dm−3) were analyzed. It was found that the changes in the central trinucleotide sequence of the heptamers result in altered adsorption ability at a charged phase interface. An electron transfer process in an adsorptive state was evidenced by the elimination voltammetric procedure. For the evaluation of adsorption efficiency of the heptamers the Langmuir adsorption model was applied and the adsorption coefficient b was calculated.
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