In situ infrared spectroelectrochemical studies on adsorption and oxidation of nucleic acids at glassy carbon electrode

The adsorption and oxidation of yeast RNA and herring sperm DNA (HS DNA) at glass carbon (GC) electrode are studied by differential pulse voltammetry (DPV) and in situ FTIR spectroelectrochemistry. Two oxidation peaks of yeas t RNA are obtained by DPV, whose peak potentials shift negatively with incr easing pH. The peak currents decrease gradually in successive scans and no corresponding reduction peaks occur, thus indicating that the oxidation pro cess of yeast RNA is completely irreversible. The IR bands in the 1200-1800 cm-l range, attributed to the stretching and ring vibrations of nucleic ac id bases, show the main spectral changes when the potential is shifted posi tively, which gives evidence that the oxidation process takes place in the base residues. The oxidation process of HS DNA is similar to that of yeast RNA. The results both from DPV and in situ FTIR spectroelectrochemistry con firm that the guanine and adenine residues can be oxidized at the electrode surface, which is consistent with the oxidation mechanism of nucleic acids proposed previously. (C) 2001 Elsevier Science B.V. All rights reserved.