Simultaneous determination of guanine and adenine contents in DNA, RNA and synthetic oligonucleotides using a chemically modified electrode

Abstract

Simultaneous determination of guanine and adenine contents in DNA, RNA and synthetic oligonucleotides on a Nafion–ruthenium oxide pyrochlore modified electrode is described. This chemically modified electrode shows very pronounced electrocatalytic effects towards the oxidation of guanine and adenine. The experimental parameters for individual determinations of guanine and adenine on the modified electrode were first optimised. Excellent detection limits (S/N = 3) of 0.86 ng ml^–1 (5.7 nM) and 2.7 ng ml^–1 (20 nM) for guanine and adenine, respectively, were obtained. Simultaneous determination of guanine and adenine in a mixture was also optimised. The denatured calf thymus DNA and yeast RNA showed oxidation peaks corresponding to guanine and adenine with a linear calibration line up to 5 µg ml^–1 in pH 4.0 phosphate buffer. The detection limit estimated for these nucleic acids were 11.5 ng ml^–1 and 37.7 ng ml^–1 for guanine and adenine, respectively. The new method provides an alternative to estimate the guanine and adenine contents more selectively and sensitively than currently applied techniques.