Study of thermal and acid denaturation of DNA by means of voltammetry at graphite electrodes

Conformational changes in guanine–cytosine (G·C) and adenine–thymine (A·T) pairs in DNA were investigated by means of differential pulse voltammetry at a pyrolytic graphite electrode (PGE). As a monitor of these conformational changes, two separated voltammetric peaks, G and A, which correspond to electrochemical oxidation at the PGE of guanine and adenine residues, respectively, were used. It was found that peak A was first increased in the course of thermal denaturation of DNA. This indicates that, on heating a native DNA sample, regions rich in A·T pairs melt first. In the course of acid denaturation of a native DNA sample, the height of peak A was changed just before the denaturation. It is suggested that protonation of adenine residues in DNA regions rich in A·T pairs was responsible for these changes.