Electrochemical and Spectrometric Studies of Double-Strand Calf Thymus Gland DNA Denatured by Al(III) at Neutral pH

Abstract

The interaction between double-strand calf thymus gland DNA (ds-DNA) and Al(III) was studied by using differential pulse voltammetry (DPV) at a hanging mercury drop electrode (HMDE), Raman spectrometry and circular dichroism (CD) spectra. It was shown that at neutral pH ds-DNA did not produce any cathodic peak at the HMDE in the potential window from −550 to −2000 mV vs. SCE. However, in the presence of Al(III), a cathodic peak was generated at about −1660 mV, which is ascribed to a reduction of adenine and cytosine residues of single denatured DNA (sd-DNA). It was concluded that ds-DNA was completely denatured to sd-DNA by Al(III) at a neutral pH. The apparent denaturing kinetic velocity constants of ds-DNA by Al(III) were derived from linear increases of the cathodic peak currents with time. When [Al(III)]×[OH⁻]³ ≥ 2 × 10⁻²⁶, the precipitation of Al(OH)₃ was observed and identified by the Raman spectrum, and inductively coupled plasma atomic emission spectrometry (ICP-AES). CD spectra showed that the B-type of structure conformations of ds-DNA and related sd-DNA did not change with the increment of Al(III) from 5.0 × 10⁻⁷ to 1.0 × 10⁻⁵ M, but the corresponding absorption strengths increased. The related physiological significances and possible applications of the observations were considered.