The effect of pH on the interaction between Eu3+ ions and short single-stranded DNA sequence, studied with electrochemical, spectroscopic and computational methods

For the first time, interaction of short single-stranded DNA (ssDNA) sequence with Eu3+ was studied by cyclic voltammetry (CV), differential pulse voltammetry (DPV) and UV–vis spectroscopy. The results show that interaction between Eu3+ ions and ssDNA is related to solution pH and pKa of ssDNA bases and have different binding mode at different pHs. It's clear that, at pH 3.7, only phosphate groups of ssDNA can interact with Eu3+ ions, because in this pH ssDNA bases are totally protonated. But at higher pH (5.5), some of ssDNA bases can interact with Eu3+ ions, too. Computational studies were done and confirm the result of experimental data. The agreement mutually verifies the accuracy of the methods. - Highlights: ► For the first time the electrochemical behavior of Eu3+ was investigated. ► The interaction of Eu3+ ion with a ssDNA was studied. ► The results showed Eu3+ binds to ssDNA mainly by electrostatic binding at pH 3.7. ► At higher pH (> 5.5) the nucleotide bases also contribute in the interaction.