Exploiting the interaction of metal ions and peptide nucleic acids-DNA duplexes for the detection of a single nucleotide mismatch by electrochemical impedance spectroscopy.

The interaction of the metal ions Mg(2+), Zn(2+), Ni(2+), and Co(2+) with DNA-peptide nucleic acid (PNA) films on a gold surface is studied by electrochemical impedance spectroscopy in the presence of Fe(CN)(6) as the redox probe. Impedance data were analyzed with the help of a modified Randles' equivalent circuit. Changes in the charge-transfer resistance, R(CT), decreases in the order of Ni(2+) > Co(2+) > Zn(2+) > Mg(2+). We interpret these results in terms of stronger interactions for Ni(2+) with the DNA-PNA film compared to the other metal ions, potentially involving interactions with the nucleobases, presumably with the N7 of purines or the N3 of pyrimidines. On the basis of these observations, Ni(2+) was chosen to probe the detection of a C-T mismatch in 15-mer PNA-DNA films. Using Ni(2+), it is possible to detect a single C-T mismatch. The resulting DeltaR(CT) is larger for the PNA-DNA hybrid compared to that for the identical 15-mer DNA-DNA hybrid.