Hexachloroiridate(IV) as a redox probe for the electrochemical discrimination of B-DNA and M-DNA monolayers on gold |
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Authors: | Michael J. Dinsmore Jeremy S. Lee |
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Affiliation: | aDepartment of Biochemistry, University of Saskatchewan, 107 Wiggins Road, Saskatoon, Canada S7N 5E5 |
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Abstract: | This paper demonstrates the effectiveness of using the redox couple to investigate DNA monolayers, and compares the potential advantages of this system to the standard redox couple. B-DNA monolayers were converted to M-DNA by incubation in buffer containing 0.4 mM Zn2+ at pH 8.6 and studied by cyclic voltammetry (CV), impedance spectroscopy (IS) and chronoamperometry (CA) with . Compared to B-DNA, M-DNA showed significant changes in CV, IS and CA spectra. However, only small changes were observed when the monolayers were incubated in Mg2+ at pH 8.6 or in Zn2+ at pH 6.0. The heterorgeneous electron-transfer rate (kET) between the redox probe and the surface of a bare gold electrode was determined to be 5.7 × 10−3 cm/s. For a B-DNA modified electrode, the kET through the monolayer was too slow to be measured. However, under M-DNA conditions, a kET of 1.5 × 10−3 cm/s was reached. As well, the percent change in resistance to charge transfer, measured by IS, was used to illustrate the dependence of M-DNA formation on pH. This result is consistent with Zn2+ ions replacing the imino protons on thymine and guanine residues. The redox couple was also effective in differentiating between single-stranded and double-stranded DNA during de-hybridization and rehybridization experiments. |
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Keywords: | Hexachloroiridate DNA monolayers Biosensors Electrochemical impedance spectroscopy M-DNA |
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