Kinetic and Thermodynamic Hysteresis Imposed by Intercalation of Proflavine in Ferrocene-Modified Double-Stranded DNA

Authors

  • Dr. Magdalena Gebala,

    Corresponding author
    1. Analytische Chemie—Elektroanalytik & Sensorik, Ruhr-Universität Bochum, Universitätsstr. 150, D-44780 Bochum (Germany), Fax: (+49) 234 3214683 www.rub.de/elan
    2. Current address: Stanford School of Medicine, Dept. Biochemistry, Beckman Center, B400, 279 W. Campus Dr. MC: 5307, Stanford, CA 94305 (USA)
    • Analytische Chemie—Elektroanalytik & Sensorik, Ruhr-Universität Bochum, Universitätsstr. 150, D-44780 Bochum (Germany), Fax: (+49) 234 3214683 www.rub.de/elan

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  • Dr. Fabio La Mantia,

    1. Center for Electrochemical Sciences—CES, Ruhr-Universität Bochum, Universitätsstr. 150, D-44780 Bochum (Germany)
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  • Prof. Dr. Wolfgang Schuhmann

    1. Analytische Chemie—Elektroanalytik & Sensorik, Ruhr-Universität Bochum, Universitätsstr. 150, D-44780 Bochum (Germany), Fax: (+49) 234 3214683 www.rub.de/elan
    2. Center for Electrochemical Sciences—CES, Ruhr-Universität Bochum, Universitätsstr. 150, D-44780 Bochum (Germany)
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Abstract

Surface-confined immobilized redox species often do not show the expected zero peak separation in slow-scan cyclic voltammograms. This phenomenon is frequently associated to experimental drawbacks and hence neglected. However, a nonzero peak separation, which is common to many electrochemical systems with high structural flexibility, can be rationally assigned to a thermodynamic hysteresis. To study this phenomenon, a surface-confined redox species was used. Specifically, a DNA strand which is tagged with ferrocene (Fc) moieties at its 5′ end and its complementary capture probe is thiolated at the 3′ end was self-assembled in a monolayer at a Au electrode with the Fc moieties being located at the bottom plane of the double-stranded DNA (dsDNA). The DNA-bound Fc undergoes rapid electron transfer with the electrode surface as evaluated by fast scan cyclic voltammetry. The electron transfer is sensitive to the ion transport along the DNA strands, a phenomenon which is modulated upon specific intercalation of proflavine into surface-bound dsDNA. The electron transfer rate of the Fc0/+ redox process is influenced by the cationic permselectivity of the DNA monolayer. In addition to the kinetic hindrance, a thermodynamic effect correlated with changes in the activity coefficients of the Fc0/+ moieties near the gold-dsDNA interface is observed and discussed as source of the observed hysteresis causing the non-zero peak separation in the voltammograms.

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