title: Kinetic and thermodynamic hysteresis imposed by intercalation of proflavine in ferrocene-modified double-stranded DNA.
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 Fc(0/+) 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 Fc(0/+) 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.
authors.affiliation: Analytische Chemie-Elektroanalytik & Sensorik, Ruhr-Universität Bochum, Universitätsstr. 150, D-44780 Bochum, Germany. magdalena.gebala@rub.de
authors.forename: Magdalena
authors.initials: M
authors.lastname: Gebala
authors.forename: Fabio
authors.initials: F
authors.lastname: La Mantia
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Schuhmann
mesh_terms: D004247:DNA / Q000737:chemistry*; D005296:Ferrous Compounds / Q000737:chemistry*; D007700:Kinetics; D000075163:Metallocenes; D011370:Proflavine / Q000737:chemistry*; D013816:Thermodynamics
chemical_list: D005296:Ferrous Compounds; D000075163:Metallocenes; D004247:DNA; D011370:Proflavine; C004998:ferrocene
keywords: DNA; cyclic voltammetry; electron transfer; ferrocene; intercalation