Interaction of Viologens with Nucleic Acid G-Tetrades

The interaction between the tetrade-forming oligonucleotide 5′-d(T4G4T4) and monoalkylated bipyridinium salts, such as 1-ethyl-4-pyridin-4-ylpyridinium bromide, is reported. The oligomer forms tetrades in the presence of K+ ions but not with Li+. Additionally, the interaction of the thrombin-binding aptamer 5′-d(GGTTGGTGTGGTTGG) (TBA) with a dialkylated bipyridinium salt, viologen, was studied by cyclic voltammetry. This was performed either on a TiO2 electrode, derivatized with 3-aminopropyltriethoxysilane (APS), using [Fe(CN)6]4− as a marker ion or without a marker ion on an electrostatically TiO2-bound amino-ferrocenyl derivative. Both experiments proof a strong interaction between the immobilized aptamer and the viologen. Third, the electrochemical response of the specific thrombin binding to the immobilized aptamer was studied.