In this thesis, the concept of metal base-pairing was adapted for usage with the DNA secondary structure of G-quadruplexes. Apart from the well-known B-DNA double helix, oligonucleotides can form a variety of different topologies. G-quadruplexes self-assemble from guanine-rich DNA strands forming G-quartets, which stack on top of each other, and are believed to play an important biological role, e. g. during DNA transcription, replication and telomere maintenance. The unique folding behaviour of G-quadruplexes was used to establish a “metal base-tetrad” motif in analogy to the metal base-pairing concept developed for duplex DNA. The metal base-tetrad consists of four identical monodentate pyridine ligands, each covalently appended via an alkyl linker to a guanine-rich oligonucleotide strand, and a transition metal ion coordinating the ligands. Formation of the metal base-tetrad stabilises the respective G-quadruplex topology and is also able to trigger G-quadruplex formation. Characterisation was achieved by UV-VIS, CD, and EPR spectroscopy, ESI mass spectrometry, and gel electrophoresis. Three main results have been achieved. First, a simple but easily adaptable ligand synthesis was developed and the successful ligand incorporation into guanine-rich oligonucleotides was demonstrated. Second, stabilisation of tetramolecular G-quadruplexes, with even more than one instance of the metal base-tetrad could be achieved. Third, stabilisation and topology switching induced by transition metal ion coordination was shown for unimolecular G-quadruplexes.
Keywords: DNA nanotechnology; supramolecular chemistry; G-quadruplexes; Metal base-tetrad
