π–π stacked DNA G-wire nanostructures formed by a short G-rich oligonucleotide containing a 3′–3′ inversion of polarity site

The interest in DNA based nanostructures arises from their potential applications in diagnostics and drug delivery and in the development of new hybrid and conducting materials. Guanine-rich oligonucleotides can multimerize forming long and stable supramolecular structures, known as G-wires, based on the G-quadruplex (G4) motif. Herein, we report a method to easily obtain long DNA G-wires based on a new tetramolecular G4 subunit formed by the d(5′-CGG-3′-3′-GGC-5′) sequence containing a 3′–3′ inversion of polarity site. The formation of the G-wire assembly exploits the multimerization ability of G4s presenting the CGG motif at their 5′ end via π–π stacking interactions between flanking G4 subunits. The structures and the stability of the resulting G-wires were investigated by HPLC, size exclusion chromatography, polyacrylamide gel electrophoresis, circular dichroism, 1H NMR and atomic force microscopy studies.