DNA and RNA sequences, specifically guanine-rich oligonucleotides (GROs), readily adopt quadruple helical structures due to the association of guanine bases forming G-quartets. Recent discoveries indicate G-quadruplex structures (GQs) are significantly involved with information metabolism. G-DNA structures occur in a variety of locations in chromosomes, such as the promoter regions, telomeric regions, and replication origin sequences. Certain GROs resembling G-DNA forming repeat motifs can self-assemble into supramolecular configurations called G-wires. G-wires readily self-assemble in the presence of specific monovalent and divalent cations to produce stable polydisperse linear structures. G-wires have been used as a scaffold for aligning gold nanoparticles, though complete potential biological activity is mostly unknown. This work investigates a strategy for limiting the polydispersity of simple G-wire forming GROs as proof of concept for controlling self-assembly. The GROs used in this work were 5’-dGGGGG-3’(GRO7), 5’-dTGGGGG-3’ (GRO8a), and 5’-dGGGGGT-3’ (GRO8b). The sequence composition of these GROs consequently varied in their G-wire formation. The parallel G-DNA specific fluorescent dye, N-methylmesoporphoryn (NMM) at varying concentrations to attenuate G-wire self-assembly. The attenuation is likely due to NMM’s affinity for binding to the 3’ end of the G-wire, effectively “capping” further association of GQs. Analysis of NMM attenuated G-wire assemblies by polyacrylamide gel electrophoresis (PAGE) shows a shortening of G-wire size. The extent of attenuation is dependent on the NMM:GRO ratio and the type of cation used for self-assembly. At saturating concentrations of NMM, the presence of a presumed G-DNA supramolecular repeat monomer and dimer were observed. Based on PAGE attenuation experiments, we hypothesize a 5’-Head to 3’-Tail (HTT) stacking association of supramolecular monomer G-DNAs that NMM competes for 3’-tail binding. The putative dimer may be due to HTH (5’-5’) stacking association. We plan to investigate the HTH and HTT stacking hypothesis using mass spectroscopy. This will contribute valuable knowledge of the use of G-wires in possible bio/nano material applications such as nanoelectronics, immortal cell treatment, and supramolecular scaffold material in biological systems. Understanding the details of G-wire formation are key to accessing these potential fields.

Attenuation of G-wire self-assembly using G-quadruplex ligands

2019 Spring National Meeting

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.