Time-dependent polyguanylic acid structural modifications

• Poly(G) single-strand is present only in freshly prepared solutions.
• Poly(G) single-strand self-assembles into G-quadruplex poly(G) configurations.
• Poly(G) adsorption morphology and redox behaviour are influenced by Na+ and K+ ions.
• G-quadruplex poly(G) redox behaviour shows incubation time dependence.

Polyguanylic acid (poly(G)) structural modifications are dependent on the presence of K+ or Na+ ions and incubation time, and were studied using atomic force microscopy (AFM) at a highly oriented pyrolytic graphite (HOPG) and voltammetry at a glassy carbon electrode. AFM images showed the poly(G) single-strand self-assembling into short G-quadruplex (GQ) regions after low incubation time, while large GQ poly(G) morphology aggregates with low adsorption were formed after high incubation times, decreasing the HOPG surface coverage. The voltammetry in freshly prepared poly(G) solutions showed the occurrence of the guanine (G) residues oxidation peak in the poly(G) single-strand. Increasing the incubation time, the G oxidation peak decreased and disappeared, and a GQ residues oxidation peak in the GQ poly(G) morphology appeared, at a higher oxidation potential, dependent on the incubation time, presenting a maximum after 10 days of incubation, and reaching a steady value after ~ 17 days of incubation.