Cation-dependence of the self-association behavior of guanylyl-(3'-5')-guanosine

• Published in: Journal of biomolecular structure & dynamics Vol. 10; no. 3; p. 619
• Main Authors: Walmsley, J A, Schneider, M L, Farmer, P J, Cave, J R, Toth, C R, Wilson, R M
• Format: Journal Article
• Language: English
• Published: England 01.12.1992
• Subjects: Cations, Monovalent - chemistry; Chromatography, Ion Exchange; Dinucleoside Phosphates - chemistry; Hydrogen Bonding; Magnetic Resonance Spectroscopy; Quaternary Ammonium Compounds - chemistry
• ISSN: 0739-1102; 1538-0254
• DOI: 10.1080/07391102.1992.10508672

The aggregation behavior of guanylyl-(3'-5')-guanosine, GpG, in the form of the tetramethylammonium (TMA), Li, Na, and K salts in aqueous solution has been investigated by NMR and FTIR techniques. The salts were prepared by a cation-exchange method. The ability of the cations to induce aggregate formation is TMA+ < Li+ < Na+ < K+, where TMA+ has only a weakly promoting action and K+ has a very strong effect. Three types of aggregates have been observed: (a) small aggregates which are in rapid exchange with respect to the NMR time scale; (b) intermediate-sized aggregates which are slow to exchange; (c) very large aggregates which can only be observed by FTIR. In all cases the aggregated species are held together by base stacking and guanine-guanine hydrogen bonding. A stoichiometry of 2 GpG per K+ has been determined by a 1H NMR titration of TMAGpG with KCl. Models have been proposed for the various-sized species. These include stacked dimers, stacked tetramers (similar to G-tetrads), and species in which K+ ion bridges between phosphates in separate tetramers.