title: Disodium guanosine 5'-monophosphate self-associates into nanoscale cylinders at pH 8: a combined diffusion NMR spectroscopy and dynamic light scattering study.
abstract: We report a combined NMR and dynamic light scattering (DLS) study on the size of supramolecular structures formed by disodium guanosine 5'-monophosphate, Na(2)(5'-GMP), at pH 8. In general, two distinct types of aggregate species are present in an aqueous solution of Na(2)(5'-GMP). One type consists of stacking 5'-GMP monomers, and the other contains stacking G-quartets. Both types of aggregates can be modeled as rodlike cylinders. The cylinder diameter is 10 and 26 A for monomer aggregates and quartet aggregates, respectively. For Na(2)(5'-GMP) concentrations between 18 and 34 wt %, the cylinders formed by stacking G-quartets have an average length between 8 and 30 nm, corresponding to a stack of approximately 24-87 G-quartets. These nanoscale aggregates are significantly larger than what had previously been believed for Na(2)(5'-GMP) self-association at pH 8. The length of both types of 5'-GMP aggregates was found to increase with Na(2)(5'-GMP) concentration but was insensitive to the added NaCl in solution. While the aggregate size for monomer aggregates increases with a decrease in temperature, the size of G-quartet aggregates is essentially independent of temperature. We found that the size of G-quartet aggregates is slightly larger in D(2)O than in H(2)O, whereas the size of monomer aggregates remains the same in D(2)O and in H(2)O. We observed a linear relationship between the axial ratio of the 5'-GMP cylinders and the Na(2)(5'-GMP) concentration for both types of 5'-GMP aggregates, which suggests a common stacking mechanism for monomers and G-quartets.
authors.affiliation: Department of Chemistry, Queen's University, 90 Queen's Crescent, Kingston, Ontario, Canada K7L 3N6.
authors.forename: Alan
authors.initials: A
authors.lastname: Wong
authors.forename: Ramsey
authors.initials: R
authors.lastname: Ida
authors.forename: Lea
authors.initials: L
authors.lastname: Spindler
authors.forename: Gang
authors.initials: G
authors.lastname: Wu
mesh_terms: D004247:DNA / Q000737:chemistry; D006157:Guanosine Monophosphate / Q000031:analogs & derivatives* / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D008027:Light; D008958:Models, Molecular; D049329:Nanostructures / Q000737:chemistry*; D019906:Nuclear Magnetic Resonance, Biomolecular / Q000379:methods; D012542:Scattering, Radiation; D016615:Telomere / Q000235:genetics; D013696:Temperature; D013816:Thermodynamics
chemical_list: D006157:Guanosine Monophosphate; D004247:DNA