Disodium guanosine 5 '-monophosphate self-associates into nanoscale cylinders at pH 8: A combined diffusion NMR spectroscopy and dynamic light scattering study

作者：Wong A; Ida R; Spindler L; Wu G^*

来源：Journal of the American Chemical Society, 2005, 127(19): 6990-6998.

DOI：10.1021/ja042794d

We report a combined NMR and dynamic light scattering (DLS) study on the size of supramolecular structures formed by disodiurn 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 Na2(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 similar to 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 D2O than in H2O, whereas the size of monomer aggregates remains the same in D2O and in H2O. 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.

• 出版日期2005-5-18