期刊
MAGNETIC RESONANCE IN CHEMISTRY
卷 47, 期 12, 页码 1036-1042出版社
WILEY
DOI: 10.1002/mrc.2509
关键词
NMR; Na-23; H-1; G-quadruplex; alkali metal ions
资金
- Italian Ministry of University and Research (MIUR)
A comparative study of the competitive cation exchange between the alkali metal ions K+, Rb+, and Cs+ and the Na+ ions bound to the dimeric quadruplex [d(G(4)T(4)G(4))](2) Was performed in aqueous solution by a combined use of the Na-23 and H-1 NMR spectroscopy. The titration data confirm the different binding affinities of these ions for the G-quadruplex and, in particular, major differences in the behavior of Cs+ as compared to the other ions were found. Accordingly, Cs+ competes with Na+ only for the binding sites at the quadruplex surface (primarily phosphate groups), while K+ and Rb+ are also able to replace sodium ions located inside the quadruplex. Furthermore, the H-1 NMR results relative to the CsCl titration evidence a close approach of Cs+ ions to the phosphate groups in the narrow groove of [d(G(4)T(4)G(4))](2). Based on a three-site exchange model, the Na-23 NMR relaxation data lead to an estimate of the relative binding affinity of Cs+ versus Na+ for the quadruplex surface of 0.5 at 298 K. Comparing this value to those reported in the literature for the surface of the G-quadruplex formed by 5'-guanosinemonophosphate and for the surface of double-helical DNA suggests that topology factors may have an important influence on the cation affinity for the phosphate groups on DNA. Copyright (C) 2009 John Wiley & Sons, Ltd.
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