Characterization of the Cation and Temperature Dependence of DNA Quadruplex Hydrogen Bond Properties Using High-Resolution NMR

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• 作者：Andrew J. Dingley ; Robert D. Peterson ; Stephan Grzesiek ; and Juli Feigon
• 刊名：Journal of the American Chemical Society
• 出版年：2005
• 出版时间：October 19, 2005
• 年：2005
• 卷：127
• 期：41
• 页码：14466 - 14472
• 全文大小：291K
• 年卷期：v.127,no.41(October 19, 2005)
• ISSN：1520-5126

文摘

Variations in the hydrogen bond network of the Oxy-1.5 DNA guanine quadruplex have beenmonitored by trans-H-bond scalar couplings, ^h2J_N2N7, for Na⁺-, K⁺-, and NH₄⁺-bound forms over a temperaturerange from 5 to 55 C. The variations in ^h2J_N2N7 couplings exhibit an overall trend of Na⁺ > K⁺ > NH₄⁺ andcorrelate with the different cation positions and N2-H2···N7 H-bond lengths in the respective structures.A global weakening of the ^h2J_N2N7 couplings with increasing temperature for the three DNA quadruplexspecies is accompanied by a global increase of the acceptor ¹⁵N7 chemical shifts. Above 35 C, spectralheterogeneity indicates thermal denaturation for the Na⁺-bound form, whereas spectral homogeneity persistsup to 55 C for the K⁺- and NH₄⁺-coordinated forms. The average relative change of the ^h2J_N2N7 couplingsamounts to ~0.8 × 10^-3/K and is thus considerably smaller than respective values reported for nucleicacid duplexes. The significantly higher thermal stability of H-bond geometries in the DNA quadruplexescan be rationalized by their cation coordination of the G-quartets and the extensive H-bond network betweenthe four strands. A detailed analysis of individual ^h2J_N2N7 couplings reveals that the 5' strand end, comprisingbase pairs G1-G9* and G4*-G1, is the most thermolabile region of the DNA quadruplex in all three cation-bound forms.