NMR Detection of N-H···O=C Hydrogen Bonds in 13C,15N-Labeled Nucleic Acids
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- 作者：Aizhuo Liu ; Ananya Majumdar ; Weidong Hu ; Abdelali Kettani ; Eugene Skripkin ; and Dinshaw J. Patel
- 刊名：Journal of the American Chemical Society
- 出版年：2000
- 出版时间：April 5, 2000
- 年：2000
- 卷：122
- 期：13
- 页码：3206 - 3210
- 全文大小：109K
- 年卷期：v.122,no.13(April 5, 2000)
- ISSN：1520-5126
文摘
We describe the first direct observation of N-H···O=C hydrogen bonding in nucleic acids via thefour-bond 4hJNiNj coupling within an N1i-H1i···O6j=C6j-N1j segment of a G·G·G·G tetrad. The experiment,two-dimensional (2D) HN(N)-TOCSY, makes use of band-selective 15N isotropic mixing to transfermagnetization exclusively via the 4hJNN couplings to yield correlations between N1Hi(
2) and N1j(1) acrossthe hydrogen-bonded segment. In a complementary experiment, 2D cross-polarization (CP)-H(N)CO-(NN)-TOCSY, employing band-selective heteronuclear 15N-13C cross-polarization sequences on either side of the15N-15N TOCSY period, correlations are obtained between N1Hi(2) and C6j(1) nuclei across the hydrogenbond. The symmetric A2X2-type coupling topology of the four-spin nitrogen system in the G·G·G·G tetradpermits accurate measurement of these couplings by a new procedure that fits the experimental data withknown analytical isotropic mixing transfer functions. The techniques are demonstrated on a G·G·G·G tetradformed within a novel dimeric quadruplex fold of a uniformly 13C/15N-labeled d(G-G-G-T-T-C-A-G-G) DNAsequence. The value of the 4hJNN coupling constant for this system is estimated to be 0.136 ± 0.021 Hz.
2) and N1j(1) acrossthe hydrogen-bonded segment. In a complementary experiment, 2D cross-polarization (CP)-H(N)CO-(NN)-TOCSY, employing band-selective heteronuclear 15N-13C cross-polarization sequences on either side of the15N-15N TOCSY period, correlations are obtained between N1Hi(2) and C6j(1) nuclei across the hydrogenbond. The symmetric A2X2-type coupling topology of the four-spin nitrogen system in the G·G·G·G tetradpermits accurate measurement of these couplings by a new procedure that fits the experimental data withknown analytical isotropic mixing transfer functions. The techniques are demonstrated on a G·G·G·G tetradformed within a novel dimeric quadruplex fold of a uniformly 13C/15N-labeled d(G-G-G-T-T-C-A-G-G) DNAsequence. The value of the 4hJNN coupling constant for this system is estimated to be 0.136 ± 0.021 Hz.