A DFT Study of the Interresidue Dependencies of Scalar J-Coupling and Magnetic Shielding in the Hydrogen-Bonding Regions of a DNA Triplex
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- 作者：Michael Barfield ; Andrew J. Dingley ; Juli Feigon ; and Stephan Grzesiek
- 刊名：Journal of the American Chemical Society
- 出版年：2001
- 出版时间：May 2, 2001
- 年：2001
- 卷：123
- 期：17
- 页码：4014 - 4022
- 全文大小：128K
- 年卷期：v.123,no.17(May 2, 2001)
- ISSN：1520-5126
文摘
Scalar coupling constants and magnetic shieldings in the imino hydrogen-bonding region ofHoogsteen-Watson-Crick T·A-T and C+·G-C triplets have been calculated as a function of the distancebetween proton donor and acceptor nitrogen atoms. The Fermi contact contributions to h2J(15N-H···15N),1J(15N-1H), and h1J(1H···15N) were computed using density functional theory/finite perturbation theory (DFT/FPT) methods for the full base triplets at the unrestricted B3PW91/6-311G** level. Chemical shifts 
(1H) and(15N) were obtained at the same level using the gauge including atomic orbital (GIAO) method for magneticshielding. All three scalar couplings and all three chemical shifts are strongly interrelated and exhibit monotonicchanges with base pair separation. These correlations are in conformity with experimental data for a 32-nucleotide DNA triplex. The results suggest that both chemical shifts and coupling constants can be used togain information on H-bond donor-acceptor distances in nucleic acids. In addition to the DFT/FPT calculations,a simple three-orbital model of the N-H···H bond and a sum-over-states analysis is presented. This modelreproduces the basic features of the H-bond coupling effect. In accordance with this model and the DFTcalculations, a positive sign for the h2JNN coupling is determined from an E.COSY experiment.
(1H) and(15N) were obtained at the same level using the gauge including atomic orbital (GIAO) method for magneticshielding. All three scalar couplings and all three chemical shifts are strongly interrelated and exhibit monotonicchanges with base pair separation. These correlations are in conformity with experimental data for a 32-nucleotide DNA triplex. The results suggest that both chemical shifts and coupling constants can be used togain information on H-bond donor-acceptor distances in nucleic acids. In addition to the DFT/FPT calculations,a simple three-orbital model of the N-H···H bond and a sum-over-states analysis is presented. This modelreproduces the basic features of the H-bond coupling effect. In accordance with this model and the DFTcalculations, a positive sign for the h2JNN coupling is determined from an E.COSY experiment.