Chinese Journal of Magnetic Resonance ›› 2016, Vol. 33 ›› Issue (3): 378-394.doi: 10.11938/cjmr20160303

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Influences of Intermolecular Interactions on the 17O Nuclear Magnetic Parameters in Nucleic Acid Bases: A Theoretical Investigation

SONG Ben-teng1,2, CHU Yue-ying2, WANG Ji-qing1, ZHENG An-min2, DENG Feng2   

  1. 1. Hunan Key Laboratory of Green-Packaging and Application of Biological Nanotechnology, Hunan University of Technology, Zhuzhou 412008, China;
    2. State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics (Wuhan Institute of Physics and Mathematics, Chinese Academy of Sciences), Wuhan 430071, China
  • Received:2015-09-22 Revised:2016-07-12 Online:2016-09-05 Published:2016-09-05

Abstract:

The influence of hydrogen bonding on the shielding tensors and quadrupole coupling constant (QCC) of oxygen atoms in [17O-2] thymine, [17O-4] thymine, [17O-2] uracil, [17O-4] uracil, [17O-2] cytosine, and [17O-6] guanine monohydrate has been studied by high quality quantum chemical calculations with different cluster models. The results showed that both hydrogen bonding and van der Waals (vdW) interactions are crucial for accurate prediction of isotropic 17O chemical shifts (dO). In addition, experimentally measured 17O chemical shifts in these bases decrease with the increase of intermolecular hydrogen bonding interactions, and such interactions need to be accounted for in the theoretical models in order to obtain satisfactory calculated results. Relative to that of dO, the calculation of 17O shielding tensors (d11, d22 and d33) are even more model-dependent. NMR parameters calculated by periodic structure models taking all hydrogen bonding interactions and non-bonding vdW interactions into account were found to be in good agreement with the experimental results. Further analysis revealed that intermolecular hydrogen bonding-induced decrease of dO is mainly due to the increase of 17O negative charge density coming from the carboxyl (C=O) carbon. Furthermore, it was found that hydrogen bonding and weak interaction have remarkable effects on calculated 17O quadrupole coupling constant (QCC) as well. In conclusion, it is essential to take intermolecular hydrogen bonding and weak interactions into accounts in theoretical calculations in order to predict NMR parameters of biological samples correctly.

Key words: NMR, shielding tensor, quantum chemical calculation, nucleic acid bases, quadrupole coupling constant

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