The effect of water on NMR spin-spin couplings in DNA: Improvement of calculated values by application of two solvent models
| Authors | |
|---|---|
| Year of publication | 2003 |
| Type | Article in Periodical |
| Magazine / Source | Physical Chemistry Chemical Physics |
| MU Faculty or unit | |
| Citation | |
| Field | Physical chemistry and theoretical chemistry |
| Keywords | NMR; coupling constants; DNA hairpin DFT |
| Description | A water solvent effects on isotropic one-bond 1J(X,H), 1J(C,X) and two-bond 2J(X,H), (X=C,N) indirect NMR spin-spin coupling constants measured previously in 13C, 15N-labeled DNA hairpin molecule d(GCGAAGC) were investigated theoretically at ab initio level by application of explicit and PCM models of solvent. Sensitivity of the Fermi contact contribution to the total J coupling towards the solvent inclusion calculated using coupled perturbed density functional theory with B3LYP hybrid functional is dominating, while the solvent shifts of the other three J contributions are negligible. Consideration of the solvent leads to the noticeable shift of especially 1J(C,H) couplings. The largest shift of 6.1 Hz was found for 1J(C8,H8) coupling in guanine. Further inclusion of solvent decreases mean absolute deviation between calculated and experimental J constants from 1.7 to 1.1 Hz for guanine, from 2.4 to 0.6 Hz for cytosine, and from 2.3 to 1.6 Hz for adenine. In the case of explicit solvent, the 1J(C8,H8) solvent shift seems to be sensitive to the magnitude of charge transfer from water sigma bonding O-H and Oxygen lone pair orbitals to the sigma* antibonding C8-H8, C8-N7, and C8-N9 orbitals of guanine. Both explicit and PCM solvent models provide similar improvement of calculated couplings. |
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