Ab initio calculations of external charge effects on the isotropic 13C, 15N and 17O nuclear shieldings of amides

Hansen, Poul Erik; Abildgaard, Jens; Hansen, Aage E.

doi:10.1016/0009-2614(94)00545-1

Cited by 11 publications

(7 citation statements)

References 23 publications

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“…For a linear hydrogen bond with an NH···OH 2 distance of 1.8 Å and Φ/Ψ = 180°/180°, 1 Δ 15 N(D) decreases by 0.26 ppm, whereas decreases of ~0.52 ppm are found for other Φ/Ψ combinations. The difference is probably due to electric fields in the N i –H bond direction, which are largest for the 180°/180° conformation because the carbonyl oxygen of C′ i lies close to and at the smallest angle to the N–H bond (Hansen et al 1994 ) (dashed green line in Fig. 5 ).…”

Section: Resultsmentioning

confidence: 99%

Deuterium isotope effects on 15N backbone chemical shifts in proteins

et al. 2009

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Quantum mechanical calculations are presented that predict that one-bond deuterium isotope effects on the 15 N chemical shift of backbone amides of proteins, 1 D 15 N(D), are sensitive to backbone conformation and hydrogen bonding. A quantitative empirical model for 1 D 15 N(D) including the backbone dihedral angles, U and W, and the hydrogen bonding geometry is presented for glycine and amino acid residues with aliphatic side chains. The effect of hydrogen bonding is rationalized in part as an electric-field effect on the first derivative of the nuclear shielding with respect to N-H bond length. Another contributing factor is the effect of increased anharmonicity of the N-H stretching vibrational state upon hydrogen bonding, which results in an altered N-H/N-D equilibrium bond length ratio. The N-H stretching anharmonicity contribution falls off with the cosine of the N-HÁÁÁO bond angle. For residues with uncharged side chains a very good prediction of isotope effects can be made. Thus, for proteins with known secondary structures, 1 D 15 N(D) can provide insights into hydrogen bonding geometries.

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Section: Resultsmentioning

confidence: 99%

Deuterium isotope effects on 15N backbone chemical shifts in proteins

et al. 2009

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“…However, it is still important to evaluate the basis set dependence. Extensive theoretical work has been done in this area; however, most previous studies have mainly focused on the isotropic 17 O chemical shielding constants arising from a handful of isolated small molecules. − It remains an open question as to whether extensive hydrogen-bonded molecular clusters present some new challenges to the current quantum chemical methodologies. In several recent studies, we examined the 17 O CS tensors of various oxygen-containing functional groups in extensive H-bonding environment. − These studies suggested that B3LYP/D95** and B3LYP/6-311++G** calculations are adequate in reproducing experimental 17 O NMR results.…”

Section: Resultsmentioning

confidence: 99%

“…h i b i t e d .arising from a handful of isolated small molecules. [55][56][57][58][59][60][61][62][63][64] It remains an open question as to whether extensive hydrogen-bonded molecular clusters present some new challenges to the current quantum chemical methodologies. In several recent studies, we examined the 17 O CS tensors of various oxygen-containing functional groups in extensive H-bonding environment.…”

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A Combined Experimental and Theoretical ¹⁷O NMR Study of Crystalline Urea: An Example of Large Hydrogen-bonding Effects

Dong

Ida

2000

J. Phys. Chem. A

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We report the first experimental determination of the carbonyl 17O electric-field-gradient (EFG) tensor and chemical-shift (CS) tensor of a urea-type functional group, R1NHC(O)NHR2. Analysis of magic-angle spinning (MAS) and stationary 17O NMR spectra of crystalline [17O]urea yields not only the principal components of the carbonyl 17O EFG and CS tensors, but also their relative orientations. The carbonyl 17O quadrupole coupling constant (QCC) and the asymmetry parameter (η) in crystalline urea were found to be 7.24 ± 0.01 MHz and 0.92, respectively. The principal components of the 17O CS tensor were determined: δ11 = 300 ± 5, δ22 = 280 ± 5 and δ33 = 20 ± 5 ppm. The direction with the least shielding, δ11, is perpendicular to the CO bond and the principal component corresponding to the largest shielding, δ33, is perpendicular to the NC(O)N plane. The observed 17O CS tensor suggests that, in crystalline urea, the 17O paramagnetic shielding contributions from the σ → π* and π → σ* mixing are greater than that from the n → π* mixing. Quantum chemical calculations revealed very large intermolecular H-bonding effects on the 17O NMR tensors. It is demonstrated that inclusion of a complete intermolecular H-bonding network is necessary in order to obtain reliable 17O EFG and CS tensors. B3LYP/D95** and B3LYP/6-311++G** calculations with a molecular cluster containing 7 urea molecules yielded 17O NMR tensors in reasonably good agreement with the experimental data.

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“…This approach is different from others studies that employ atomic charges or charge dipoles in order to reproduce specific effect arising from charges or polar groups in proteins or to generate dipolar perturbations. [64][65][66][67][68][69][70]…”

Section: Background Charge Perturbationmentioning

confidence: 99%

Modelling the influence of hydrogen bond network on chemical shielding tensors description. GIAO-DFT study of WALP23 transmembrane α-helix as a test case

Rougier

Milon

Réat

et al. 2010

Phys. Chem. Chem. Phys.

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Density Functional Theory (B3LYP/6-31G(d,p)) calculations of (15)N amide and (13)C carbonyl NMR chemical shielding tensors have been performed on WALP23trans-membrane alpha-helix peptide and compared to solid state NMR experiment performed on [(13)C(1)-Ala(13), (15)N-Leu(14)] specifically labelled peptide powder sample. Using either theoretical results obtained on the whole peptide or experimental data as reference, several simplest chemical models have been explored in order to reduce the computational cost while maintaining good theoretical accuracy. From this study, it appears that the hydrogen bond (N-H...O=C) network that exists in the alpha-helix has a major influence on the chemical shielding tensor and more specifically on the carbonyl (13)C sigma(22) eigenvalue. We show that a small truncated WALP_7 model is not adequate for (13)C(1) NMR description. The application of an external electric field in order to model the hydrogen bond network allows calculating chemical shielding tensors with accurate eigenvalues while the associated eigenvectors are largely modified. Finally, a 23 residues polyglycine peptide that includes the Alanine and Leucine residues for which NMR parameters must be calculated is proposed as the chemical model. This model is sufficient to mostly reproduce the calculation performed on WALP23 with major gain in computational time. Moreover, the application of a low intensity external electric field allows reaching the experimental accuracy for the determination of the eigenvalues.

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Ab initio calculations of external charge effects on the isotropic 13C, 15N and 17O nuclear shieldings of amides

Cited by 11 publications

References 23 publications

Deuterium isotope effects on 15N backbone chemical shifts in proteins

Deuterium isotope effects on 15N backbone chemical shifts in proteins

A Combined Experimental and Theoretical ¹⁷O NMR Study of Crystalline Urea: An Example of Large Hydrogen-bonding Effects

Modelling the influence of hydrogen bond network on chemical shielding tensors description. GIAO-DFT study of WALP23 transmembrane α-helix as a test case

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Ab initio calculations of external charge effects on the isotropic 13C, 15N and 17O nuclear shieldings of amides

Cited by 11 publications

References 23 publications

Deuterium isotope effects on 15N backbone chemical shifts in proteins

Deuterium isotope effects on 15N backbone chemical shifts in proteins

A Combined Experimental and Theoretical 17O NMR Study of Crystalline Urea: An Example of Large Hydrogen-bonding Effects

Modelling the influence of hydrogen bond network on chemical shielding tensors description. GIAO-DFT study of WALP23 transmembrane α-helix as a test case

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A Combined Experimental and Theoretical ¹⁷O NMR Study of Crystalline Urea: An Example of Large Hydrogen-bonding Effects