Chemical Shift Anisotropy Tensors of Carbonyl, Nitrogen, and Amide Proton Nuclei in Proteins through Cross-Correlated Relaxation in NMR Spectroscopy

Abstract

The principal components and orientations of the chemical shift anisotropy (CSA) tensors of the carbonyl (C'), nitrogen (N), and amide proton (H(N)) nuclei of 64 distinct amide bonds in human ubiquitin have been determined in isotropic solution by a set of 14 complementary auto- and cross-correlated relaxation rates involving the CSA interactions of the nuclei of interest and several dipole-dipole (DD) interactions. The CSA parameters thus obtained depend to some degree on the models used for local motions. Three cases have been considered: restricted isotropic diffusion, three-dimensional Gaussian axial fluctuations (3D-GAF), and independent out-of-plane motions of the NH(N) vectors with respect to the peptide planes.

Variability of the 15N Chemical Shielding Tensors in the B3 Domain of Protein G from 15N Relaxation Measurements at Several Fields. Implications for Backbone Order Parameters

“…The CSA distribution in ubiquitin, reconstructed from the individual CST components reported in ref 30 , is in a better agreement with our data for GB3: the standard deviations in these CSAs range from 10.1 to 13.7 ppm, and the site-tosite variability, Λ, from 7.8 to 10.5 ppm, depending on the model of local motion.…”

Density functional calculations of 15N chemical shifts in solvated dipeptides

“…A good agreement with the experimental data is also found for the angle β between the least shielded component (σ 11 ) of the 15 N shielding tensor and the NH bond. The values of β obtained here, from 13.5° to 19.8°, are well in the range of the experimental values (12°-24°) obtained by different NMR techniques, both solution and solid-state Oas et al 1987;Hiyama et al 1988;Shoji et al 1989;Mai et al 1993;Fushman et al 1998;Cornilescu and Bax 2000;Kurita et al 2003;Loth et al 2005;Hall and Fushman 2006;Vasos et al 2006). There seems to be a weak correlation between the β angle and secondary structure, with slightly smaller angles for the β-sheet than for the α-helix (mean β angles are 14.8° and 16.5°, respectively).…”

“…These differences in the asymmetry of 15 N shielding between the two backbone conformations could be related to the differences in the orientation of the tensor. The absolute values of the asymmetry are somewhat higher than the experimentally observed in solution (Cornilescu and Bax 2000;Loth et al 2005) but comparable to solid-state NMR data (Wylie et al 2006), which likely reflects motional averaging expected to be more pronounced in proteins in solution.…”

Determination of the antisymmetric part of the chemical shift anisotropy tensor via spin relaxation in nuclear magnetic resonance

“…If amide backbone nitrogen nuclei in slowly tumbling proteins have similar anti-CSA components ͑which remains to be shown͒, it would be important to take these components into consideration whenever the precision of the measurements is better than 1% at 950 MHz. This level of precision can indeed be achieved 24,41,42 but hardly in routine experiments.…”

“…Due to the increasing popularity of very high static magnetic fields in NMR studies of biomolecules, the effects of anti-CSA tensor components become a topical issue, since the contribution of the CSA ͑including its anti-CSA component͒ to relaxation is proportional to the square of the static field. When CSA tensors can be obtained both from solid-state 22,23 and solution 24 NMR, it is important to have an estimate of the contributions of the anti-CSA components to relaxation rates in liquids since they can be a source of discrepancies.…”