Glycyl CαChemical Shielding in Tripeptides: Measurement by Solid-State NMR and Correlation with X-ray Structure and Theory
- 13 September 2002
- journal article
- research article
- Published by American Chemical Society (ACS) in Journal of the American Chemical Society
- Vol. 124 (40) , 11894-11899
- https://doi.org/10.1021/ja026700g
Abstract
We report here 13Cα chemical shielding parameters for central Gly residues in tripeptides adopting α-helix, β-strand, polyglycine II, and fully extended 2° structures. To assess experimental uncertainties in the shielding parameters and the effects of 14N−13Cα or 15N−13Cα dipolar coupling, stationary and magic angle spinning (MAS) spectra with and without 15N decoupling were obtained from natural abundance and double-labeled samples containing [2-13C, 15N]Gly. We find that accurate (15N decoupled 1D or 2D MAS spectra of double-labeled samples. Compared to variations of isotropic shifts with peptide angles, those of 13Cα shielding anisotropy and asymmetry are greater. Trends relating shielding parameters to the 2° structure are apparent, and the correlation of the experimental values with unscaled ab initio shielding calculations has an rms error of 3 ppm. Using the experimental data and the ab initio shielding values, the empirical trends relating the 2° structure to shielding are extended to the larger range of torsion angles found in proteins.Keywords
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