The amide nitrogen-15 chemical shift tensors of four peptides determined from carbon-13 dipole-coupled chemical shift powder patterns

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).…”

“…It is worth pointing out that in our data this difference arises primarily from σ 22 , which is systematically higher in α-helix (by 7.8 ppm on average), while the other two components of the 15 N shielding tensor (particularly σ 11 ) show a considerably smaller and less systematic difference between the β-sheet and α-helix conformations (see Tables 3, 4). The calculated 15 N CSA values also agree with the solid state NMR measurements in short peptides Oas et al 1987;Hiyama et al 1988;Shoji et al 1989;Mai et al 1993;Wu et al 1995). 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.…”

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 J LS (ω) values included the effect of the overall rotational anisotropy 46,47 , calculated from the diffusion tensor characteristics (Table 1) and the orientation of a given NH vector reconstructed according to the crystal structure of GB3 (1IGD.pdb). For each residue, the experimental values of the spectral density function J(ω) at ω=0, ω N , and 0.87ω H were directly derived from the relaxation data (R 1 , R 2 , NOE) at each field strength using the reduced spectral density approximation 48,49 , as follows: (15) (16) (17) Altogether this resulted in 15 values of J(ω) per residue, five of which were J(0) values derived from different-field measurements and which are expected to be the same within experimental precision. The LS parameters, (S 2 , τ loc ), and the 15 N CSA value for each residue were obtained from an unconstrained nonlinear minimization of the following target function: (18) where the sum is over all available ω i values for a given residue, and δJ i represents the experimental error in J(ω i ).…”

“…Amide 15 N CSTs in proteins present a particular challenge, because they are susceptible to a variety of factors, including conformations (torsion angles) of both current and preceding residues, hydrogen bonding, solvent accessibility, long range electrostatics, etc 11-14 . The complete chemical shielding tensor could, in principle, be measured directly by solid-state NMR methods, and such studies provided valuable information on 15 N CSTs in short peptides [15][16][17][18][19][20][21] . However, applications of these techniques to uniformly labeled proteins are still in development.…”

Phosphorus-31 solid-state nuclear magnetic resonance study of monophosphazenes

“…Recent advances in the study of polycrystalline solids by nmr have led to an increase in the use of this technique to elucidate the structural and electronic characteristics of biological (1)(2)(3)(4)(5), organic (6-lo), inorganic ( 1 l,l2), and polymeric compounds (13,14). In principle, the nmr spectrum of a solid contains much more information on the chemical nature of a compound than the corresponding solution spectrum.…”