%0 DATA
%A Peter, Damberg
%A Jüri, Jarvet
%A Astrid, Gräslund
%D 2005
%T Limited Variations in ^{15}N CSA Magnitudes and Orientations in
Ubiquitin Are Revealed by Joint Analysis of Longitudinal and
Transverse NMR Relaxation
%U https://acs.figshare.com/articles/Limited_Variations_in_sup_15_sup_N_CSA_Magnitudes_and_Orientations_in_Ubiquitin_Are_Revealed_by_Joint_Analysis_of_Longitudinal_and_Transverse_NMR_Relaxation/3301027
%R 10.1021/ja045956e.s001
%2 https://acs.figshare.com/ndownloader/files/5138761
%K amide nitrogen TROSY
%K order parameters
%K shielding
%K exchange terms
%K Transverse NMR Relaxation
%K K öv Batta
%K magnitude
%K 15 N CSA Magnitudes
%K variability
%K relaxation
%K 800 MHz data
%K NH bond
%K uncertainty
%K ppm
%K anisotropie
%K chemical shift tensors
%K orientation
%K variation
%X The site-specific magnitudes and orientations of the chemical shift tensors have been estimated
for 70 backbone ^{15}N-nuclei in human ubiquitin from the field dependence of dynamic independent ratios
between relaxation rates, both longitudinal and transverse, measured at 9.4, 11.7, 14.1, and 18.8 T. The
results were jointly analyzed with previously published relaxation data [Fushman; Tjandra; Cowburn. *J.
**Am. Chem. Soc.* **1998**, *120*, 10947−10952] [Kövér; Batta. *J. Mag. **Reson*. **2001**, *150*, 137−146]. The
effective magnitudes of the anisotropies distribute around 169 ppm with a variability of 5 ppm. The orientation
factors, reflecting the orientation of the CSA relative to the NH bond, distribute around −0.80 with a variability
of 0.04, which corresponds to an angle between the symmetry axis of an assumed axially symmetric shielding
tensor and the NH bond of 21.4°, and a variability of 2.3°. Correlations with the isotropic ^{15}N-chemical
shifts are observed. Variations in the shielding anisotropies add uncertainty to the obtained order parameters
proportional to the square of the magnetic field, when data are analyzed using an assumed invariant CSA
tensor for all sites. Around 3% additional uncertainty in the order parameters for 800 MHz data is expected.
The optimal TROSY field for amide nitrogen TROSY is estimated, with only marginal variations due to
site-to-site variations. Variations in the shielding tensors add uncertainty to the exchange terms calculated
from cross-correlation rates. An approach for estimating the exchange terms is suggested, where the
uncertainty due to CSA-variations is minimized.