ISSN:
1573-5001
Keywords:
Protein
;
NMR
;
Chemical shift
Source:
Springer Online Journal Archives 1860-2000
Topics:
Biology
,
Chemistry and Pharmacology
Notes:
Summary The chemical shifts of CαH protons have been calculated for 9 proteins, based on coordinates taken from high-resolution crystal structures. Chemical shifts were calculated using ring-current shifts, shifts arising from magnetic anisotropies of bonds, and shifts arising from the polarizing effect of polar atoms on the Cα-H bond. The parameters used were refined iteratively to give the best fit to (experimental — random coil) shifts over the set of 9 proteins. A further small correction was made to the averaged Gly CαH shift. The calculated shifts match observed shifts with correlation coefficients varying between 0.45 and 0.86, with a standard deviation of about 0.3 ppm. The differences between calculated and observed shifts have been studied in detail, including an analysis of different crystal structures of the same protein, and indicate that most of the differences can be accounted for by small differences between the structure in solution and in the crystal. Calculations using NMR-derived structures give a poor fit. The calculations reproduce the experimentally observed differences between chemical shifts for CαH in α-helix and β-sheet. Most of the differentiation in secondary structure-dependent shifts arises from electric field effects, although magnetic anisotropy also makes a large contribution to the net shift. Applications of the calculations to assignment (including stereospecific assignment) and structure determination are discussed.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF02192802
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