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Analysis of the 1 H‐NMR spectra of ferrichrome peptides. II. The amide resonances
Author(s) -
Demarco Antonio,
Llinás Miguel,
Wüthrich Kurt
Publication year - 1978
Publication title -
biopolymers
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.556
H-Index - 125
eISSN - 1097-0282
pISSN - 0006-3525
DOI - 10.1002/bip.1978.360170308
Subject(s) - chemistry , ferrichrome , amide , crystallography , spectral line , stereochemistry , nmr spectra database , proton nmr , organic chemistry , biochemistry , physics , escherichia coli , astronomy , bacterial outer membrane , gene
The high‐resolution 1 H‐nmr study of the ferrichrome cyclohexapeptides, in d 6 ‐DMSO solutions, has been extended to the amide NH spectral region. A total of ten diamagnetic analogues of ferrichrome that differ in the coordinated metal ion (Al 3+ , Ga 3+ or Co 3+ ), the primary structure, the nature of the bidentate hydroxamate moiety, or the isotope compositions ( 14 N, 15 N) have been investigated. The 3 J αNH values reflect regiorous conformational isomorphism throughout the complete suite of analogues, quite independent of the residue occupancy of each site. Totally resolved amide multiplets have been obtained in most cases and the four‐line (doublet of doublets) appearances of glycyl NH resonances has been observed for the first times; these data enabled stereospecific assignment and accurate analysis of the NH‐CαH proton spin systems. The high resolution was made possible by the use of a suitable spectral deconvolution shceme at 360 MHz. The fine structure, extraordinarily well displayed in the 15 N‐peptide spectra, provides a series of parameter values whose consistency has been checked by computer simulation. Since the crystallographic structure for two of the ferric peptides is known to 0.002‐Å resolution, a 3 J vs θ correspondence could be confidently established. A Karplus curve was derived from the combined x‐ray and nmr data:\documentclass{article}\pagestyle{empty}\begin{document}$$ ^3 J_{\alpha {\rm NH}} = 5.4\cos ^2 \theta - 1.3\cos \theta + 2.2{\rm Hz} $$\end{document} It is suggested that seriously nonplanar amides can exhibit 3 J αNH values higher than predicted by the ferrichrome curve.