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13 C chemical shift tensors and secondary structure of poly‐ L ‐alanine by solid‐state two‐dimensional spin‐echo NMR and ab initio chemical shielding calculation
Author(s) -
Asakawa Naoki,
Takenoiri Masatoshi,
Sato Daisuke,
Sakurai Minoru,
Inoue Yoshio
Publication year - 1999
Publication title -
magnetic resonance in chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.483
H-Index - 72
eISSN - 1097-458X
pISSN - 0749-1581
DOI - 10.1002/(sici)1097-458x(199904)37:4<303::aid-mrc440>3.0.co;2-w
Subject(s) - chemistry , chemical shift , anisotropy , solid state nuclear magnetic resonance , ab initio , nuclear magnetic resonance spectroscopy , isotropy , electromagnetic shielding , ab initio quantum chemistry methods , alanine , crystallography , computational chemistry , nuclear magnetic resonance , molecule , stereochemistry , organic chemistry , materials science , physics , amino acid , biochemistry , quantum mechanics , composite material
Analyses of 13 C chemical shielding tensors for powdersamples of α‐helix‐rich poly‐ L ‐alanine (pALA) and the mechanically stretchedβ‐sheet pALA films were performed by solid‐statetwo‐dimensional spin‐echo (2DSE) NMRspectroscopy. From the iterative fitting of 2DSE spectra withspectrum simulations, information was obtained about the principalvalues of the chemical shift tensors (CST) for nuclei withsmall chemical shift anisotropy such as CH and CH 3 carbons. The experimental results show that the lowest shieldingcomponent, δ 11 , of L ‐alanine residueα‐ and β‐carbons are sensitive to theconformational changes and responsible for the behavior of theconformation‐dependent isotropic chemical shifts. Ab initio gauge‐invariant atomic orbital chemical shieldingcalculations were carried out in order to understand the correlationbetween the CST and the polypeptide conformation. ©1999