Premium
Theoretical 13 C chemical shift, 14 N, and 2 H quadrupole coupling‐ constant studies of hydrogen bonding in L ‐alanylglycine dipeptide
Author(s) -
Tafazzoli M.,
Amini S. K.
Publication year - 2008
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/mrc.2185
Subject(s) - chemistry , dipeptide , molecule , quadrupole , coupling constant , hydrogen bond , electric field gradient , crystallography , hydrogen , crystal structure , computational chemistry , atomic physics , physics , organic chemistry , peptide , biochemistry , particle physics
13 C chemical shieldings and 14 N and 2 H electric field gradient (EFG) tensors of L ‐alanylglycine ( L ‐alagly) dipeptide were calculated at RHF/6–31 + + G** and B3LYP/6–31 + + G** levels of theory respectively. For these calculations a crystal structure of this dipeptide obtained from X‐ray crystallography was used. Atomic coordinates of different clusters containing several L ‐alagly molecules were used as input files for calculations. These clusters consist of central and surrounding L ‐alagly molecules, the latter forming short, strong, hydrogen bonds with the central molecule. Since the calculations did not converge for these clusters, the surrounding L ‐alagly molecules were replaced by glycine molecules. In order to improve the accuracy of calculated chemical shifts and nuclear quadrupole coupling constants (NQCCs), different geometry‐optimization strategies were applied for hydrogen nuclei. Agreement between calculated and experimental data confirms that our optimized coordinates for hydrogen nuclei are more accurate than those obtained by X‐ray diffraction. Copyright © 2008 John Wiley & Sons, Ltd.