Open AccessIntermolecular Interaction Effects in the Amide I Vibrations of β Polypeptides
Author(s) -
Samuel Krimm,
Yukichi Abe
Publication year - 1972
Publication title -
proceedings of the national academy of sciences of the united states of america
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 5.011
H-Index - 771
eISSN - 1091-6490
pISSN - 0027-8424
DOI - 10.1073/pnas.69.10.2788
Subject(s) - amide , intermolecular force , perturbation (astronomy) , chemistry , perturbation theory (quantum mechanics) , vibration , dipole , computational chemistry , normal mode , intermolecular interaction , crystallography , coupling constant , chemical physics , stereochemistry , molecular physics , physics , molecule , quantum mechanics , organic chemistry
Previous perturbation treatments of the Amide I vibrations of β polypeptides are inconsistent with a detailed normal coordinate analysis of crystalline polyglycine I. This analysis indicates that theD 10 interaction constant is essentially zero, rather than the large value (about 20 cm-1 ) required by the earlier application of the perturbation theory. It is suggested that the previously neglectedD 11 term should be included in the perturbation expression, and it is shown that the physical origin of such a term can be accounted for by transition dipole coupling. This mechanism is shown to give a reasonable explanation of splittings of the C=O stretching vibrations in hydrogenbonded carboxylic acid dimers. Its application to β polypeptides provides a satisfactory interpretation of splittings in the Amide I modes.