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Normal vibrations of crystalline polyglycine I
Author(s) -
Abe Yasuaki,
Krimm S.
Publication year - 1972
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.1972.360110905
Subject(s) - chemistry , antiparallel (mathematics) , dipole , force field (fiction) , amide , vibration , computational chemistry , coupling constant , molecular physics , crystallography , physics , organic chemistry , quantum mechanics , magnetic field
Abstract A valence force field has been refined for crystalline polyglycine I using its known antiparallel chain pleated‐sheet structure and without replacing the CH 2 group by a point mass. Polyglycine I and four of its isotopic derivatives were used in the refinement. The calculated frequencies are in good agreement with the observed, except for the amide I modes. It is shown that this is a consequence of the fact that no reasonable force field predicts a large D 10 term of the Miyazawa perturbation treatment. The amide I splittings can, however, be satisfactorily accounted for by introducing a direct interaction force constant between adjacent CO groups in neighboring chains. This can reasonably arise from transition dipole coupling and corresponds to the heretofore neglected D 11 term.