Normal mode analysis of glycine dipeptide in crystal conformation using a scaled ab initio force field
1992; Elsevier BV; Volume: 274; Linguagem: Inglês
10.1016/0022-2860(92)80164-d
ISSN1872-8014
Autores Tópico(s)Nonlinear Optical Materials Research
ResumoThe ab initio force field of glycine dipeptide, CH3CONHCH2CONHCH3, was computed at the 4-21 level for a conformation close to that in the crystal and with four intermolecular hydrogen bonds provided by four water molecules. The force constants of the peptide were scaled to fit the IR data previously measured by Koyama and Shimanouchi, Biopolymers, 6 (1968) 1037, for the crystalline molecule and four of its deuterated derivatives. A total of 132 assigned frequencies were fitted to an average error of 9 cm−1. The IR intensities were also calculated. The refined scale factors can be applied to other hydrogen-bonded peptides, allowing reliable predictions of vibrational spectra with a relatively small basis set. The results also provide a more complete and more accurate description of the modes of this basic model compound, which can be used to test other force fields for normal mode and molecular mechanics calculations of peptides.
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