Raman Spectra and Normal Coordinate Analysis of the N1−H and N3−H Tautomers of 4-Methylimidazole: Vibrational Modes of Histidine Tautomer Markers

Autor:	Hideo Takeuchi, Shinji Hashimoto, Kunio Ono, Akira Toyama
Rok vydání:	2001
Předmět:	Chemistry Tautomer chemistry.chemical_compound symbols.namesake Crystallography Ab initio quantum chemistry methods Computational chemistry Molecular vibration symbols 4-Methylimidazole Imidazole Density functional theory Physical and Theoretical Chemistry Raman spectroscopy Histidine
Zdroj:	The Journal of Physical Chemistry A. 106:3403-3412
ISSN:	1520-5215 1089-5639
DOI:	10.1021/jp0124185
Popis:	The imidazole ring of histidine exists in two tautomeric forms in neutral-to-basic aqueous solution, and the tautomerism of the histidine residue sometimes plays a key role in catalytic reactions of enzymes. We have investigated the molecular vibrations of two tautomers of 4-methylimidazole (4-MeIm), a model compound for the histidine side chain, by Raman spectroscopy and ab initio calculations based on the density functional theory (DFT) approach. Examination of the temperature dependence of Raman intensity revealed nine pairs of bands characteristic of the N1-protonated and the N3-protonated tautomers of 4-MeIm at 1576/1596, 1452/1427, 1304/1344, 1265/1259, 1229/1234, 1165/1149, 1088/1104, 996/1014, and 942/934 cm-1. Five to six pairs of tautomerism-sensitive Raman bands were also identified for each of the C2-, N-, and C2,N-deuterated analogues of 4-MeIm. The observed Raman wavenumbers were used to determine nine scaling factors for the in-plane force constants derived from DFT calculations using the 6...
Databáze:	OpenAIRE
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