Amino acid chemistry in solution:: Structural study and vibrational dynamics of glutamine in solution.: An ab initio reaction field model

The self-consistent reaction field (SCRF) theory was used to study structural and vibrational features of the amino acid L-glutamine in solution. Raman and infrared spectra of this molecule in solutions of H(2)O and D(2)O were recorded and measured. The bands were firstly assigned on the basis of the isotopic shifts. An ab initio quadratic force field at the 6-31+G* level was achieved. The calculation simulated a polar solvent by placing the molecule in an ellipsoidal cavity surrounded by a continuum dielectric. The theoretical results, in terms of structural parameters, vibrational frequencies and descriptions, and infrared intensities, were in satisfactory agreement with the experimental data.