Raman Spectral Optical Activity of Aqueous Solutions of Some Amino Acids

Abstract

The Raman optical activity (ROA) spectra were measured for aqueous solutions of Lproline, L-hydroxyproline and L-lysine. The ROA signals for the CH₂ scissoring mode are very strong in the case of L-proline and L-lysine, while in the case of L-hydroxyproline, the ROA signal for this band is not observed. This result suggests that the ROA is related to the presence of chained CH₂ groups in the molecule, and that a strong vibrational coupling due to such a CH₂ chain structure contributes to the intensities of the ROA signal for this vibrational mode. The ROA pattern at wavenumbers higher than 1300 cm_-1 is generally common among the three amino acids employed, reflecting the common L-type steric configuration around the a-asymmetric carbon.