Modeling of the influence of conformation,isotopic substitution,and aqueous environment on the vibrational spectrum of L-glutamic acid

Quantum-mechanical calculations of optimized structures, harmonic force fields, and vibrational spectra were performed for 10 L-glutamic acid conformers. The vibrational spectra were interpreted using B3LYP/6-31+G** calculations for the stablest conformer. Satisfactory agreement between the experimental and theoretical data was obtained. Vibrational frequency shifts caused by isotopic substitution of various types in the L-glutamic acid molecule were analyzed taking into account the conformational structure and the influence of water medium and molecule ionization. Isotopic tags are suggested that can be used in biochemical studies taking into account their special characteristics.