Vibrational and structural properties of L-Alanyl-L-Phenylalanine dipeptide by Raman spectroscopy, infrared and DFT calculations

Abstract A study of vibrational and structural properties of l -Alanyl- l -Phenylalanine hydrophobic dipeptide (molecular formula C 12 H 16 N 2 O 3 ) is reported. The l -alanyl- l -phenylalanine is formed by two hydrophobic amino acids, L-alanine and l -phenylalanine, through a peptide bond. Individually these compounds have many important properties, including increasing immunity and providing energy to muscle tissue, brain and central nervous system ( l -alanine). We have performed measurements of Raman and Fourier transform infrared spectroscopy, between 3500-50 cm −1 and 4000-130 cm −1 , respectively, at ambient conditions. To support the experimental results calculations using the density functional theory (DFT) with B3LYP functional, 6–31 G ++ (d, p) basis sets and the polarizable continuum model of solvatation in an isolated molecule in the zwitterionic form were done. The assignment of the normal modes was described by the potential energy distribution analysis. In this way, it was possible to analyze the vibrational and structural properties of L-alanyl-L-phenylalanine, allowing the assignment of each vibrational normal mode of the molecular structure, associating them with those results obtained experimentally.