High-temperature Raman spectra of dipeptide α-L-aspartyl-L-alanine crystal

Crystals of dipeptide α-L-aspartyl-L-alanine (α-Asp-Ala), C₇H₁₂N₂O₅, were studied under high-temperature conditions through vibrational spectroscopy (IR and Raman) and thermal analysis (Differential Scanning Calorimetry - DSC). From the analysis of the results, it is possible to conclude that: (i) the studied material undergoes a reversible order-disorder phase transition at 373 K on heating, where several changes were observed in the vibrational spectra, especially with vibrational modes of the units that participate directly of the hydrogen bonds; (ii) the phase transition undergone by the α-Asp-Ala crystal (about 373 K) involves changes in hydrogen bonds, possibly the rupture of at least one of them, and change in the conformation of the molecules in the unit cell.