Pressure-dependent studies of amino acids crystals have been performed for more than two decades. The interest comes not only due the biological appealing of these materials but also because in the solid state, hydrogen bonds are the main responsible for their structural stability, being also related to their physical and chemical properties.

In this work we investigated the vibrational properties of DL-isoleucine crystals by using Raman spectroscopy. DL-isoleucine single crystals were grown by the slow evaporation method at ambient temperature. At ambient conditions the mode assignment was done in terms of the Potential Energy Distribution (PED) through density functional theory calculations. Their vibrational properties were studied at ambient temperature as a function of pressure by Raman scattering.. The pressure-dependent investigation shows modifications in the Raman spectra recorded between 30 and 3200 cm^-1  that were interpreted as phase transitions undergone by the crystal between 1.3 and 1.9 GPa and between 3.6 and 5.1 GPa. Finally, stress was simulated on the unit cell of the crystal from ambient up to 5.0GPa.