Raman spectroscopy of monohydrated L-asparagine up to 30 GPa

Amino acid crystals are important systems for investigating chemical bonds of biochemical interest. Raman spectroscopy was used to study the vibrational properties of monohydrated L-asparagine crystal submitted to high pressure. Under these conditions amino acids can undergo phase transition and, eventually, as is the case of L-alanine, transform to an amorphous phase. In this work monohydrated L-asparagine was submitted to pressures up to 30 GPa, twice the pressure for which L-alanine was observed to present the solid-amorphous phase transition. Up to the maximum pressure reached in the experiments, no evidence of amorphization was found in the present work. However, several modifications in the entire spectral range of the Raman spectrum (30-3600 cm super(-1)) suggest monohydrated L-asparagine undergoes a solid-solid phase transition at 10 GPa. The reversibility of the phase transition as well as the behavior of bands associated with hydrogen bond is also given.