%0 Journal Article %T Vibrational Analysis and Hydrogen-Bonding Effects on the Vibrational Modes of Zwitterionic DL-Tryptophan: IR Spectroscopy and DFT Calculations %A BOUKAOUD, A. %A CHIBA, Y. %A DEHBAOUI, M. %A GUECHI, N. %J Sigma Journal of Engineering and Natural Sciences %D 2019 %V 37 %P 1181-1198 %R