Terahertz spectra of l-phenylalanine and its monohydrate

Tingting Pan; Shaoping Li; Tao Zou; Zheng Yu; Bo Zhang; Chenyang Wang; Jianbing Zhang; Mingxia He; Hongwei Zhao

doi:10.1016/j.saa.2017.01.050

Terahertz spectra of l-phenylalanine and its monohydrate

Spectrochim Acta A Mol Biomol Spectrosc. 2017 May 5:178:19-23. doi: 10.1016/j.saa.2017.01.050. Epub 2017 Jan 26.

Authors

Tingting Pan¹, Shaoping Li², Tao Zou¹, Zheng Yu³, Bo Zhang¹, Chenyang Wang³, Jianbing Zhang³, Mingxia He⁴, Hongwei Zhao⁵

Affiliations

¹ School of Chemical Engineering, East China University of Science and Technology, Shanghai 200237, China; Division of Interfacial Water and Key Laboratory of Interfacial Physics and Technology, Shanghai Institute of Applied Physics, Chinese Academy of Sciences, Shanghai 201800, China.
² School of Chemical Engineering, East China University of Science and Technology, Shanghai 200237, China. Electronic address: spli@ecust.edu.cn.
³ Division of Interfacial Water and Key Laboratory of Interfacial Physics and Technology, Shanghai Institute of Applied Physics, Chinese Academy of Sciences, Shanghai 201800, China.
⁴ State Key Laboratory of Precision Measuring Technology and Instruments, School of Precision Instrument and Opto-electronics Engineering, Tianjin University, Tianjin 300072, China.
⁵ Division of Interfacial Water and Key Laboratory of Interfacial Physics and Technology, Shanghai Institute of Applied Physics, Chinese Academy of Sciences, Shanghai 201800, China. Electronic address: zhaohongwei@sinap.ac.cn.

PMID: 28157589
DOI: 10.1016/j.saa.2017.01.050

Abstract

The low-frequency vibrational property of l-phenylalanine (l-Phe) and l-phenylalanine monohydrate (l-Phe·H₂O) has been investigated by terahertz time-domain spectroscopy (THz-TDS) at room and low temperature ranging from 0.5 to 4.5THz. Distinctive THz absorption spectra of the two compounds were observed. Density functional theory (DFT) calculations based on the crystal structures have been performed to simulate the vibrational modes of l-Phe and l-Phe·H₂O and the results agree well with the experimental observations. The study indicates that the characterized features of l-Phe mainly originate from the collective vibration of molecules. And the characterized features of l-Phe·H₂O mainly come from hydrogen bond interactions between l-Phe and water molecules. l-Phe and l-Phe·H₂O were also verified by differential scanning calorimetry and thermogravimetry (DSC-TG) and powder X-ray diffraction (PXRD) examinations.

Keywords: DFT; Low-frequency vibration; Monohydrate; Terahertz absorption spectrum; l-Phenylalanine.