Friday, March 3, 2017

Abstract-Research on the Terahertz Absorption Spectra of Histidine Enantiomer (L) and its Racemic Compound (DL)

Tao Zhou, Yidong Wu, Juncheng Cao, Liangliang Zou, Jie Yuan, Zhenwei Yao, and Gongjie Xu

Terahertz time-domain spectroscopy (THz-TDS) is used to investigate the absorption spectra of polycrystalline L- and DL-histidine in the frequency range of 10–100 cm-1. The spectra exhibit distinct differences in peak frequencies between the enantiomer (L-histidine) and racemic compound (DL-histidine). The observed spectral differences are attributed to the intermolecular interactions. With the density function theory (DFT) method, the frequencies of vibrational modes of L-histidine and DL-histidine in the THz range are calculated and well assigned according to the measured spectra. The origin of the observed vibrational modes is found to be non-localized and of a collective (phonon-like) nature, which points to the lattice and skeleton vibrations mediated by the hydrogen bond. Furthermore, we propose and demonstrate a method for determining the composition ratio of histidine mixtures based on the THz absorption spectra.
© 2016 The Author(s)
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