The effect of the flexibility of hydrogen bonding network on low-frequency motions of amino acids. Evidence from Terahertz spectroscopy and DFT calculations

Spectrochim Acta A Mol Biomol Spectrosc. 2018 Feb 15:191:8-15. doi: 10.1016/j.saa.2017.09.035. Epub 2017 Sep 20.

Abstract

Low-frequency modes of L-Asp and L-Asn were studied in the range from 0.1 to 3.0THz using time-domain Terahertz spectroscopy and density functional theory calculation. The results show that PBE-D2 shows more success than BLYP-D2 in prediction of THz absorption spectra. To compare their low-frequency modes, we adopted "vibrational character ID strips" proposed by Schmuttenmaer and coworkers [Journal of Physical Chemistry B, 117, 10444(2013)]. We found that the most intense THz absorption peaks of two compounds both involve severe distortion of their hydrogen bonding networks. Due to less rigid hydrogen bonding network in L-Asp, the side chain (carboxyl group) of L-Asp exhibits larger motions than that (carboxamide group) of L-Asn in low-frequency modes.

Keywords: Amino acids; DFT calculation; Hydrogen bonds; L-Asn; L-Asp; Terahertz spectroscopy.

MeSH terms

  • Amino Acids / chemistry*
  • Crystallization
  • Hydrogen Bonding
  • Models, Molecular*
  • Molecular Conformation
  • Motion*
  • Quantum Theory*
  • Terahertz Spectroscopy*
  • Vibration

Substances

  • Amino Acids