Correlations between Terahertz Spectra and Molecular Structures of 20 Standard <em>α</em>-Amino Acids

Abstract

All 20 standard polycrystalline α-amino acids were examined using terahertz time-domain spectroscopy (THz-TDS) at room temperature. They are strikingly sensitive to the THz pulse and yield a complete set of THz fingerprint spectra between 0.2 and 3.0 THz. These spectra were compared to those from previous reports in terms of spectral shape and frequencies of absorption peaks. We validated the characteristic absorption peaks and provided supplementary data. For the first time, correlations between THz spectral peaks and the molecular structures of amino acids are revealed and a classification of amino acids based on both molecular structures and THz spectra was established. These correlations can help identify amino acids, trace some functional groups, and examine if the THz spectra are dominated by internal or intermolecular vibrations. These correlations can thus promote the application of THz spectroscopy in the study of biological and medicinal materials in the biomedical fields.