| Terahertz Time-Domain Spectrum(THz-TDS) has the characteristics of a high signal to noise ratio and high sensitivity. It has been the hot spot of many scientists since the 1980s. The energy levels of the weak intermolecular interactions and the rotation and vibration of the molecule seat in the range of terahertz wave, which makes terahertz time-domain spectroscop-y technique is getting more and more attention. In order to study the terahertz spectroscopy of large molecular compounds, in this paper, the terahertz absorption spectra of the protein compounds were analyzed.Firstly, by using transmission type terahertz time-domain spectroscopy,20 kinds of natural a amino acids were detected, and their characteristic absorption spectrum in the range of 0～2.7THz were obtained. Based on a preliminary theoretical calculation,found that the differences of the amino acid molecular structure will lead to different absorption of terahertz,which including the differences of the group on the side chain, the length of the aliphatic substituent and and isomers, these factors caused the differences of the molecular rotation and twist. And THz absorption spectra database of amino acid was established. After the comparison of THz absorption spectra database of amino acid and other studies database, the accuracy of the experimental method in this article were verified.Then four kinds of peptides were detected by using terahertz time-domain spectroscopy, and their characteristic absorption spectrum within the effective range of THz are obtained, found that the basic composition of peptide molecules,different molecular space structure, the intramolecular and intermolecular hydrogen bonding, the rotation and twist of peptide bonds, these factors will lead to a different Terahertz Characteristics Absorption.Finally, five representative protein macromolecules were detected by using terahertz time-domain spectroscopy and terahertz time-domain spectroscopy air bias coherent detection of terahertz technology. By using the normal mode and molecular dynamic simulation, found that many normal modes of vibration superposition changed the Terahertz Characteristics Absorption, and the vibration mode will change along with the deformation of any level of structure in protein.By studying terahertz absorption spectrum of protein compounds, the database of terahertz spectrum are been enriched and expanded. It provides a new simple and convenient means to analysis and identification of proteins. And for the subsequent detection of other biochemical macromolecules such as toxins, explosives and dangerous biochemical goods provides a technical basis. |
