Terahertz Spectroscopic Investigation Of Short-chain Peptides

Terahertz (THz) radiation, which occupies a large portion between the infrared and microwave bands, belongs to far-infrared band. In the last decade, rapid progress in ultra-fast laser technology provides a steady and reliable optical source for the THz pulses generation, which greatly promotes the research in the THz waveband that is difficult to access before. THz time-domain spectroscopy (THz-TDS) which developed in the 1980's, is an extremely promising coherent technique since it has the advantages of high signal to noise ratio, doesn't need low temperature instrument and so on. THz-TDS has been utilized in a wide range of research fields in the past ten years. The collective nature modes of most bio-molecules are located in THz range. In addition; THz radiation has low photon energies and will not cause harmful photo-ionization in biological tissues. Owing to these advantages, THz-TDS technology is a hot topic for nondestructive sensing in the bio-related fields.This paper investigated several kinds of short-chain peptides utilizing the facilities provided by THz spectrum and imaging laboratory of Capital Normal University. THz spectra of these peptides were studied both in experiment and theory. So the research activities of this thesis focused on the experimental measurement and theoretical analysis.In experiment, this paper's work includes:1. The flow for sample preparation and the influence of sample content for THz spectra were discussed in detail. It is helpful for bio-material's sample preparation.2. The THz spectra of short-chain peptides were measured by using THz-TDS, the pure sample and mixed sample made of peptides with polyethylene in different mass ratio were studied in THz region. The different mass rations result in different valid frequency range and absorption coefficients due to their different absorption properties. The THz spectra of refractive index and absorption coefficient of pure sample and mixed sample were presented.3. The IR spectra of short-chain peptides were measured by using FTIR. In the theoretical side, this paper focused on the following aspects:1. Theoretical calculation of short-chain peptides based on density functional theory (DFT) according to the literature. The IR and THz spectra were obtained by calculation.2. In order to get the more reasonable simulated results, the initial structure influence to...