Well-resolved absorption spectra of benzoic acid and its derivatives with one hydrogen atom replaced by a substituent group CH3, OH, NH2 or NO2 were reported in the frequency region between 6 and 67 cm^-1 at room temperature with terahertz time-domain spectroscopy （THz-TDS）. These substances can be distinguished easily based on the terahertz absorption spectra. The measurements suggested that even minor changes in the molecular configuration and chemical composition lead to distinct differences in THz spectrum. Density functional theory （DFT） method was used to assist the analysis and assignment of the individual THz absorption spectra of benzoic acid and its methyl derivatives. Observed THz responses of samples can be assigned to the collective vibrations associated with intermolecular hydrogen bonds.
The photooxidation damage of lysozyme under 315-375 nm irradiation in the presence of riboflavin was studied by using sodium dodecyl sulfate-polyacrylamide gel electrophoresis(SDS-PAGE).Indica- tions showed that the mechanisms and products of oxidative damage were relative to the concentra- tion of riboflavin,the time of irradiation and the ambience.The type I process was examined in a nitrogen saturated solution,whereas both type I and type II were observed in an aerobic atmosphere and type II was the dominant process.The study also suggested that antioxidants,such as melatonin, can reduce the damage of lysozyme effectively.
The well-resolved absorption spectra of D-xylose,D-ribose,D-arabinose,D-lyxose and other related substances in the spectral region between 0.3 and 2.0 THz are measured using tera-hertz time-domain spectroscopy(THz-TDS)at 295 K.Comparing the absorption spectra of different chemicals,we can distinguish the samples easily.Thus THz-TDS is demonstrated to be a power and characteristic spectral tool,which is highly sensitive to the minor changes of the molecular structures and can be applied to detect and analyze similar materials.
GE MinZHAO HongweiJI TeYU XiaohanWANG WenfengLI Wenxin
