[Progress in application of THz-TDS to protein study].

Terahertz time-domain spectroscopy (THz-TDS) is a newly developed terahertz far infrared spectroscopy based on ultra-fast laser technology. Various applications of THz electromagnetic waves have been investigated by researchers in various fields, including life sciences, pharmaceutical, security detection and etc. THz-TDS has been proven a promising technique in biological and medical applications. Absorption spectrum in the THz range provides rich information about structure and weak interactions of molecules. It is expected that the THz waves can be applied to probing the interactions between antibody and antigen, drug and organism. Combining the characteristic of THz-TDS and its physical foundation in biomolecular spectroscopy, the paper provides a general review of the achievements of and the latest progresses in THz-TDS technology in the study of molecular structure, dynamics and label-free detection of amino acid, polypeptide and protein. Investigating the structure and dynamics of amino acids and polypeptides in low-frequency range is necessary and fundamental for comprehensive understanding of protein function. The absorption coefficients and refractive indices of different amino acids and peptides were summarized, and the results from different research groups were collected. The combination of absorption coefficient and refractive index enables us to discuss rigorously the dynamics of the total dipole moment of protein system. Biological polymers are expected to exhibit broad vibrational spectral features in the THz range corresponding to functionally relevant, global and subglobal collective modes with periods on the picosecond timescale. Some studies focused on the absorption spectrum of hydrated, dehydrated protein powder and solvated protein in an effort to monitor these collective motions. The results indicated that THz-TDS allows rapid characterization of the dynamical transition without label. However, THz technique is still in its infancy compared with other electromagnetic waves. The problem and the prospect of the application of THz-TDS at this stage are also discussed.