Terahertz Spectroscopic Study Of Biomolecules In Aqueous Solution Confined In Microfluidic Channels

Proteins,belong to a category of organic macromolecules participating in the formation of cells,are principally responsible for significant life activities in the organism.The qualitative and quantitative analysis for different kinds of proteins under different physiological conditions is an important index of protein function analysis,clinical diagnosis,recovery check,quality testing of biological products and so on.At present most of biological detection methods take advantages of the specific expression information of homologous antibody of the protein to determinate the presence or absence of the specific protein together with its quantity,calling for several sophisticated and tedious processes which spend more resources.As a kind of physical detection methods,THz technology eliminates the need for complex labeling processes in traditional biochemical detection methods,so it is very suitable for the label-free protein detection.The terahertz wave covered the energy range of the weak force within/between biological macromolecules,vibration of skeleton and dipole rotation,through the characteristic THz fingerprint spectrum of biological macromoleculars at terahertz band the qualitative analysis of biological macromolecules is permissible.Moreover protein content and conformational changes affect optical parameters at THz band.So the optical parameters are the main basis for detecting protein type,content and protein denaturation.This thesis first summarizes the characteristics of the terahertz wave and terahertz time-domain spectroscopy together with the research progress of terahertz spectroscopic technology detecting biological macromolecules.Then the thesis introduces several kinds of the currently used classic methodology for optical parameter extraction using transmitted-through THz-TDS.Because of the use of the thin microfluidic channels the effects of Fabry–Pérot interference on the optical parameters become more significantly,based on the predecessors' algorithms a more simple and targeted parameter extraction algorithm is developed.Finally this thesis focuses on expounding terahertz spectral characteristic research of proteins aqueous solutionin different liquid physical environment confined in microfluidic channels to study the physiological state of proteins.The study mainly includes two aspects: the hydration research of bovine serum albumin with different concentrations and the conformational change research of pepsin in different acid-base environment.Experimental results show that the optical parameters,such as refractive index and absorption coefficient,and bovine serum albumin concentration do not conform to the Lambert beer's law,because the increase of concentration of BSA protein molecules content results in the overlap of the hydration layer around BSA protein molecules.Absorption coefficient of the pepsin solution at p H = 3 and p H = 5,p H = 7 and p H = 8.5,p H = 11 respectively in three kinds of state,since only under the p H = 2 ~ 4 physiological conditions pepsin could ensure normal space conformation,under p H = 5~7 physiological conditions a fraction of structures of pepsin has changed and when the p H >8.5 pepsin is irreversible inactivated.The research results above provide the reliable basis for qualitative and quantitative detection of protein molecules using THz spectroscopy.