Studies On The Interaction Of Three Biological Macromolecules With Chlorogenic Acid

Protein plays an important part in life process. With the further investigating of the protein research, the interaction of protein and ligands has become a hot spot on life science. It can be helpful to understand the binding nature of the small ligands to protein molecules and structural features of protein, develop new methods for analyzing protein. In this paper, the interactions of CA with three proteins were investigated by UV-Vis absorption spectroscopy, fluorescence spectroscopy, circular dichroism (CD) spectroscopy and fourier transform infrared spectroscopy. Lysozme and serum albumin were employed as the model proteins to study their interaction mechanism. The dissertation included four chapters.In the first part, overviews. It was summarized the properties of CA, the structures and functions of LYS and Serum proteins. The methods and significances of the research on the interaction between small molecules and proteins were also introduced briefly.In the second part, study on the interaction between LYS and CA. It was investigated by UV-Vis absorption spectroscopy, fluorescence spectroscopy, circular dichroism (CD) spectroscopy and fourier transform infrared spectroscopy. In different pH conditions, the absorption spectrum of CA also changed in the peak shape and shift. The fluorescence analysis showed that it was a static quenching mechanism between the interaction of LYS and CA when CA in the low concentration, while CA in the high concentration of4.0×10-5mol/L, quenching mechanism was a dynamic quenching. The quenching constants and thermodynamic parameters used to calculate the binding power and the number of binding sites. The binding distance was mensurated by the Forster’s non-radiation energy transfer theory. The conformation of LYS was analyzed by CD spectroscopy and FT-IR spectroscopy, the results indicated that conformation of LYS changed with the addition of CA, and the content of the a-helix was incresead, the conformation was more tightly linked. In the end, the effect on the activity of LYS was studied after treated by CA. We found that CA can increase its enzymic activity.In the third part, study on the interaction between serum proteins and CA. The aim of this study was to examine the interactions of human serum albumin (HSA) and bovine serum albumin (BSA) with CA at physiological conditions. UV-vis, fluorescence spectroscopic and CD methods were used to analyze CA binding mode, the binding mechanisms were almost the same. Thermodynamic parameters analysis showed that CA binded HSA and BSA via electrostatic force. While the fluorescence quenching constant and the numbers of binding site showed stronger binding of CA to HSA. CD spectroscopy indicated CA interaction altered protein secondary structure for both HSA and BSA causing the content of the α-helix was incresead.The forth part, conclutions and prospects.