Study On The Interaction Mechanism Of Three Proteins With Ursolic Acid And Oleanolic Acid

Terpene is a kind of an important extract, which has been used mostly for the anti-virus, anti-cancer and anti-inflammatory application. In this paper, the interactions between ursolic acid/oleanolic acid and three kinds of protein (bovine serum albumin, human serum albumin, bovine lactoferrin) using fluorescent spectra, UV-Vis absorption spectra and attenuated total reflectance Fourier transform infrared spectroscopy were studied. The binding parameters, the thermodynamic parameters and the effect of certain metal ions on the interactions were studied in detail, and the interaction mechanisms were discussed. The present work consists of the following six parts:1. The main research contents, methods, theoretical models and recent research progress of the interaction of natural forestry drugs and proteins have been briefly reviewed.2. The interactions of ursolic acid/oleanolic acid and proteins (bovine serum albumin, human serum albumin, bovine lactoferrin) using fluorescent spectra were studied. It was found that the fluorescence of protein was efficiently quenched by these drugs by using the protein as an intrinsic fluorescence probe. The binding parameters between the drugs and proteins were discussed, and the results indicated that the binding between the drugs and proteins are strong and effective.3. The change of microenvironment of tryptophan residues in protein and the secondary structure conformation of protein in the absence and presence of two drugs were investigated by using synchronous flourimetry,“phase diagram”method of fluorescence and attenuated total reflectance Fourier transform infrared spectroscopy. It was found that the microenvironment of tryptophan residues and contents of alpha helices, beta sheet and beta turn in the secondary structure of protein were all changed. The polar and hydrophobic of microenvironment of tryptophan residues were also changed. The unfolding process of proteins affected by drugs conformed to the“all-or-none”pattern.4. The fluorescence anisotropy methods indicated the structure change of proteins was affected by drugs in molecular level. We find that the volume and viscosity of bovine serum albumin increased after the binding with drugs. 5. The binding mechanisms between two drugs and protein were discussed respectively. The effects of molecular structure difference on the binding constants were also analysed. The results indicated that OA can bind proteins stronger than UA, the volume of proteins in OA-protein system is bigger than that in UA-protein system.6. The interactions between drug and proteins influenced by Ni(Ⅱ) and Co(Ⅱ) were discussed. The effects of different ions on the binding constants were also analysed. Because of different electronegativities of different metal ions, their effects acting on drug-protein interactions are also different.