Study On The Mechanism Of Interaction Between Small Drug Molecule Ginsenoside Rd And Bovine Serum Albumin

In this thesis, the interaction betweenbovine serum albumin and Gensenoside Rd has been studied by fluorescence spectroscopy, three dimensional fluorescence spectra, synchronous fluorescence, UV-vis absorption and circular dichroism(CD) techniques under physiological p H condition, along with computer molecular simulation. The mechanism of the interaction between Gensenoside Rd and bovine serum al bumin, including quenching mechanism, binding sites, binding constants, binding force types, and the changes of protein structure were investigated. This thesis is divided into four chapters as follows:The first chapter of the thesis summarizes the struct ure, biological function and properties of both Gensenoside Rd and bovine serum albumin, introduces the research techniques and methods of interaction of small molecular drug with proteins, and then proposes the content and significance of this paper.The second chapter investigates the bonding behavior of Gensenoside Rd to bovine serum albumin using fluorescence spectroscopy and non-radiation energy transfertheory. The experimental results show that Gensenoside Rd can quench the endogenous fluorescence of bovine serum albumin, and the endogenous fluorescence quenching type is the combination of static and dynamic quenching, namely the combinedquenching process because of the formation of the drug-protein complex.Bovine serum albumin has only one Gensenoside Rd-binding site. The thermodynamic analysis suggests that hydrophobic interaction is the main force between bovine serum albumin and Gensenoside Rd, and the interaction is drived by enthalpy. According to the theory of Fo?rster's non-radiation energy transfer, the binding distance between bovine serum albumin and Gensenoside Rd is calculated to be 2.49 nm, which further proves that the quenching of bovine serum albumin endogenous fluorescence by Gensenoside Rd is a combined quenching process including static quenching.The third chapter of the thesis explores the conformation changes of bovine serum albumin induced by Gensenodie Rd by use of synchronous fluorescence spectrum, three dimensional fluorescence spectrum, UV-visible spectra and circular dichroism. The results obtained from synchronous fluorescence spectroscopy and three-dimensional fluorescence spectrum experiment show that increase of the concentration of Gensenoside Rd can change the microenvironment of tryptophan in bovine serum albumin strongly, while the microenvironment of tyrosine does not change significantly. The UV-vis spectroscopy experiment indicates that Gensenoside Rd can bind to the protein and form a drug-protein complex, then loose the peptide chain of protein. Based on the circular dichroism spectrum experimental data, the secondary structures of the protein before and after the addition of Gensenoside Rd are calculated using software CDNN.The fourth chapter mainly uses computer simulation technology to study the docking between Gensenoside Rd and bovine serum albumin, and to calculate the front molecular orbits of Gensenosides Rd. The molecular docking simulation results show that Gensenoside Rd can combine to bovine serum albumin residues(Trp-213) around its active pocket, decreasing the fluorescence intensity of endogenous protein luminophore, and the sugarmoieties base is the position for Gensenosides Rd to combine tobovine serum albumin. Also, the calculated frontier molecular orbits of Gensenoside Rd including HOMO and LUMO can be used to well explain the results from molecular docking.