Spectrum Studies Of Three Flavonoids Small Molecules To Bovine Serum Albumin Interaction

Serum albumin is the most abundant protein in blood plasma. As the storage and transfer protein for a lot of endogenous and exogenous compounds, it can interact with many drug molecules. Small fiavoind drug molecules are capable of a wide range of pharmacological activities, such as antioxidant, anti-tumor, anti-virus, anti-inflammatory and anti-bacterial, etc. As a result, the research on the interaction between serum albumin and falconoid is extremely significant to the understanding of the absorption, distribution, excretion, pharmacological activity and toxicity of small fiavoind drug molecules in the human body. In this paper, fluorescence spectroscopy, UV-visible absorption spectroscopy and infrared spectroscopy are employed to study the interactions between bovine serum albumin (BSA) molecules and small fiavoind drug molecules, such as apigenin, galangin and genistein. Finally, the mechanism of the interaction between drugs and protein, it's binding constant, binding sites, thermodynamic binding parameters, and combination distance, as well as the impact on the protein conformational change caused by small drug molecule and other environmental factors (such as solution pH value and the metal ion's impact) is demonstrated. The biologically active groups in the interaction between drugs and protein is identified. These findings are of great significance to biochemistry, pharmaceutical science, and clinical medicine. The major contributions of this thesis include:1. The interaction between three small flavoind drug molecules, which are apigenin, galangin and genistein, and BSA is investigated with fluorescence spectroscopy using the drug's quenching on the endogenous fluorescence of serum albumin. The results indicate that effective static quenching process occurred between drug molecules and BSA. The binding site of small drug molecules and BSA is also studied. The combination constant under different temperature is determined. And the main intermolecular force is identified to be the hydrophobic force.2. The conformational change of protein is investigated before and after it's interaction with the three small flavoind drug molecules by using synchronous fluorescence technique, UV-visible absorption differential spectroscopy and infrared spectroscopy. The results show that the hydrophobic nature of the micro-environment where tryptophan residues reside, as well as the secondary structure of protein changed after the combination of proteins, which further indicates the existence of the interaction between the three small flavoind drug molecules and BSA.3. The influence on combination reaction stemmed from pH value and mental ion's presence is fully investigated in this thesis. The result of the impact in turn justified that there is electrostatic force between the interaction between the three small flavoind drug molecules and BSA. The mechanism of these factor's influence is speculated theoretically.4. The combination of the three small flavoind drug molecules with BSA is compared separately from the fluorescence quenching, binding constants and sites, binding capacity, pH value and metal ions. With results gained from the above comparison and. the analysis of the structure of the three molecules, we concluded that the No. 5 and No. 7 phenolic hydroxyl on the A circle of the three small drug molecules are the drug decisive bio-active groups. Experiment shows that the number and position of the hydroxyl on the three flavoind molecules has important influence on their reaction with BSA. The relative interaction strength between the three flavoind compounds and BSA is as follows: apigenin > Galangin > genistein. Considering that the relative hydrophobicity of the three flavoind small molecules is apigenin > Galangin > genistein , which is the same with the interaction strength, it can be concluded that main intermolecular force between the three small drug molecules is identified to be hydrophobic force.