Study On The Interaction Between Some Small Organic Molecule And Human Serum Albumin

The research of the interactions between human serum albumins (HSA) and various small organic molecules receive great attention in the recent years owing to their great importance in the biomedical, toxicology and pharmacokinetics field. HSA is the main protein in human blood plasma, which can transport and dispose of many endogenous and exogenous compounds. Therefore, HSA has been frequently used as a model protein for investigating the protein folding and ligand-binding mechanism, and it has been an interesting research field of life sciences, chemistry and clinical medicine. In most cases, small molecules interactions at protein binding level will significantly affect the apparent distribution volume of the small molecules. Optical techniques such as fluorescence, ultraviolet-visible (UV-vis absorption) absorption, infrared (IR), and circular dichroism (CD) spectroscopy are powerful tools for studying the ligand-protein interactions under physiological conditions in vitro due to their exceptional sensitivity and speed. In addition, the binding average distance between the donor (Trp-214of HSA) and the ligand can be evaluated according to the Foster’s theory of non-radiation energy transfer.This dissertation consists of four chapters.Chapter1:The structures, functions of proteins and HSA were briefly introduced. The principles of technique used to study the interaction of small organic molecules with proteins were summarized. And the developments of interaction of small organic molecules with proteins were reviewed.Chapter2:The interaction mechanisms between three phthalate plasticizers (diethyl phthalate, dibutyl phthalate, and diisobutyl phthalate) with HSA were studied by fluorescence (steady-state, synchronous and three-dimensional), UV-vis absorption, CD, and IR spectroscopy in combination with molecular modeling under simulative physiological conditions, respectively. The results obtained from fluorescence quenching data revealed that the plasticizers-HSA interaction altered the conformational strcture of HSA. The data of fluorescence resonance energy transfer showed that the existence of energy transfer between three phthalate plasticizers and HSA. The thermodynamic analysis implied that hydrophobic forces were the main interaction for the plasticizers-HSA system.Chapter3:The interaction between three azo dyes (acid orange6, acid orange7, and orange G) and HSA was firstly investigated using nuclear magnetic resonance (NMR) technique in combination with fluorescence, UV-vis absorption, CD, IR spectroscopy and molecular modeling method. The conformational changes of HSA in the presence of three azo dyes were confirmed by synchronous fluorescence, three-dimensional fluorescence, UV-vis absorption, CD, and IR spectra, respectively. The binding distances between three azo dyes and tryptophan residue of HSA were calculated by the efficiency of fluorescence resonance energy transfer, respectively. Molecular modeling showed that three ligands bound within the hydrophobic pocket of subdomain IIA of HSA.Chapter4:The interaction of hydroxyproline (Hyp) with HSA was investigated, firstly, using steady-state fluorescence, synchronous fluorescence, time-resolved fluorescence, UV-vis absorption, CD, and IR spectroscopy in combination with molecular modeling method under simulative physiological conditions. The data of fluorescence quenching spectroscopy indicated that the fluorescence of HSA was quenched by Hyp with a dynamic quenching mechanism. The binding constants were calculated according to Scatchard’s equation and implied that Hyp can bind to different binding sites on HSA. The microenvironment around tryptophan and tyrosine residues and the conformational structure of HSA were confirmed by synchronous fluorescence, UV-vis absorption, CD and IR spectroscopy. Furthermore, the thermodynamic analysis implied that hydrophobic forces were the main interaction of Hyp-HSA system.