Study On The Interaction Between Several Min-molecules And Serum Albumin

Serum Albumin (SA) is the most abundant carrier protein in blood circulation. It has many important physiological and pharmacological functions, which can bind many exogenous and endogenous ligands in blood, and realize transport and distribution of many molecules and metabolites, such as fatty acids, amino acids, bilirubin, hormones and many diverse drugs. Therefore, it has been one of the most extensively studied of all proteins. Investigating the binding mechanism of toxic materials and drugs with SA has many importances in toxicology and pharmacokinetics. Thus, it has been an interesting research field of life sciences, chemistry and clinical medicine. In this dissertation, on the basis of the previous research, the fluorescence spectroscopy combined with UV-visible absorption spectroscopy, Fourier transform infrared (FT-IR) spectroscopy and computational modeling were used to investigate the interaction of several small molecule substances with SA. The following major innovative works were carried out:1 .Several methods were associated to study the interaction of diphacinone and three components of small molecules (heteropoly salt (PM-19), 4-nitroaniline and hexaflumuron) with bovine serum albumin (BSA) and human serum albumin(HAS). The binding properties including the fluorescence quenching mechanisms, binding constants and the number of binding sites were investigated in detail, thermodynamic parameters were calculated, and the main interaction force between drugs and proteins was discussed.2. The cause of departure from the Stem-Volmer plots at different conditions was analyzed.3. The effects of drugs on SA second structure were investigated with FT-IR techniques.4. The computational modeling method was used to study the drug-SA interaction and the study results were in consistent with the experimental results.This dissertation consists of five chapters:Chapter1:The structures, functions and of proteins were briefly introduced. The contents and methods of interaction of different kind of small ligands with protein were reviewed.Chapter2: Under the imitated physiological condition of animal body, the interactions of heteropoly salt (PM-19) with serum albumin (SA) were investigated by fluorescence spectrum and absorption spectroscopy. It was shown that this compound had a quite strong ability to quench the fluorescence launching from SA. we found that SA had reacted with PM-19 and formed a certain new compound. The quenching belonged to static fluorescence quenching. Based on F?rster's non-radiation energy transfer mechanism, the binding locality (r = 4.14nm) was calculated between donor and accepter. The effect of PM-19 on the conformation of BSA was analyzed by synchronous fluorescence spectroscopy.Chapter 3: the interaction between 4-nitroaniline and serum albumin (SA) has been studied by fluorescence spectroscopy, absorption spectra, synchronous fluorescence and three dimensional fluorescence spectra. A strong fluorescence quenching reaction of 4-nitroaniline to SA was observed and the quenching mechanism was suggested as static quenching and non-radiation energy transfer. In addition, for BSA, at higher ligand concentration, the Stern-Volmer plot exhibits an upward curvature, concave towards the y-axis. It illustrated both dynamic and static quenching was involved. Furthermore synchronous fluorescence spectra showed that the binding sites for 4-nitroaniline is close to tryptophan residue of SA. It is also indicated that the polarity around the tryptophan residues were decreased and the hydrophobicity was increased. The three dimensional fluorescence spectra proved that 4-Nitroaniline destroyed ordered structure of SA, resulting in formation of more folding of SA.Chapter 4: the interaction of hexaflumuron with Bovine serum albumin was investigated by fluorescence spectroscopy at different temperature respectively. It was found that the intrinsic fluorescence can be quenched by hexaflumuron and it is Static quenching. Furthermore synchronous fluorescence spectra showed that hexaflumuron destroyed ordered structure of BSA, resulting in formation of unfolding of BSA. Infrared spectral results revealed that the binding of hexaflumuron induced conformational changes in BSA, resulting in the decrease of a-helical.Total conclusions were given in the fifth chapter.