Study On The Binding Of Bioactive Molecules And Human Serum Albumin By Spectroscopic And Molecular Modeling Methods

As the essential life substance to biology, protein has a carrying and storage capability in cell. Serum albumin, which is the most abundant and important protein in blood plasma, serves as a transport carrier in delivering all sorts of endogenous and exogenous substances to each organ and part, in order to maintain normal metabolism. Therefore, the investigation on the binding mechanism of small molecules with serum albumin has been a hot spot in research field of life sciences, clinical medicine and chemistry. The study is not only useful for providing information on drugs transport and metabolism in the body, as well as protein conformational transformation, but also can suggest new approaches to drug structure design and improvement so that we can accelerate the discovery of clinical drugs which will maximize response and minimize side effects.In the thesis, fluorescence spectroscopy, ultraviolet-visible spectrum in combination with molecular modeling were employed to study the interaction between four drugs and human serum albumin(HSA) under simulated physiological conditions from structural and energetic aspects. The drugs include 8, 2-S-cyclicguanosine,5-methyl-2’-deoxycytidine,(E)-2-((1,4-dihydrxy-9,10-dioxo-9,10-dihydroanthracen-2-yl) methylene)-N-(4-methoxyphen-yl) hydrazinecarbothioamide and(E)-N’-((1,4-dihydroxy-9,10-anthraquinone-2-yl) methylene)-2-hydroxybenzohydrazide. Five parts were contained in this dissertation.Chapter 1. The structures and functions of proteins were described. A brief introduction was given to the recent advances in the study on the interactions between small molecules and protein, including research methods, contents, the current situation and their respective advantages and disadvantages.Chapter 2. Under simulative physiological conditions, by using fluorescence spectrum, ultraviolet-visible spectrum in combination with molecular modeling, the interaction between 8, 2-S-cyclic guanosine and HSA was investigated. The spectroscopic results indicated that 8, 2-S-cyclic guanosine can quench the fluorescence of HSA with a static mode; The binding distance between 8, 2-S-cyclic guanosine and tryptophan residue in HSA was calculated according to the F?rster energy transfer theory, which estimated that the binding was related to the fluorescence resonance energy transfer. The effect of 8, 2-S-cyclic guanosine on the conformation of HSA was analyzed by the synchronous fluorescence spectroscopy and molecular modeling.Chapter 3. The interaction mechanism of 5-methyl-2’-deoxycytidine and HSA was investigated by fluorescence spectroscopy in combination with molecular modeling in pH 7.4 condition. According to the data of fluorescence spectra, the binding constants, the kind of binding force were calculated and discussed. The effect of 5-methyl-2’-deoxycytidine on the conformation of HSA was analyzed by the synchronous and three-dimensional fluorescence spectroscopy. Meanwhile, molecular modeling method was used to predict the interaction from molecular level. The results of molecular modeling were in agreement with the experiments.Chapter 4. The interaction between(E)-2-((1,4-dihydrxy-9,10-dioxo-9,10-dihydroanthracen-2-yl) methylene)-N-(4-methoxyphen-yl) hydrazinecarbothioamide(EN) and human serum albumin was studied in a simulated physiological condition by spectrometry methods and modeling technology. The mechanism of the interaction was studied. The structure change of human serum albumin in the absence and presence of EN was discussed. Furthermore, the result of molecular modeling suggested EN might locate in the hydrophobic cavum of human serum albumin.Chapter 5. Using fluorescence spectroscopy in combination with molecular modeling, the interaction between(E)-N’-((1,4-dihydroxy-9,10-anthraquinone-2-yl)methylene)-2-hydroxybenzohydrazide(ENH) and human serum albumin was studied under simulative conditions. By non-radiation energy transfer theory and fluorescence quenching, the quenching mechanism was studied. The thermodynamic parameters and the interaction forces between ENH and human serum albumin were discussed.The effect of ENH on the conformation of HSA was analyzed by the synchronous, three-dimensional fluorescence spectroscopy and molecular modeling.