| Proteins are the material base of life, which take on diversified physiological function. Proteins are the carrier of many physiological functions, and are also the direct expresser of physiological characters. It is very important for researchers to expound the secrets of life on molecular lever to further penetrate the interaction mechanism between small molecules and protein, especially to develop rapid and convince assay for proteins. This project is the forward position and hot point in biochemical and biophysical researches.For the seek of the new spectrum probes of protein and researching the interaction of protein and small molecules, this thesis studied the interaction mechanism between protein and small molecules using the research techniques including fluorescence, RLS, surface tension, UV absorption, circular dichroism (CD) spectrometries and transmission electron microscop (TEM). Some rapid, accurate and handy assays were developed for protein. This thesis is written in five sections.In the first section, we summarized the structure and character of protein, the research method and evolution of protein with small molecules, the principle of RLS method and the recent developments of RLS probe for BSA. 147 references are cited here.In the second section, the interaction between florasulam (FU, 2',6',8-trifluoro -5- methoxy [1,2,4] tria -zolo [1,5-c]pyrimidine-2-sulfonanilide) and bovine serum albumin (BSA) was investigated by fluorescence, UV absorption and CD spectrometries. A strong fluorescence quenching was observed and the quenching mechanism was considered as static quenching according to the Stern-Volmer equation. The binding constants of FU with BSA at 299K and 309K were obtained as 1.5×104 and 7.1×103 L mol-1, respectively. There was a single binding site between FU and BSA. The thermodynamic parameters enthalpy change (△H) and entropy change (△S) were calculated as -57.89 kJ mol-1 and -113.6 J mol-1K-1 respectively, which indicated that the acting force between FU and BSA were mainly hydrogen bond and Vander Waals force. According to the Forster non-radiation energy transfer theory, the average binding distance between donor (BSA) and acceptor (FU) was obtained (r=1.6nm). The investigations of the UV/Vis and CD spectra of the system showed that the conformation of BSA was changed in presence of FU.In the third section, the interactions between congo red (CR) and bovine serum albumin (BSA) were studied in different conditions in the presence of non-ionic surfactant Triton X-100 (TX-100) using fluorescence, fluorescence lifetime, UV absorption and CD spectrometries. The fluorescence of BSA was quenched by CR-TX-100. The quenching mechanisms were considered as static quenching in both physiological and a Na3C6H5O7-HCl buffer solution. The interaction mechanism was thought that TX-100 facilitates the interaction between CR and the protein, and a large complex was formed. The investigation of the CD spectra of the system showed that the conformation of BSA was changed by CR-TX-100.In the forth section, a new resonance light scattering (RLS) assay of proteins such as bovine serum albumin (BSA), human serum albumin (HSA) and egg serum albumin (EA) was presented. In the medium of hexamethylenetetramine (HMTA)-HCl (pH=5.40) buffer, the RLS of Y3+- sodium dodecyl benzene sulfonate (SDBS) system could be greatly enhanced by protein. The enhanced intensity of RLS at 355 nm was in proportion to the concentration of proteins in the range of 4×10-8 -5.0×10-6g mL-1 for BSA, 4.0×10-8- 5.0×10-6 g mL-1 for HSA and 8.0×10-8-2.0×10-5 g mL-1 for EA. Their detection limits were 1.0×10-8, 1.1×10-8 and 5.9×10-8 g mL-1 (S/N=3), respectively. Samples were determined satisfactorily.In the fifth section, we found that there were interactions among organic solvent (acetone or ethanol), SDBS and protein. It was found that in the citric acid-K2HPO4 buffer (pH=2.5 for acetone system and pH=3.4 for ethanol system), the weak resonance light scattering (RLS) of acetone-SDBS (or ethanol-SDBS) was enhanced greatly by the addition of protein. The enhanced RLS intensity was in proportion to the concentration of protein. The detection limits for BSA, HSA and EA were 2.3×10-8 , 2.5×10-8 and 2.0×10-8 g mL-1 (S/N=3) in acetone system and were 8.0×10-8-1.0×10-5 8.0×10-8-1.4×10-5 and 1.0×10-7-1.0×10-5 g mL-1 in ethanol system, respectively. Actual sample, i.e., HSA was determined satisfactorily, and the RSD of acetone system and ethanol system were 1.4% and 3.5%, respectively. In my opinion, the organic solvent could facilitate the interaction between SDBS and the protein, and a large complex was formed, which resulted in the enhancement of RLS.The chief characteristics of this thesis are as follows:(1) In this thesis, we studied the interaction mechanisms between BSA and small organic moleculars such as a new triazolopyrimidine sulfonanilide herbicide florasulam and a bisazo dye congo red using fluorescence, fluorescence lifetime, UV absorption and CD spectrometries, which enriched the research in the fields of herbicide and dye.(2)The RLS enhancement of system of organic solvent (or the rare earth ions) with protein in presence of surfactant SDBS was studied, which was utilized to determine proteins. The method was simple, rapid and had a wide concentration linear range. Several instruments were used to study the interaction mechanism of the system such as fluorescence, UV absorption and CD spectrophotometer and TEM.
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