Studies On The Effects Of Novel Surfactants On The Structures Of Bovine Serum Albumin (BSA)

The studies on the interactions of proteins and surfactants are of important theoretical and practical meaning. Firstly, both of them are the substance in common use and the interactions between them exist widely. So we must consider the effect of surfactants on proteins, such as the enzyme catalysis reaction, surface adsorption, capabilities of binding other molecules and forming molecule aggregation of globule albumin, which were used as the functional ingredient of diversiform foods, cosmetics and pharmacy products. Secondly, because different proteins have distinct difference the study results of interaction between proteins and surfactants can not be of universality. Thirdly, with the increasing of the studying and using of new style surfactants such as saccharide-based and fluorinated surfactants, the effects of which on proteins are a blank area. So the studies of these types of works are still very active.In recent years, these researches are focus on three aspects: the structure of the protein-surfactant complexes and the conformation changes of protein, phase behaviors of the protein/surfactant mixture system, interface adsorption of protein-surfactant. In these researches, comparing with that on anion surfactants the studies on interaction between cation surfactants and protein are few. The effects of new surfactants such as saccharide-based and fluorinated surfactants on protein need research deeply. In this paper, we selected bovine serum albumin and studied the effects of one saccharide amide surfactant, one fluorinated surfactant and one cation surfactant on it. This thesis is divided into four parts.In the first section, the importance of the study on surfactant and protein and the study progress on the interaction between surfactant and protein are summarized.In the second section, we studied the interaction between a novel saccharide amide anion surfactant sucrose-(sodium glucose-6-carboxylate)-(sodiumN-dodecyl-fructose-l-carbamide-4-carboxylate) (SDAD) and BSA, at the same time SDS which has the same hydrophobic chain with SDAD was selected to study comparatively. The results of surface tension, conductivity and zeta potential indicate that SDAD has been bound to BSA, and different from SDS, the binding depends on hydrophobic force. The fluorescence spectrum results of SDAD/BSA system indicate that the fluorescence intensity of BSA decreases in beginning then increases with the increase of the concentration of SDAD and at the same time the maximum of emission wavelength shifts form 348nm to 330nm. The CD spectrum results indicate that the percentage ofα-helicity decreases from 44.3% to 31.4%, as theβ-sheet content increases from 21.7% to 32.6%, which indicate that the secondary structure of BSA is disrupted. The dynamic light scattering results indicate that there will be a larger R_h distribution besides the R_h 4.6nm which is the R_h of BSA with the join of surfactants. And the larger R_h distribution shifts to more large with the increasing of surfactants concentration until the R_h reachs to near 1100nm. It appears another R_h distribution when the binding of surfactants to BSA reaches saturation and that is the R_h of surfactant free micelles. Both SDS and SDAD have the same results, which indicate the conformational changes of BSA. The Negative-staining TEM results of SDS/BSA system indicate the conformation changes of BSA with the increasing of SDS concentration, and we observed the "necklace and bead" structure at high SDS concentrations. Different from SDS, the SDAD/BSA mixture systems present a communion structure under negative-staining TEM.In the third section, the interaction between sodium perfluorooctanoate (SPFO) and BSA has been studied, at the same time sodium octanoate (SO) was selected to study comparatively using conductivity, zeta potential, fluorescence spectrum and CD spectrum. The results of conductivity and zeta potential indicate that SPFO has been bound to BSA. The fluorescence spectrum results of SPFO/BSA system indicate that the fluorescence intensity of BSA decreases in beginning then increases with the increasing of the concentration of SDAD and at the same time the maximum of emission wavelength shifts form 348nm to 330nm. The CD spectrum results indicate that the percentage ofα-helicity decreases from 44.3% to 31.4%, at theβ-sheet content increases from 21.7% to 32.6% as the concentration of SPFO reaches 1mM, indicating that the secondary structure of BSA disrupts. The fluorescence and CD spectrum results indicate the change of BSA conformation induced by SPFO. In the fourth section, the interaction between cation surfactant TTAB and BSA has been studied using surface tension, conductivity, zeta potential, fluorescence spectrum, CD spectrum and DLS. The results of surface tension, conductivity indicate that TTAB has been bound to BSA. The fluorescence spectrum results of TTAB/BSA system indicate that the fluorescence intensity of BSA decreases in beginning then increases with the increasing of the concentration of TTAB and at the same time the maximum of emission wavelength shifts from 345nm to 329nm. The CD spectrum results indicate that the percentage ofα-helicity decreases from 45.3% to 19.1%, at the same timeβ-sheet content increases from 22.4% to 38.3%, indicating the changing of BSA secondary structure. The dynamic light scattering results indicate that it has a R_h distribution at 295nm besides the R_h 4.6nm which is the R_h of BSA when the concentration of TTAB reaches 2mM. And the larger R_h distribution shifts to more large with the increasing of surfactants concentration until the R_h reachs to near 1260nm. Another R_h distribution appears when the binding of surfactants to BSA reaches saturation and that is the R_h of surfactant free micelle. The results indicate the conformational changes of BSA.