| The natural polymer by biochemical role or photosynthesis is in the natural, mineral and the formation of a molecular compound. Compared with the synthetic polymer, natural polymer has many advantages, for example, wide variety of sources, renewable, environment friendly, biocompatible and so on. So natural polymer become more and more important in materials.In this paper, we studied two kind of natural polymer, Soy protein isolated and silk protein. Soy protein isolated, with many acidic amino acid residues and alkaline amino acid residues, is the ideal amphoteric ion-exchange membrane material. Herein, two biochemical agents, guandine hydrocholoride (GuHCl) and dithiothreitol (DTT), were used to destroy the hydrogen bonds and disulfide bonds in Soy protein isolated, which were removed by dialysis against water to obtain Soy protein isolated solution with initial concentration of2.5wt%and without obvious degradation. More concentrated Soy protein isolated solutions were obtained by reverse dialysis against PEG solution, we use4.2wt%Soy protein isolated solution in the research. Silica particles were used to generate the pores in the membranes. Epichlorohydrin were used as crosslinking agents. Silica particles were dissolved by40%(w/w) hydrofluoric acid (HF). The time for lysozyme to reach adsorption equilibrium was about5h. Both the protein and the soy membrane are amphoteric, so the charges on their surface vary according to the environmental pH, and as a result the adsorption capacity of the protein on membrane is different at different pH. The maximum adsorption of lysozyme was found at pH9.15, and the adsorption capacity maintained above120mg/mL from pH5.72to pH11.2. Several cycles of adsorption-desorption were performed, The result shows the low desorption ratio and the reusability of the membrane is not very good.The dynamic adsorption behavior of lysozyme and ovalbumin on Soy protein isolated membrane was also investigated. The dynamic adsorption of individual protein on3Soy protein isolated membranes was carried out by loading0.25mg/mL protein solution at a flow rate of2mL/min. The dynamic adsorption capacity for lysozyme was4.5mg/mL. Keeping other condition unchanged, at a flow rate of4mL/min, the dynamic adsorption capacity for lysozyme was3.9mg/mL. Keeping other conditions unchanged, the Soy protein isolated membranes increased to4, the dynamic adsorption capacity for lysozyme was5.8mg/mL. Keeping other conditions unchanged, using0.5mg/mL protein solution, the dynamic adsorption capacity for lysozyme was6.3mg/mL. The result shows that increasing the flow rate, will reduce the lysozyme dynamic adsorption capacity of Soy protein isolated porous film. But increasing both the number of superimposed membrane and the concentration of the protein solution, will improve the lysozyme dynamic adsorption capacity of Soy protein isolated porous film.we used time-dependent FTIR spectroscopy to obtain the conformation transition kinetics of RSF solution. The conformation transition was induced by four kinds of alcohol, i.e., methanol, ethanol, propanol, and isopropanol. Another organic solvent we chose to induce the conformation transition was acetone. From the time-dependent difference infrared spectra, we obtained the conformation transition kinetics of silk fibroin by the absorbance-time curve of β-sheet formation. The results showed that the conformation transition rate decreased with the increase in the carbon number in alcohol. It was also found the conformation transition taken place faster when induced by acetone than by propanol and isopropanol. Therefore, the conformation transition rate of silk fibroin when induced by difference organic solvent was methanol>were... |
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