Study On The Effect Of Ionic Liquids On The Solution Structure Of Lysozyme

As a new type of environmentally friendly organic "green solvents", Ionic liquids(ILs) have a broad application prospect in many fields because of its unique fine properties. Nowadays, ILs have been applied well in protein crystallization, but the study of ILs on how to affect the protein solution structure is rare. Lysozyme is one of the most commonly used model protein, therefore, we choose lysozyme as the research subject in this thesis to investigate the regulation of four imidazole-based ionic liquids on lysozyme solution structure. The thesis is divided in three parts as followed:1. The solubilities of lysozyme in the PBS water and the heavy water solution were measured by ultraviolet spectrophotometer method to investigate the effect of 1% and 5% four ILs on the lysozyme solubility, respectively. The solubility data were associated by the Apelblat experiential equation and the dissolving enthalpies were calculated. The experimental results showed that [BMIM]BF4 and [BMIM]Cl increased the solubility of lysozyme, and [BMIM]Br had no significant effect on lysozyme solubility, while [DMIM]I reduced the solubility of lysozyme. The effect of ILs on solubility can be attributed to changing interaction among lysozyme molecules. Either repulsive interactions are induced or attractive interactions are reduced among lysozyme molecules with [BMIM]BF4 and [BMIM]Cl added. Attractive interactions are enhanced after adding [DMIM]I. while with the presence of [BMIM]Br, the minimum effect on molecular interactions is introduced.2. On-line infrared system was used to study the effect of 1% and 5% four ionic liquids on the secondary structure of lysozyme in heavy water solution in the rise process of supersaturation. The relative percentage of the secondary structure were calculated by the second derivative spectra and Fourier deconvolution spectra combined with curve fitting method to study the reciprocal transformation between the four secondary structure. In the buffer solution without IL, ?-helix and ?-strand changed to ?-turn reversibly with the increase of supersaturation. After adding [BMIM]BF4, only ?-helix changed to ?-turn reversibly, while ?-helix changed to random structure reversibly in the solution with [BMIM]Cl added; When [BMIM]Br was added in the heavy water solution, ?-helix changed to ?-turn irreversibly. The four secondary structure didn't change obviously in the solution with [DMIM]I. The related research has rarely been reported3. The effect of 1% and 5% four ionic liquids on the secondary structure of lysozyme in 0.1mol/L pH 5.01 PBS at room temperature were studied by circular dichroism. The results revealed the transformation process of secondary structure of lysozyme in the dilute PBS with the ionic liquids added at room temperature. The effect of ionic liquids on the secondary structure of lysozyme in the solution provides critical information and important guidance to the research of nucleation assembly and change of activity of lysozyme.