Studies On The Interaction Of Two Kind Of Ionic Liquids With Lysozyme

Interest in ionic liquids, a new type of green solvents, is increasingrapidly. Ionic liquids have the characters of inonic and origanic liquids.Lysozyme has two structure domains,129amino acid residues,molecularweight only14.4KDa, So lysozyme is often used as model to study thestructure of protein.In this paper,We use FT-IR，2D-CO IR，UV，CD and Fluorescencespectrum to learn the interaction of ionic liquids with lysozyme, from differentaspects. As a kind of enzyme,we also can learn the interaction by measure thelytic activity of hen egg white lysozyme.In the studies of lytic activity of hen egg white lysozyme,We haveconsidered the influence factors of pH, ionic liquid types and theconcentration of ionic liquid. We determine the optimal pH=6.23andpH=5.02and choose two kinds of water-soluble ionic liquid [Bmim][otf] and[Bmim][BF₄], the best concentration the150mM.In FT-IRexperiment, We have three reaction system （1） H-D exchange oflysozyme in different pH value buffer solution.（2） H-D exchange of lysozyme in different pH value buffer solution. with the [Bmim][otf].（3） H-Dexchange of lysozyme in different pH value buffer solution. with the [Bmim][BF₄] Respectively using FT-IR,Second derivative spectra, The differencespectrum,2D correction infrared spectrum to study the interaction oflysozyme and ionic liquid and find the amino acid residues and secondarystructure changes. the study found that the different pH value and ionic liquidtypes, the secondary structure change order the αhelix and βsheet is not thesame, Combined with lysozyme activity experiment, The studies found thatsuch a change order with lysozyme activity has certain relevance, and aminoacid residues Arg and Unorder structure have a stronger interaction withionic liquid.In the studies of fluorescence spectrum,We have two reaction system.（1）The fluorescence spectum of lysozyme with the quenches agent[Bmim][otf].（2）The fluorescence spectum of lysozyme with the quenchesagent [Bmim][BF₄].Though the Stern-Volmerplots, We can indicated that theprobable quenching mechanism of fluorescence lysozyme by [Bmim][otf] isstatic quenching but the probable quenching mechanism of fluorescencelysozyme by [Bmim][BF₄] is a mixed quenching of dynamic quenching andstatic quenching. According to the thermodynamic parameters（ΔHå'ŒÎ”S）calculated from the Van’t Hoff equation.We can obtain the information oftypes of noncovalent interactionsthat could play a role in ligand binding toproteins. And the study of Synchronous fluorescence spectroscopy,There was a conclution that ionic liquids are closer to trytophan residues compared totyrosine residues.