The Structural Transition And Controlled Release Of Lysozyme Interacted With The Polyelectrolyte Of Different Hydrphobicity

Recently, many research has focused on the interactions between protein and polymer. Protein is a kind of non-periodical polymer. Noncovalent bond interactions, featured by hydrogen-bonding, electrostatic, hydrophobic, and van der Waals interactions that exist inside and outside protein, are very important for the native structure of protein. The interactions of globular proteins with oppositely charged polymers can form soluble complexes, coagula, or precipitates, depending on the concentrations of protein and polymer, pH and ionic strength of aqueous solution. At present, most research focus on the polymer-protein complex stabilized by electrostatic interaction. Although the electrostatic interaction has little impact to the structure and activity of the proteins in the complex and makes the protein easier to release from the complex, the stabilization of the complex is weak, compared with the complex stabilized by the hydrophobic interactions. Therefore, we use the polymer which includes the hydrophobic side chain or block to adjust the interaction between the polymer and lysozyme and form the stable polymer-protein particles by controlled electrostatic and hydrophobic interactions. And we also achieve the reversible recovery and controlled release of lysozyme.The first part of the thesis is to utilize the light scattering, circular dichroism, absorption spectroscopy to characterize the structure and activity transition of lysozyme on interacting with and releasing from poly(isobutylene-alt-maleic acid) (PIMA) and poly(1-tetradecene-alt-maleic acid) (PTMA). At pH 7.4, the interaction of PIMA with lysozyme can only partly disturb the tertiary structure of lysozyme, while PTMA has very intensive influence on the structure of lysozyme, that is, the hydrophobic interaction between PTMA and lysozyme completely destroy the native structure and activity of lysozyme. Adding NaCl and GdHCl can release of lysozyme from the complexes with the copolymers; released lysozyme recovers its native structure and activity.The second part of the thesis is about the formation of the complex made up with the (sodium (sulfamate-carboxylate)isoprene/ethylene oxide double hydrophilic block copolymers, SCIEO) and lysozyme and the release of lysozyme from the complex. The complex particle of lysozyme and SCIEO has good dispersion in aqueous solution. The second structure and tertiary structure of the lysozyme influenced by the polymer in the complex, and the activity is only 20% or so. NaCl at some concentration can dissociate the SCIEO-lysozyme complex by screening the electrostatic interaction. Lysozyme released from the complex can recover its native structure and activity. The results of release in vitro under physiological pH and ionic strength reveal that the release of lysozyme has relationship with the sampling frequency not the sampling interval. The results also confirm that there is a balance between the complex particles and lysozyme, when the amount of lysozyme decreases, the balance will be rebuilt with partly dissociation of the complex.Our research indicates that the polymer-protein complex formed by hydrophobic interaction is more stable with completely lost of protein structure, while the lysozyme released from the complex can still recover its native structure and activity. This conclusion is helpful for the application of synthetic polymer in protein separation and purification, protein immobilization and stabilization, protein folding, and protein encapsulation and controlled release.