Molecular Level Investigation Of The Structure And Dynamics Of Protein At The Cell Membrane Interface

The interaction of protein and membrane is a scientific issue, which is closely associated with the health of people. Meanwhile, it is also an important frontier scientific problem in the biological interdisciplinary. This interaction plays an important role in the biological activities and functions. For example, the correctly folding of protein on membrane is critical to the physiological function of cells. The studies on the interaction between protein and membrane will aid to understand the mechanism of occurrence and development of the related diseases and hope to provide theoretical guidance for developing new physiological peptide, protein and biological drugs.The interaction between protein and membrane is very complicated, influenced by various physical and chemical conditions. Lacking the systematic research of the effect on the interaction between protein and membrane from the external environment makes people have little knowledge about it. In this dissertation, sum frequency generation spectroscopy (SFG) was used and developed to study the effect of peptide concentration, membrane composition, solvent and salt ions on the membrane-associated protein. Meanwhile, we developed a method to differentiate the interfacial protein secondary structure by detecting the signals in fingerprint region. Basic on this method, the dynamic effect of Hofmeister ions on the interaction between melittin and membrane was studied. The dissertation contains six chapters.Chapter1introduces the importance and the present research situation of the interaction between protein and membrane. In this chapter, the research application of SFG on the interaction of protein and membrane is summarized. Then the research content and significance of this dissertation is introduced briefly.Chapter2studies the effect of protein concentration on the interaction between protein and membrane. Prion118-135is taken as a model peptide. The molecular process of prion protein structural transition from normal structure to the abnormal form is obtained depending on the protein concentration.Chapter3discusses the charge of lipid, solvent, peptide concentration influence on the interaction between protein and membrane. As a model protein, Prion106-126prefers to interact with the negatively charged lipid bilayer. The solvent polarizability of peptide solution doesn’t change the structure of peptide on membrane at low peptide concentration. The increase of peptide concentration contributes to the blue shifted of peak centers of peptide.Chapter4studies the influence of ion concentration and ion species of Hofmeister series on the interaction between protein and membrane. In this section, melittin is taken as a model protein. In pure water, the driving force of the interaction between melittin and membrane is hydrophobic matching rather than coulomb interaction. In addition, melitttin partially inserts into the membrane from the result of partition experiments.Chapter5introduces the method to differentiate the interfacial protein secondary structures by detecting the signals in fingerprint region. The Amide Ⅲ signals of a-helix and random coil were detected by this method, which can’t be obtained by other convention methods. The characterization problem of distinguishing random coil and α-helix structure of interfacial protein was solved by combining the amide Ⅰ and amide Ⅲ spectral signals.Chapter6further studies the influence of ion concentration and ion species of Hofmeister series on the interaction between melitttin and membrane by Amide Ⅲ signals. In the presence of ions, the decrease of SFG intensity of melittin on gel phase membrane results from the quantity change of melittin in membrane.