Modulation Factors And Application Of Lysozyme Amyloid Fibrillation

Amyloid fibrillation is a unique protein aggregation behavior.Under certain conditions,proteins and peptides will form aggregates in the form of insoluble fibers.Many scientists paid more attention on the research of amyloid fibers which closely related to more than 50major human diseases such as Alzheimer’s disease,Mad cow disease,Parkinson’s disease and diabetes.In addition,amyloid fibers can be prepared to nanomaterial of various styles such as nanosheet and nanosphere,or form composite material with other substances to achieve better performance.Therefore,amyloid fiber has shown good prospects in the field of nanomaterial.These factors are making domestic and foreign scientific researchers increase enthusiasm for amyloid fibrillation research.In view this,studying the mechanism of amyloid fibrillation is of great significance for the treatment of amyloid diseases and the development of new biomaterial is based on amyloid fibers.The first work of this thesis is studied the modulation influence of Hofmeister anion and cation series on lysozyme amyloid fibrillation,and the second work studied the morphology effect of mature lysozyme amyloid fiber by graphene oxide（GO）,and antibacterial application of GO-fiber composite formed by the two.The amyloid fibrillation of lysozyme protein is closely related to the pathogenesis of Alzheimer’s disease.The structural and functional characteristics of hen egg white lysozyme protein are very similar to human lysozyme,and it is often used as a model to research the prevention and treatment of amyloid diseases.In the part of the modulation influence of Hofmeister anion and cation series on lysozyme amyloid fibrillation,this work is mainly used Thioflavin T（Th T）fluorescence spectroscopy,Fourier transform infrared（FTIR）spectroscopy and atomic force microscopy（AFM）to carry out Hofmeister anion and cation series(Hofmeister cation series:NH₄⁺>K⁺>Na⁺>Cs⁺>Li⁺>Rb⁺>Mg²⁺>Ca²⁺>Ba²⁺;Hofmeister anion series:SO₄^2->F^->COO^->Cl^->NO₃^->Br^->I^->Cl O₄^->SCN^-)research on the correlation regularity with lysozyme amyloid fibrillation.Detailed Th T spectroscopy techonology investigations indicated that all ions promoted lysozyme amyloid fibrillation,and the anion series affects the speed of fibrillation basically in the same order as the Hofmeister series;by using FTIR spectroscopy characterization analysis it is found that the content ofβ-sheet structure of amyloid fibers generated under the influence of cations,which is not much different,while the order ofβ-sheet structure content of amyloid fibers generated under the influence of anions sort from most to least is basically the same as that of the reverse Hofmeister series;through AFM technology research,we discovered in this research for the first time that Hofmeister anion series have significant different influence in the microscopic morphology of lysozyme amyloid fibers.SO₄^2-,F^-,COO^-can induce amyloid fibers to show some novel morphological changes,the characteristic of these changes is that the fibers appear branching and thickening,and the fibers affected by Cl^-,NO₃^-,Br^-,I^-,Cl O₄^-,SCN^-are public long fibers.We consider that the reason of two different anions influence in morphological is due to the different dominance of the primary nucleation and secondary nucleation of the amyloid fiber process.In addition,the AFM image shows that different cations have no modulation effect of fibers morphology,because the lack of electrostatic attraction between the positively charged lysozyme protein and the cations.In the research on the effect of graphene oxide on mature lysozyme amyloid fiber and its application,Graphene oxide（GO）effectively decomposes mature lysozyme amyloid fibers,the complex of the two used to against E.coil,and it shows excellent antibacterial consequence.The antibacterial efficiency is better than that of GO or lysozyme alone.We found GO has a significant modulation influence on fiber morphology by using AFM technology analyze combined with Fiber app and NOVA software;different result of FTIR about lysozyme amyloid fiber amide I belt shows the content of lysozymeβ-sheet structure changed obviously.Th T fluorescence techonology analysis indicated that the amyloid fibers content is reduced in the solution by GO.The composite material formed by GO and lysozyme amyloid fibers was subjected to the E.coil antibacterial experiment,and the antibacterial efficiency of the complex can reach more than 80%,which is an excellent E.coil inhibitor.Through FTIR and chemometrics we analyzed the mechanism of the complex and its constituents alone with E.coil.The difference in fingerprint spectra indicates that the secondary structure of bacterial proteins and bacterial cell membrane lipopolysaccharides are affected.Our study believes that the difference in the morphology of the antibacterial agent and the contact method of the E.coil are the main reason for the different antibacterial efficiency of the complex and the individual components.A variety of experimental characterizations are used in this work to study the modulation factors and applications of lysozyme protein fibrillation.We hope that the research results can affect the modulation direction of amyloid fibrillation salt effect,and the development of new nanomaterials is based on amyloid fibers directions which could provide new references.