Preparation Of Thin Layer Of Collagen Peptide And Regulation Of Its Surface Properties

The research in this thesis provides research ideas for solving the structural control problems in the process of macromolecular reactions.The content of this thesis is divided into three parts:1-the effect of factors such as the concentration of collagen peptides,the type and amount of surfactants on the behavior of the peptide solution;2-the preparation of collagen peptide monolayers by electrostatic self-assembly technology,and the regulation of the peptide molecule conformation at the interface,to study the relationship between the secondary structure of peptide molecules and the exposure of functional groups to regulate the surface properties of the membrane;3-to graft epoxy polysiloxane to determine the molar grafting ratio and to preliminary explore the intramolecular/intermolecular interaction of polymer molecules on the peptide monolayer influence of phase structure and performance.The main findings are as follows:?1?The contents of this study first adjusted the peptide concentration from 1 to 5%wt?interval concentration 1%wt?and studied the effect of the peptide concentration on its molecular secondary structure;Anionic surfactants were added?sulfate type,alkyl chain length is 6,8,9,11,12,14,16;sulfonate type,alkyl chain length is 12,14?.The effects of alkyl chain length and surfactant amount on the secondary structure of peptide molecules were studied.The secondary structure of the peptide molecule in the solution was determined by circular dichroism chromatography?CD?and the thermodynamic parameters of the system were calculated by conductivity and surface tension methods.Gibbs free energy??G_M^°?,enthalpy??H_M^°?,entropy??S_M^°?,and binding energy difference??E?,were determined to find out the correlation between the free energy of the system and the secondary structure of the peptide.The results showed that the head group and alkyl chain length of the surfactant interfered with the equilibrium conformation of the peptide molecule and the increase of the alkyl chain length promoted the stability of the system.The hydrophobic interaction between the peptide and sodium tetradecyl sulfonate?STSo?is more benifical to the stability of the system.The absolute value of?G is in the order of peptide-sodium tetradecyl sulfonate?G-STSo?>peptide-sodium tetradecyl sulfate?G-STS?>peptide-sodium dodecyl sulfate?G-SDS?>peptide-sodium dodecyl sulfonate?G-SDSo?>Peptide-sodium undecyl sulfate?G-SUS?>peptide-sodium octyl sulfate?G-SOS?.The absolute value of?G in the G-STSo system is the largest.Correspondingly,the?-sheet content in the system is the highest,indicating that the peptide molecular chains in the system are in a relatively stretched state.The decrease of?G,the increase of?S and the increase of binding energy are accompanied by the increase of?-sheet structure content indicating that the polypeptide chain is in a relaxed state.Induction of orderly transformation of the collagen peptide conformation is the basis for regulating the exposure of monolayer primary amino groups.?2?Using the amphoteric polyelectrolyte property of the peptide molecule,the peptide is fixed to the surface of the positively charged substrate by electrostatic self-assembly technology to prepare a peptide monolayer.Atomic force microscopy?AFM?was used to characterize the film thickness and peptide molecular packing morphology;the micro-confocal Raman spectroscopy?Raman?was used to detect the signal changes of the peptide amide?,?,and?bands and calculate?-helix,?-sheet and relative content of each secondary structure;X-ray photoelectron spectroscopy?XPS?was used to determine the element N content and N element valence information on the surface of the monolayer and to analyze the changes in the exposure of primary amino groups on the monolayer surface;Primary fluorescent amino probes were synthesized to assist Laser confocal microscope?LSCM?to determine the primary amino distribution points.Through the above studies,the relationship between the collagen peptide molecular conformation,?G,and surface primary amino group exposure was determined.Furthermore,the stability of the membrane was studied by a fluorescence microscope?FM?,the affinity/hydrophobicity of the membrane was characterized by an interfacial rheometer and the Zeta potential of the membrane surface was measured by a solid surface zeta potential analyzer?EKA?.The results show that as the concentration of SDS and STSo increases from critical aggregation concentration?CAC?to 6%,the Gibbs free energy of the system decreases significantly,and the G-SDS/STSo binding energy increases,which promotes the formation of the?-sheet structure and then induces a reduction in layer thickness.Peptide molecules are densely packed to form nanoparticles.The formation of?-sheet structure fully exposed the primary amino groups on the surface of the nanoparticles and effectively achieved the coordinated regulation of the charged properties of the functional groups and hydrophilic/hydrophobic properties of the surface of the peptide monolayer.The octapeptide cholecystokinin?CCK-8?and Microculture Tetrazolium Assay?MTT?assays and cell cloning experiments showed that the membrane has excellent cell compatibility.?3?The relationship between the peptide molecule conformation and the system energy and the grafting ratio of epoxy polysiloxane was studied systematically;the molar grafting ratio of epoxy polysiloxane was measured using a quartz crystal microbalance?QCM?and XPS.The valence states and relative content changes of N and Si elements after siloxane grafting were measured.The relationship between the secondary structure of peptide molecules and the controllability of epoxy polysiloxane grafting ratio was obtained.The effect of intermolecular/internal interaction between epoxy polysiloxane and peptide on the monolayer structure was studied by AFM and the elemental composition of the monolayer surface was measured by XPS.The secondary structure of the peptide molecule and the graft ratio of epoxy polysiloxane were systematically discussed.The effects of electrostatic,hydrophobic,hydrogen bonding and other interactions between polymers were investigated.The relationship between the grafting ratio of polysiloxane in the graft polymer and its phase behavior was studied.The mechanism of the grafting ratio was changed and the effect of polymer molecular interaction on the membrane structure was studied.The mechanical properties of the monolayers were characterized by AFM and the water contact angle of the monolayer surface was measured to determine the structure-properties relationships of the monolayer.The molar grafting calculation results showed that the more primary amino groups exposed on the monolayer surface,the higher the epoxy grafting ratio.The phase separation structure of the thin film is closely related to the graft ratio and molecular weight of the epoxy polysiloxane.Among G-SDS_6%and G-STSo_6%,when the molecular weight was 1000,the grafting ratio of epoxy polysiloxane was high and there was a strong non-covalent bond between the polysiloxane segment and the collagen polypeptide component.The interaction inhibits self-aggregation of the polysiloxane segments.The two phases present a relatively uniform distribution.The surface roughness of the monolayer was reduced and the ordering of the stacked structure was increased.The formation of a dense,ordered monolayer structure is accompanied by an increase in the film's viscoelasticity,flexibility and hydrophobicity.Epoxy polysiloxane grafting ratio and molecular weight,changes the interaction between components causing regular changes in film surface adhesion and Young's modulus.