| Recently, the researches of peptidomics have gained a great development, aiming at analysing endogenous peptides and small molecular proteins qualitatively and quantitatively at specific times and places in organisms. Endogenous peptides are the messengers of information transmission among cells. And the endogenous peptides can transport information delicately through endocrine and other ways to regulate the vital processes of growth, development, reproduction, metabolism, behavior and etc.There are many studies indicating that endogenous peptides are a kind of important potential disease markers. Therefore, the researches on analysis of endogenous peptides/peptidomics are of great practical significance and scientific significance in diagnosis of clinical disease.There are still many major scientific difficulties on the researches of peptidomics at present. For example, biological samples are easily contaminated by salts; some materials including macromolecular proteins and high abundance moleculars have strong interference signal on mass spectrometry analysis of endogenous peptides. So, finding the appropriate research methods to avoid these adverse factors has become a research hotspot and difficulty on peptidomics. The development of novel properties of nanomaterials for separation and enrichment of endogenous peptides selectively has become a hot area of research on peptidomics currently. These technologies are characterized by simpleness, efficiency and fast performance.This thesis carries out serials of scientific efforts to design and synthesize graphene related materials by utilizing physical and chemical properties of graphene, including2D large surface area and high mechanical strength for the difficulties of researches on peptidomics. And these novel composites mateirials have been developed into efficient means of separation and enrichment of endogenous peptides on peptidomics. Focusing on the subject of selective enrichment methods of low abundance endogenous peptides by using graphene based materials, this dissertation is divided into four chapters.The first chapter mainly summarizes the development history and current research progress in proteomics and peptidomics. The importance of researches on proteomics and peptidomics is interpreted specifically. Furthermore, this chapter reviews the latest pretreatment technology and identification technology on the researches of proteomics and peptidomics. The excellent properties of graphene and the prospect of application on the researches of peptidomics are introduced concretely. And finally, the purpose and significance of the thesis topic is put forward in the chapter.The second chapter introduces a facile synthesis method of a dual-platform composite graphene@SiO2@PMMA possessing double-sided surfaces by coupling sol-gel method with aqueous-phase radical polymerization. Additionally, it enables composite applications to the enrichment of endogenous peptides for mass spectrometric analysis. In this work, the dual-platform graphene@SiO2@PMMA material is believed to be a very promising and great potential material, which is of high value for further researches and explorations.The design and synthesis traits of sandwich structured graphene/mesoporous silica composites with C8-modified pore wall are introduced in the third chapter. The sandwich structured graphene/mesoporous silica composite (C8-modified graphene@mSiO2) are synthesized by coating mesoporous silica onto hydrophilic graphene nanosheets through a surfactant-mediated co-condensation sol-gel process. And a series of characterization is carried out successfully. Subsequently, the novel C8-modified graphene@mSiO2materials are applied in enrichment of peptides in complicated environments and to extract the endogenous peptides from the mouse brain tissue. We have successfully synthesized sandwich structured graphene/mesoporous silica composite materials with extended plate-like morphology, good water dispersibility, highly open pore structure, uniform pore size, high surface area and unique C8-modified-interior pore wall through a surfactant-mediated co-condensation sol-gel process. By utilization of the hydrophobic-hydrophobic interaction between C8-moified pore walls and target molecules, the obtained C8-modified graphene@mSiO2materials exhibit excellent performance in size-selectively and specifically enriching peptides from both standard peptide mixtures and real biological samples.The fourth chapter focuses on the need of peptidomics analysis. Hydrophobic magnetic graphene double-sided mesoporous nanocomposites (mag-graphene@mSiO2) are designed and synthesized by coating a layer of mesoporous silica materials on each side of magnetic graphene. The as-made magnetic graphene double-sided mesoporous silica composites are treated with high-temperature calcination to remove the hydroxyl on the surface. The novel double-sided materials possess high surface area and large pore volume. The highly open pore structure presents uniform pore size and structural stability. The hydrophobic interior pore walls could ensure an efficient adsorption of target molecules through hydrophobic-hydrophobic interaction. At the same time, the magnetic Fe3O4particles on both sides of the materials could simplify the process of enrichment, which plays an important role in the treatment of complex biological samples. The magnetic graphene double-sided nanocomposites are successfully applied to size-selectively and specifically enrichment of peptides in standard peptide mixtures, protein digest solutions, and human urine samples. Finally, the novel material is applied to selective enrichment of endogenous peptides in mouse brain tissue. The enriched endogenous peptides are then analyzed by LC-MS/MS, and409endogenous peptides are detected and identified in result. The consequences demonstrate that the as-made mag-graphene@mSiO2have powerful potential for peptidome research. |
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