Functionalized Graphene Oxide:Preparation And Application For Proteomics Research

Graphene oxide, as an important precursor for preparing graphene, apart from the special layered structure with a large theoretical specific surface area, bears abundant oxide containing groups, such as hydroxyl, epoxy and carboxylic groups. The presence of functional groups not only improves the hydrophilicity of graphene oxide, but also offers reaction sites for preparing functionalfzed graphene oxide. In this dissertation, we focus on prepare novel functionalized graphene oxide materials, and study the application of materials in sample pretreatment in proteomics.The immobilized enzyme reactor (IMER) based on magnetic graphene oxide was prepared and used for microwave-assisted protein digestion. The IMER possesses excellent hydrophilicity, and the binding capacity of trypsin reaches to0.275mg/mg. By such an IMER, standard proteins could be efficiently digested within15s, with comparable to those obtained by conventional in-solution digestion (12h). By such IMER,456different proteins are identified from2μg rat-liver.The IMER based on dendrimer grafted graphene oxide was prepared and used for on-plates protein digestion. The IMER possesses excellent hydrophilicity, and the binding capacity of trypsin reaches to0.649mg/mg. By such an IMER, standard proteins could be efficiently digested within15min, with sequence coverages comparable to those obtained by conventional in-solution digestion. Rapid digestion and accurate identification for trace sample (150fmol Myo) is achieved by the IMER, because on-plates digestion reduces samples losses. By such IMER,125different proteins are identified from2μg human plasma.L-Cysteine functionalized graphene oxide nanocomposites (GO/PEI/Au/L-Cys) were prepared and used as a novel ZIC-HILIC material for selective enrichment of N-linked glycopeptides. GO/PEI/Au/L-Cys displays the advantages of excellent hydrophilicity, large surface area and high immobilized amount of L-Cysteine. GO/PEI/Au/L-Cys shows remarkable selectivity for N-linked glycopeptides even in the presence of100fold non-glycopeptides. By such nanocomposites,87different glycoproteins are identified from5μg tryptic human serum, which is better than the commercial ZIC-HILIC material (76).4-mercaptophenylboronic acid functionalized graphene oxide nanocomposites (GO/PEI/Au/4-MPB) were prepared and used as novel boronic affinity material for selective enrichment of N-linked glycopeptides. GO/PEI/Au/4-MPB displays the advantages of excellent hydrophilicity, large surface area and high immobilized amount of4-mercaptophenylboronic acid. GO/PEI/Au/4-MPB shows remarkable selectivity for N-linked glycopeptides even in the presence of100fold non-glycopeptides, which is better than commercial boronic acid resin.PEG functionalized magnetic graphene oxide nanocomposites (GO/Fe3O4/PEI/Au/PEG) were prepared and used as novel HILIC material for selective enrichment of N-linked glycopeptides. The nanocomposites shows remarkable selectivity for N-linked glycopeptides even in the presence of100fold non-glycopeptides, which is due to its excellent hydrophilicity. By such nanocomposites,127different glycoproteins are identified from20μg tryptic human plasma, which is better than click maltose.Silver nanoparticles were attached on magnetic graphene oxide nanocomposites using NaBH4as reducing reagent (GO/Fe3O4/PEI/Ag). The selective enrichment of N-linked glycopeptides was obtained by utilizing the multivalent interaction between glycopeptides and GO/Fe3O4/PEI/Ag nanocomposites. GO/Fe3O4/PEI/Ag shows remarkable selectivity for N-linked glycopeptides even in the presence of100fold non-glycopeptides, which is due to excellent hydrophilicity of the nanocomposites. By such nanocomposites,91different glycoproteins are identified from20μg tryptic human plasma.