Graphene Oxide And Ionic Liquids In The Seperation And Determination Of Proteins

As a kind of important biomacromolecules, protein plays crucial role in various life activities. Rapid and efficient separation and accurate determination of proteins from complex matrices is of great importance for proteomics. In the present work, graphene oxide and ionic liquid are used for the protein assay and new methods are developed for the separation/purificantion and quantification of proteins, demonstrates novel applications of graphene oxide and ionic liquid in life sciences.In chapter1, a review is given to the separation/purification and quantification of proteins, the properties of graphene oxide and ionic liquid as well as their applications in anlytical biochemistry.In chapter2, a noval GO/SiO2composite is prepared and employed as adsorbent for the selective separation/purification of hemoglobin (Hb) from human whole blood. Graphene oxide (GO) nanosheets are immobilized onto SiO2particles through electrostatic interaction by surface assembly. The obtained composites are characterized by means of SEM, FTIR and UV/Vis spectroscopy. An assembling ratio of2.3%(w/w, GO/SiO2) is achieved. The GO/SiO2composites are subsequently used as the adsorbent for the adsorption/isolation of proteins. Under pH7, an adsorption of85%for1.0mL70mg L-1Hb is achieved by using3.0mg of GO/SiO2composites as sorbent. The adsorption of Hb onto GO/SiO2composites fits the Langmuir adsorption model, corresponding to a theoretical adsorption capacity of50.5mg g-1. The retained Hb could be readily recovered by using a Tris-HCl buffer of pH8.9, giving a recovery of80%. Circular dichroism and specific activity investigations indicate the adsorption/desorption procedures pose no effect on the conformation and activity of Hb, showing favorable biocompatibility of the GO/SiO2composites. The composites are thus used for the selective isolation of Hb from human whole blood. The results of sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) indicate that high purity of hemoglobin is obtained.In chapter3, a highly fluorescent hydrophilic ionic liquid1,3-butylimidazolium chloride (BBimCl) is synthesized and employed as a new fluorescent probe for the quantification of Hb. The high symmetrical plane conjugating structure of BBimCl makes it highly fluorescent. The quantum yield for the aqueous BBimCl is derived to be0.523, with the maximum of λem at388nm and λex at315nm. The fluorescence of BBimCl could be significantly quenched by the addition of Hb, resulting from the coordinating interaction between the iron atom in the heme group of Hb and the cationic imidazolium moiety of BBimCl. This highly fluorescent feature of BBimCl and its specific interaction with Hb makes it to be a promising fluorescence probe for the sensitive quantification of Hb. At the condition of0.01mol L"1BBimCl and pH7, Hb in the range of3×10-7-5×10-6mol L-1could be accurately determined. The detection limit is dedued to be7.3×10-8mol L-1, along with a relative standard deviation (RSD) of0.83%at1×10-6mol L-1(n=9).