Electrochemistry Of Heme-proteins And Analytical Applications

The use of electrochemical techniques to study redox proteins and their active sites has gained increasing attention. Electrochemical methods can be used to extract essential physicochemical data concerning the kinetics and energetics of protein redox reaction and to study mechanisms of electron transfer in metalloproteins. Direct electrochemistry of proteins or enzymes has potential application in fabricating electrochemical biosensors, which combine the speciality of biological recognition element with the advantages of electrochemical methods such as higher sensitivity and operation in situ. Heme-proteins play versatile roles in biological systems. For example, hemoglobin and myoglobin function as a carrier on molecular oxygen. Hemoenzymes like peroxidase and catalase are responsible for the dismutation of hydrogen peroxide.In the thesis, electrodes are modified by bioaffinitic materials to investigate the electrochemical and electrocatalytic properties of hemoproteins or hemoenzymes such as myoglobin, hemoglobin, horseradish peroxidase and catalase, summarized as the following:(1) Four heme proteins, including myoglobin, hemoglobin, horseradish peoxidase and catalase, were immobilized on edge-plane pyrolytic graphite (EPG) electrodes by polysaccharide hydrogel such as methyl cellulose and sodium alginate. The proteins entrapped in the polysaccharide film undergo fast direct transfer-electron reactions, corresponding to Fe^III+ e → Fe^II. The formal potential (E°'), the apparent coverage (G), the electron transfer coefficient (a) and the apparent electron transfer rate constant (k_s) were calculated by integrating cyclic voltammograms or performing nonlinear regression analysis of SWV experimental data. The E°' are linearly dependent on solution pH (redox Bohr effect), indicating the electron transfer of Fe^III/Fe^II redox couple companied with the transfer of proton. Ultraviolet visible (UV-Vis) and reflection absorption infrared (RAIR) spectra suggest that proteins keep their original conformation in the polysaccharide films, and the conformation changes reversibly in a range of pH 3.0-10.0. AFM images indicate a stable and crystal-like structure formed possibly due to the synergistic interaction of hydrogen bonding between N, N- Dimethylformamide (DMF), polysaccharide hydrogel and heme proteins, suggesting a strong interaction between...