Electrochemical And Electrocatalytic Properties Of Microperoxidase-11

Microperoxidase-ll (MP-11) is the product of proteolytic digestion of cytochrome C. It consists of an iron porphyrin and an a -helical undecapeptide. MP-11 can undergo the direct and effective electron transfer between its electroactive center and the electrode surface because its short peptide and large exposure extent of the electroactive center. It can catalyze the reduction of O2, H2O2 and peroxides. Thus, it possesses the potential application prospect in biofuel cell and H2O2 sensor etc. In addition, because it is a small biomacromolecule, it can be used as the model of biomacromolecules to study its electrochemical and electrocatalytic properties as well as interaction of MP-11 and other substances in order to lay the foundation for the study of other biomacromolecules.In this thesis, the preparation methods of MP-11 modified electrode and the electrocatalytic activities of the MP-11 modified electrodes obtained for the reduction of O2 and H2O2 as well as the interaction between MP-11 and La3+ were studied. The main results obtained are as follows:1. Using poly-lysine (Ply) adsorbed on roughed silver electrode, it is easy to immobilize MP-11 with the electrostatic interaction and to prepare the MP-11/Ply/Ag modified electrode. The preparation method of the modified electrode is simple. In addition, the modified electrode obtained showed the high and stable electrocatalytical activity for 62 reduction. It is also found that when the sixth coordination of heme in MP-11 is replaced with other coordination species with stronger coordination ability, such as imidazole, its formal redox potential shifts to the negative direction and the electrocatalytic activity for the reduction of oxygen is reduced.2.MP-11 was absorbed on the active carbon with adsorption method obtaining the MP-ll/C modified electrode. It is found that the preparation method of the modified electrode is simple. The adsorbed MP-11 is not denatured. The MP-11 loading is high. The modified electrode obtained has good stability. The MP-ll/C electrode obtained has the high electrocatalytic activity for the reduction of 62 and HjOa. The result showed that MP-ll/C possessed good electrocatalytic activity for the reduction of O2 and H2O2. It provides a reliable method for the immobolization of enzymes and a promising catalyst for the reduction of O2 in the biofuel cells.3.The results of the electrochemical measurements and UV-vis adsorption spectroscopy indicated that MP-11 could interact with La3+. The interaction between MP-11 and La3+ is a slow process. As the results of the interaction, the electrochemical behavior ischanged and the electrocatalytic ability for H2O2 reduction is increased.