Study Of The Electrochemical Behaviors Of Biological Enzyme And Its Catalytic Application

With the understanding of biological enzyme and studying in depth, the advantages of biological enzyme in catalysis have being discovered and applied widely. Combination of electrochemical methods and enzymes, need less than normal organic reactions and are economical, efficient, in line with the requirements of today's green chemistry.Chloride peroxidase (CPO) is excreted by the filamentous fungus Caldariomyces fumago. It was reported that CPO has been widely used for catalytic reactions such as dehydrogenase catalyzed oxidation, halogenation, epoxidation. CPO has broad application prospects in some area, such as organic synthesis and the production of drug intermediates. However, the immobilization of CPO on the electrode is the premise of catalysis with electrochemical methods.In this paper, the mobilization of Myoglobin (Mb) and Hemoglobin (Hb) have been tried with Poly-L-lysine (PLL) on the Pyrolytic graphite (PG) electrode by dropping layer by layer. First, the film of N-(3-dimethylaminopropyl)-N-ethylcarbodi- imide hydrochloride (EDC) was grown on electrode surface, which have been pretreated by cyclic scanned from 1.5 to 1.7 V for one cycle. Then PLL was dropped onto the EDC/PG electrode. Finally, the mixture of Mb and Hb solution and EDC was dropped onto the PLL-EDC/PG. The results of cyclic voltammetry of CPO-PLL/PG electrode showed that direct electron transfers of Mb or Hb was observed. The CPO-PLL/PG electrode has a good stability and a good catalytic effect for the oxygen reduction reaction.Then, the same modification has been applied to immobilization of CPO. The results of cyclic voltammetry showed that a pair of well-defined reduction and oxidation peaks was observed at the CPO-PLL/PG electrode in the range of 0.15 to -0.8 V vs SCE. The cyclic voltammograms of CPO-PLL/PG electrode in deferent pH PBS were also investigated. The cyclic voltammograms measured in various pH PBS showed that the formal potential (E0') shifted negatively with the solution increased in the range from 3 to 7. The liner relationship of the E0'versus pH demonstrated that proton transfer is coupled to the redox reaction of CPO.The reduction reaction of toluene catalyzed with CPO-PLL/PG electrode at constant-potential was investigated. The products were analyzed by HPLC and the catalysis efficiency of CPO-PLL/PG electrode has been estimated in the reduction reaction of toluene.