Direct Electrochemistry And Its Application For Catalysis Reactions Of Chloroperoxidase At GC Modified With SWNTs

The lysine is the basic element to compose the organism which has the function of the amino group as well as the carboxyl group. There are many free amino existing in the poly-L-lysine which has great affinity to the protein, as well as high thermostability, chemical stability and mechanics. Therefore the poly-L-lysine is an ideal support to immobilize the enzyme because the adsorption between the cell or molecular and the surface of the electrode can accelerate the transfer of the electron. In this work, the PLL is chosen as the support to immobilize the enzyme.We first used the Hemoglobin (Hb) which has the similar molecular weight and property to the CPO as the model, in order to explore the way of immobilization which was then applied to the CPO. Poly-L-lysine (PLL) was electropolymerized onto the surface of glassy carbon (GC) electrode. 1-[(3-dimethylamino)propyl]-3-ethyl- carbodiimide hydrochloride (EDC) was used a cross-linking agent to immobilized chloroperoxidase (CPO) onto the PLL/GC electrode. A pair of well-defined redox peaks was observed at CPO-PLL/GC electrode clearly suggested that PLL can promote the direct electron transfer between the CPO and the GC electrode. The cyclic voltammetric results also showed that the electron transfer at CPO-PLL/GC is a surface adsorption- controlled quasi-reversible process, which is accompanied with proton transfer. The CPO-PLL/GC electrode exhibited a good electrochemical stability and excellently electrocatalytic activity for electrochemical reduction of O2.The CPO-PLL-CPO-PLL/GC electrode was prepared based on the similar preparation method of CPO-PLL/GC electrode. The electrochemical behaviors of immobilized CPO on electrode were investigated by cyclic voltammetry (CV). The CV results obtained showed that CPO was successfully immobilized on the PLL/GC electrode and a fast direct electron transfer between CPO and electrode has been achieved. And the results of cyclic voltammetry with different scan rates revealed that the direct electron transfer is a reaction controlled by the surface adsorption process. The CPO-PLL-CPO-PLL/GC modified electrode showed a good catalytic activity for electrocatalytical reduction of O2. To investigate the pH dependence, cyclic voltammetry was performed at different pH. An increase in pH of buffer solutions led to a negative shift in both reduction and oxidation peak potentials, linear relationship of formal potential vs. pH with a slope of 39 mV / pH.In this study, modified electrode of CPO-PLL/GC have been applied to catalyze the chlorination of monochlorodimedone (MCD, have UV adsorption at 278 nm) to didochlorodimedone (DCD, no UV adsorption at 278 nm) using a unique electrochemical system which used UV spectrum adsorption to observe the reaction. The results of UV showed that MCD has been catalyzed to DCD with CPO-PLL/GC modified electrode. The catalyzed mechanism of CPO was discussed.