Eelectrochemical Research Of Catalase

Catalase consist abroad in animals, plants and microorganisms, and is a kind of important enzyme, have important physiological functions. The major function is that they take part in the metabolic process of active oxygen. Usually, Organism will occur active oxygen bursting out phenomenon with the intimidation of surroundings. It results in the increasing of free radical, oxidation of cell membrane, so as to destroy them. Thereby, catalase have important effect on eliminating the super oxide free radical, H₂O₂and peroxide and further preventing the formation of free radical, in addition, catalase's applications are abroad in real life and productive practice, such as textile industry, grocery industry, paper making industry and environment protection industry and even in circuit ban they are also applied. Among the so many researches, including synthesis, purification, characterization, activity exploration and so on, there are seldom electrochemical investigations applied in catalase. Actually, people adopted electrochemical methods combining the other biological and chemical technology had the important meaning on discovering the essence of life through investigations of organism electron-transfer and related process. Especially in recent years, the researches of modified electrodes theory developed quickly, they supply the more available conditions for electrochemical researches.Under this groundwork, we chose the DNA film existing naturally to modify pyrolytic graphite electrodes(PG) to research a series of electrochemical characters on catalase. In the course of investigation, we discovered that catalase showed a pair of well-defined cyclic voltammetry peaks on DNA modified PG electrodes. The formal potential((E° )for catalase was -0.209V. UV-Vis absorption spectroscopy demonstrated that catalase retained a near native conformation in DNA films. At a dsDNA/PG electrode, reduction and oxidation electron-transfer rate constant values of ks,Red = 13.5 s^-1 and ks,Ox=13.3 s^-1 were obtained. At a ssDNA/PG electrode, the valueswere ksRed = 21.0 s'1 and ks,ox= 33.0 s"1, respectively. The formal potential of Fe(III)/Fe(II) couples in Cat-dsDNA films had a linear relationship within the pH range of 3.81-7.72 with a slope of-58 mV per unit of pH, suggesting that one proton is coupled with single-electron transfer for each heme group of catalase in the electrode reaction. The embedded catalase in DNA films showed the electrocatalytic activity toward hydrogen peroxide.Since the comformation between the single DNA(ssDNA) and double DNA(dsDNA) are different, we guessed to be showed different qualities at these two different electrode. So we did some comparative experiments .The results showed that it's slight faster at ssDNA modified PG than at dsDNA modified PG. Thereafter, we found it showed well-defined cyclic voltammetry peaks at bare coarse edge-plane PG electrode, what's more, the stability of catalase in solution also is good on it. However, other heme protein didn't ever show this phenomenon, so we further investigated the catalase's voltammetrical characters at mEPG(polished into mirror surface electrode), cEPG(polished into coarse surface electrode),]BPG( freshly split basal-plane PG ). After many repeated experiments, the results showed that catalase showed well-defined electrochemical signal at cEPG, but a little responses at the other two. The repeated activity is poor at mEPG ,so in oder to obtain the more information about catalase at cEPG, we investigated a series of electrochemical qualities at cEPG. the electron-transfer rate constant is ks = 2.0229 s"1;and also one proton is coupled with single-electron transfer.