Electrochemical Properties Of Proteins At Apatite And Nano-Alumina Assembly System

Direct electron transfer between redox proteins and electrodes is of practical and theoretical interest for the realization of the biological energy transfer and substance metabolism. The direct contact of protein with electrode surfaces can lead to a significant change of the protein structure and /or function, result in denaturation and electron transfer barrier of the proteins on the electrode surface. Apatite, alumina (AAO) templates and colloid gold nanopartical provide a microenvironment similar to that of the redox protein in native systems and give the protein molecules more freedom in orientation, thus reduce the insulting property of the protein shell for the direct electron transfer and facilitate the electron transfer. In order to understand fully the essential of reversible electron transfer of proteins in organism, in this thesis, the following topics related to the apatite, AAO templates and colloid gold nanopartical in proteins immobilization, direct electrochemistry and electrocatalysis are studied. 1 Effect of apatite on the direct electrochemistry of Cyt c In this paper, a novel favorite electron transfer promoter of apatite was developed and the direct electrochemistry of Cyt c on the hydroxyapatite, fluorapatite and chlorapatite modified glassy carbon electrodes were investigated. CVs of Cyt c on the apatite modified glassy carbon electrodes showed a pair of well-defined and nearly reversible peaks at about 0.074 V (vs.Ag /AgCl) in pH 7.0 PBS buffers, being the characteristic peaks of the Cyt c heme Fe(Ⅲ) / Fe(Ⅱ)redox couples. It was a diffusion-controlled redox process at scan rates from 40 to 400 mV s-1. The P sites of negative charges on apatite attached to the positive charges of the lysine residues, which made the heme sites of Cyt c take effective orientation and allowed the direct electron transfer to take place. The electron transfer rate constants ko of Cyt c at fluorapatite, hydroxyapatite and chlorapatite modified glassy electrodes were 3.0×10-6, 3.9×10-6 and 4.2×10-6 cm·s-1 according to the Nicholson's equation, respectively. This difference may be resulted from the different electrostatic interaction between apatite and Cyt c. 2 Direct electrochemistry and electrocatalysis of Cyt c promoted by nano-AAO templates AAO/dithiodipyridine(PySSPy)/Au electrodes were prepared by modified PySSPy on alumina (AAO) templates coated gold electrodes. A pair of redox peaks was observed at the modified electrodes with a formal potential of 65 mV in pH = 6.8, 200 μmol/L Cyt c + 5 mmol/L PBS + 0.1 mol/L NaClO4. The response showed a diffusion-controlled redox process at scan rates from 20 to 500 mV s-1. The separation of peak potentials was 70 mV, which decreased 21 mV compared with that in the absence of AAO templates. This attributed to the more ordered assembly of PySSPy in the presence of AAO templates. The effects of pore diameter of AAO templates and pH on the electrochemical behavior of Cyt c were investigated. The apparent diffusion coefficient Dapp of Cyt c in nanoporous AAO templates was 3.4×10-7 cm2 s-1 measured by chronoamperometry. The immobilized Cyt c displayed a couple of redox peaks with a formal potential of 49 mV in 5 mmol/L PBS (pH = 6.8), a surface controlled electron transfer process at the scan rates from 50 to 500 mV s-1, and negative shifted about 16 mV compared to that of the Cyt c in solution. It may result from the changed heme environment upon binding to the electrodes surface. Cyt c/AAO/PySSPy/Au electrodes displayed also an excellent electrocatalytic response to the reduction of hydrogen peroxide without the aid of electron mediator. The linear relation for H2O2 determination was from 2 to 10 mmol / L. 3 Direct electrochemistry and its electrocatalytic activity of Cyt c immobilized on nano-AAO-colloidal gold assembly system The direct electron transfer between immobilized Cyt c and AAO template -colloidal gold nano-structured system modified gold electrode was studied. The Cyt c immobilized on the colloidal gold na...