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Attachment and Application and Electrocatalytic Behavior of Catalase Biosensor and Electrochemical I

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Tutor: TianYanNi
School: Shanxi University
Course: Inorganic Chemistry
Keywords: Catalase biosensors,Centrin,Eu3+,Cyclic voltammetry,Electrochemical impedance sp
CLC: Q504
Type: Master's thesis
Year:  2009
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Catalase biosensors which utilize immobilized oxidase for the conversion of the target analytes into electrochemically detectable products are one of the most widely used detection methods and have become an area of wide ranging research activity.Recent advances in biocompatible nano technology make it possible to develop new biosensors.In one part of this paper,a highly hydrophilic,non-toxic and conductive colloidal gold nanoparticles(GNP) and multi-walled carbon nanotubes (MWCNT) on pyrolytic graphite electrode has been demonstrated.The direct electron transfer of catalase(CAT) was achieved based on the immobilization of MWCNT/CAT-GNP on a pyrolytic graphite electrode by a Nafion film. The immobilized catalase displayed a pair of well-defined and nearly reversible redox peaks in 0.1 M phosphate buffer solution(PBS)(pH 6.98). The dependence of E0′on solution pH indicated that the direct electron transfer reaction of catalase was a single-electron-transfer coupled with single-proton-transfer reaction process.The immobilized catalase maintained its biological activity,showing a surface controlled electrode process with the apparent heterogeneous electron transfer rate constant(ks) of 3.98 s-1 when charge-transfer coefficient was 0.5,and displays electrocatalytic activity in the electrocatalytic reduction of hydrogen peroxide.So the resulting modified electrode can be used as a biosensor for detecting hydrogen peroxide.Centrin(caltractin) is a member of the calmodulin(CAM) superfamily of EF-hand calcium-binding proteins.It is required for proper cell division,and plays an important role in contraction of centrin-based fiber systems in eukaryotic cells as well.In the other hand of this paper,the Eu3+,is reported to study Ciliate Euplotes octocarinatus centrin for the first time.The binding process of Eu3+ with P23(one segment of Centrin),has been investigated by cyclic voltammetry,electrochemical impedance spectroscopy and pulse voltammetry in pH 7.4 10 mM N-2-hydroxy-ethylpiperazine-N-2-ethane-sulfonic acid buffer solution(Hepes) at a pyrolytic graphite electrode.The formal potential(E0′) of Eu3+ shifted obviously to the negative direction from -0.610 V to -0.839 V(versus saturated calomel electrode) when P23 was added into the Eu3+ solution.The values of the electrochemical parameters, the charge-transfer coefficient(α) and the electrochemical reaction standard rate constant(ks),were obtained in the absence and presence of P23.The kinetic affinity constant,(1.86±0.51)×104 M-1 was calculated by pulse voltammetry.The present working mainly investigated the coordination between Eu3+ and Centrin(Cen) by electrochemistry spectra,on the one hand, can help to clarify the many properties of lower eukaryotes,such as cell division,mobile cell;on the other hand,shed more light on chemical bases of rare earhe effect using centrin as possible binding target model.
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