Characterization of electron transfer reactions of microperoxidase assembled at short-chain thiol-monolayers on gold |
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Authors: | L Jiang A Glidle CJ McNeil JM Cooper |
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Institution: | a Bioelectronics Research Centre, Department of Electronics and Electrical Engineering, University of Glasgow, Glasgow G12 8LT, UK b Department of Clinical Biochemistry, University of Newcastle upon Tyne, Newcastle upon Tyne NE2 4HH, UK |
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Abstract: | In this study thiol-monolayers were used in order to modify gold and provide suitable chemical functionalities for the immobilization of the small redox-active haem-containing peptide, microperoxidase (MP-11). Initially, we assembled a variety of thiol-containing species on the gold electrodes and measured a series of electron transfer reactions, each characteristic of the surface-modifier. Using suitable immobilization strategies, we subsequently covalently bound MP-11 to appropriate monolayers and found two characteristic electrochemical responses (i.e. using MP-11 bound to mercaptopropionic acid, redox peaks were seen at E0′ = −315 mV and at +179 mV versus Ag|AgCl, with the former being attributed to the haem and the latter with the thiol monolayer). Exposure of the peptide-thiol surface to UV irradiation resulted in cleavage of the Au---S bond, leading to a decrease in the magnitude of both responses. Our work is supported by corroborative evidence showing the immobilization of the peptide, obtained using both X-ray photoelectron and reflectance Fourier transform infra-red spectroscopies. We hypothesize that differences in the ionic charges on the protein backbone account for the shift in E0′ for MP-11, as observed in our system, when compared to that found for MP-11 immobilized by different strategies. |
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Keywords: | electron transfer reaction microperoxidase thiol monolayer XPS FT-IR spectroscopy |
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