title: Peroxide-dependent analyte conversion by the heme prosthetic group, the heme Peptide "microperoxidase-11" and cytochrome C on chitosan capped gold nanoparticles modified electrodes.
abstract: In view of the role ascribed to the peroxidatic activity of degradation products of cytochrome c (cyt c) in the processes of apoptosis, we investigate the catalytic potential of heme and of the cyt c derived heme peptide MP-11 to catalyse the cathodic reduction of hydrogen peroxide and to oxidize aromatic compounds. In order to check whether cyt c has an enzymatic activity in the native state where the protein matrix should suppress the inherent peroxidatic activity of its heme prosthetic group, we applied a biocompatible immobilization matrix and very low concentrations of the co-substrate H2O2. The biocatalysts were entrapped on the surface of a glassy carbon electrode in a biocompatible chitosan layer which contained gold nanoparticles. The electrochemical signal for the peroxide reduction is generated by the redox conversion of the heme group, whilst a reaction product of the substrate oxidation is cathodically reduced in the substrate indication. The catalytic efficiency of microperoxidase-11 is sufficient for sensors indicating HRP substrates, e.g., p-aminophenol, paracetamol and catechol, but also the hydroxylation of aniline and dehalogenation of 4-fluoroaniline. The lower limit of detection for p-aminophenol is comparable to previously published papers with different enzyme systems. The peroxidatic activity of cyt c immobilized in the chitosan layer for catechol was found to be below 1 per mill and for p-aminophenol about 3% as compared with that of heme or MP-11.
authors.affiliation: Fraunhofer Institute for Biomedical Engineering, IBMT, D-14476 Potsdam, Germany. aysu.yarman@yahoo.de.
authors.forename: Aysu
authors.initials: A
authors.lastname: Yarman
authors.affiliation: Fraunhofer Institute for Biomedical Engineering, IBMT, D-14476 Potsdam, Germany. bettina.neumann1@web.de.
authors.forename: Bettina
authors.initials: B
authors.lastname: Neumann
authors.affiliation: Fraunhofer Institute for Biomedical Engineering, IBMT, D-14476 Potsdam, Germany. maria.bosserdt@ibmt.fraunhofer.de.
authors.forename: Maria
authors.initials: M
authors.lastname: Bosserdt
authors.affiliation: Fraunhofer Institute for Biomedical Engineering, IBMT, D-14476 Potsdam, Germany. nenad.gajovic@ibmt.fraunhofer.de.
authors.forename: Nenad
authors.initials: N
authors.lastname: Gajovic-Eichelmann
authors.affiliation: Fraunhofer Institute for Biomedical Engineering, IBMT, D-14476 Potsdam, Germany. fschell@uni-potsdam.de.
authors.forename: Frieder W
authors.initials: FW
authors.lastname: Scheller