title: Direct electron transfer reactions between human ceruloplasmin and electrodes.
abstract: In an effort to find conditions favouring bioelectrocatalytic reduction of oxygen by surface-immobilised human ceruloplasmin (Cp), direct electron transfer (DET) reactions between Cp and an extended range of surfaces were considered. Exploiting advances in surface nanotechnology, bare and carbon-nanotube-modified spectrographic graphite electrodes as well as bare, thiol- and gold-nanoparticle-modified gold electrodes were considered, and ellipsometry provided clues as to the amount and form of adsorbed Cp. DET was studied under different conditions by cyclic voltammetry and chronoamperometry. Two Faradaic processes with midpoint potentials of about 400 mV and 700 mV vs. NHE, corresponding to the redox transformation of copper sites of Cp, were clearly observed. In spite of the significant amount of Cp adsorbed on the electrode surfaces, as well as the quite fast DET reactions between the redox enzyme and electrodes, bioelectrocatalytic reduction of oxygen by immobilised Cp was never registered. The bioelectrocatalytic inertness of this complex multi-functional redox enzyme interacting with a variety of surfaces might be associated with a very complex mechanism of intramolecular electron transfer involving a kinetic trapping behaviour.
authors.affiliation: Malmö University, Södra Förstadsgatan 101, 20506 Malmö, Sweden.
authors.forename: Karolina
authors.initials: K
authors.lastname: Haberska
authors.forename: Cristina
authors.initials: C
authors.lastname: Vaz-Domínguez
authors.forename: Antonio L
authors.initials: AL
authors.lastname: De Lacey
authors.forename: Marius
authors.initials: M
authors.lastname: Dagys
authors.forename: Curt T
authors.initials: CT
authors.lastname: Reimann
authors.forename: Sergey
authors.initials: S
authors.lastname: Shleev
mesh_terms: D000327:Adsorption; D055162:Biocatalysis; D002570:Ceruloplasmin / Q000737:chemistry* / Q000378:metabolism; D004563:Electrochemistry; D004566:Electrodes; D004579:Electron Transport; D004800:Enzymes, Immobilized / Q000737:chemistry / Q000378:metabolism; D006046:Gold / Q000737:chemistry; D006108:Graphite / Q000737:chemistry; D006801:Humans; D007700:Kinetics; D053768:Metal Nanoparticles / Q000737:chemistry; D008958:Models, Molecular; D037742:Nanotubes, Carbon / Q000737:chemistry; D010100:Oxygen / Q000737:chemistry / Q000378:metabolism; D011487:Protein Conformation; D013438:Sulfhydryl Compounds / Q000737:chemistry; D013499:Surface Properties; D013816:Thermodynamics
chemical_list: D004800:Enzymes, Immobilized; D037742:Nanotubes, Carbon; D013438:Sulfhydryl Compounds; D006046:Gold; D006108:Graphite; D002570:Ceruloplasmin; D010100:Oxygen