title: Surface-tuned electron transfer and electrocatalysis of hexameric tyrosine-coordinated heme protein.
abstract: Molecular modeling, electrochemical methods, and quartz crystal microbalance were used to characterize immobilized hexameric tyrosine-coordinated heme protein (HTHP) on bare carbon or on gold electrodes modified with positively and negatively charged self-assembled monolayers (SAMs), respectively. HTHP binds to the positively charged surface but no direct electron transfer (DET) is found due to the long distance of the active sites from the electrode surfaces. At carboxyl-terminated surfaces, the neutrally charged bottom of HTHP can bind to the SAM. For this "disc" orientation all six hemes are close to the electrode and their direct electron transfer should be efficient. HTHP on all negatively charged SAMs showed a quasi-reversible redox behavior with rate constant ks values between 0.93 and 2.86 s(-1) and apparent formal potentials ${E{{0{^{\prime }}\hfill \atop {\rm app}\hfill}}}$ between -131.1 and -249.1 mV. On the MUA/MU-modified electrode, the maximum surface concentration corresponds to a complete monolayer of the hexameric HTHP in the disc orientation. HTHP electrostatically immobilized on negatively charged SAMs shows electrocatalysis of peroxide reduction and enzymatic oxidation of NADH.
authors.affiliation: Institute of Biochemistry and Biology, Potsdam University, Karl-Liebknecht-Strasse 24-25, 14476 Potsdam (Germany), Fax: (+49) 331 977-5050.
authors.forename: Lei
authors.initials: L
authors.lastname: Peng
authors.forename: Tillmann
authors.initials: T
authors.lastname: Utesch
authors.forename: Aysu
authors.initials: A
authors.lastname: Yarman
authors.forename: Jae-Hun
authors.initials: JH
authors.lastname: Jeoung
authors.forename: Silke
authors.initials: S
authors.lastname: Steinborn
authors.forename: Holger
authors.initials: H
authors.lastname: Dobbek
authors.forename: Maria Andrea
authors.initials: MA
authors.lastname: Mroginski
authors.forename: Johannes
authors.initials: J
authors.lastname: Tanne
authors.forename: Ulla
authors.initials: U
authors.lastname: Wollenberger
authors.forename: Frieder W
authors.initials: FW
authors.lastname: Scheller
mesh_terms: D002384:Catalysis; D004566:Electrodes; D004579:Electron Transport; D004800:Enzymes, Immobilized / Q000737:chemistry*; D006046:Gold / Q000737:chemistry; D006420:Hemeproteins / Q000737:chemistry*; D007700:Kinetics; D008958:Models, Molecular; D014443:Tyrosine / Q000737:chemistry*
chemical_list: D004800:Enzymes, Immobilized; D006420:Hemeproteins; D014443:Tyrosine; D006046:Gold
keywords: electrochemistry; electron transfer; heme proteins; molecular modeling; monolayers