title: Photoelectron generation by photosystem II core complexes tethered to gold surfaces.
abstract: By using a nondestructive, ultrasensitive, fluorescence kinetic technique, we measure in situ the photochemical energy conversion efficiency and electron transfer kinetics on the acceptor side of histidine-tagged photosystem II core complexes tethered to gold surfaces. Atomic force microscopy images coupled with Rutherford backscattering spectroscopy measurements further allow us to assess the quality, number of layers, and surface density of the reaction center films. Based on these measurements, we calculate that the theoretical photoelectronic current density available for an ideal monolayer of core complexes is 43 microA cm(-2) at a photon flux density of 2000 micromol quanta m(-2) s(-1) between 365 and 750 nm. While this current density is approximately two orders of magnitude lower than the best organic photovoltaic cells (for an equivalent area), it provides an indication for future improvement strategies. The efficiency could be improved by increasing the optical cross section, by tuning the electron transfer physics between the core complexes and the metal surface, and by developing a multilayer structure, thereby making biomimetic photoelectron devices for hydrogen generation and chemical sensing more viable.
authors.affiliation: Department of Chemistry and Chemical Biology, Rutgers, The State University of New Jersey, Piscataway, NJ 08854, USA. mvittadello@mec.cuny.edu
authors.forename: Michele
authors.initials: M
authors.lastname: Vittadello
authors.forename: Maxim Y
authors.initials: MY
authors.lastname: Gorbunov
authors.forename: Daniel T
authors.initials: DT
authors.lastname: Mastrogiovanni
authors.forename: Leszek S
authors.initials: LS
authors.lastname: Wielunski
authors.forename: Eric L
authors.initials: EL
authors.lastname: Garfunkel
authors.forename: Fernando
authors.initials: F
authors.lastname: Guerrero
authors.forename: Diana
authors.initials: D
authors.lastname: Kirilovsky
authors.forename: Miwa
authors.initials: M
authors.lastname: Sugiura
authors.forename: A William
authors.initials: AW
authors.lastname: Rutherford
authors.forename: Ahmad
authors.initials: A
authors.lastname: Safari
authors.forename: Paul G
authors.initials: PG
authors.lastname: Falkowski
mesh_terms: D000458:Cyanobacteria / Q000201:enzymology; D004579:Electron Transport; D004800:Enzymes, Immobilized / Q000737:chemistry / Q000378:metabolism; D006046:Gold / Q000737:chemistry*; D007700:Kinetics; D055668:Photochemical Processes; D045332:Photosystem II Protein Complex / Q000737:chemistry* / Q000378:metabolism; D013050:Spectrometry, Fluorescence; D013499:Surface Properties
chemical_list: D004800:Enzymes, Immobilized; D045332:Photosystem II Protein Complex; D006046:Gold