title: Photocurrent of a single photosynthetic protein.
abstract: Photosynthesis is used by plants, algae and bacteria to convert solar energy into stable chemical energy. The initial stages of this process--where light is absorbed and energy and electrons are transferred--are mediated by reaction centres composed of chlorophyll and carotenoid complexes. It has been previously shown that single small molecules can be used as functional components in electric and optoelectronic circuits, but it has proved difficult to control and probe individual molecules for photovoltaic and photoelectrochemical applications. Here, we show that the photocurrent generated by a single photosynthetic protein-photosystem I-can be measured using a scanning near-field optical microscope set-up. One side of the protein is anchored to a gold surface that acts as an electrode, and the other is contacted by a gold-covered glass tip. The tip functions as both counter electrode and light source. A photocurrent of ∼10 pA is recorded from the covalently bound single-protein junctions, which is in agreement with the internal electron transfer times of photosystem I.
authors.affiliation: Physik-Department E20, Technische Universität München, James-Franck Strasse, D-85748                 Garching, Germany.
authors.forename: Daniel
authors.initials: D
authors.lastname: Gerster
authors.forename: Joachim
authors.initials: J
authors.lastname: Reichert
authors.forename: Hai
authors.initials: H
authors.lastname: Bi
authors.forename: Johannes V
authors.initials: JV
authors.lastname: Barth
authors.forename: Simone M
authors.initials: SM
authors.lastname: Kaniber
authors.forename: Alexander W
authors.initials: AW
authors.lastname: Holleitner
authors.forename: Iris
authors.initials: I
authors.lastname: Visoly-Fisher
authors.forename: Shlomi
authors.initials: S
authors.lastname: Sergani
authors.forename: Itai
authors.initials: I
authors.lastname: Carmeli
mesh_terms: D002338:Carotenoids / Q000737:chemistry*; D002734:Chlorophyll / Q000737:chemistry*; D004579:Electron Transport; D008027:Light; D045331:Photosystem I Protein Complex / Q000737:chemistry*
chemical_list: D045331:Photosystem I Protein Complex; D002734:Chlorophyll; D002338:Carotenoids