title: Photosynthetic reaction centers/ITO hybrid nanostructure.
abstract: Photosynthetic reaction center proteins purified from Rhodobacter sphaeroides purple bacterium were deposited on the surface of indium tin oxide (ITO), a transparent conductive oxide, and the photochemical/-physical properties of the composite were investigated. The kinetics of the light induced absorption change indicated that the RC was active in the composite and there was an interaction between the protein cofactors and the ITO. The electrochromic response of the bacteriopheophytine absorption at 771 nm showed an increased electric field perturbation around this chromophore on the surface of ITO compared to the one measured in solution. This absorption change is associated with the charge-compensating relaxation events inside the protein. Similar life time, but smaller magnitude of this absorption change was measured on the surface of borosilicate glass. The light induced change in the conductivity of the composite as a function of the concentration showed the typical sigmoid saturation characteristics unlike if the photochemically inactive chlorophyll was layered on the ITO. In this later case the light induced change in the conductivity was oppositely proportional to the chlorophyll concentration due to the thermal dissipation of the excitation energy. The sensitivity of the measurement is very high; few picomole RC can change the light induced resistance of the composite.
authors.affiliation: Department of Medical Physics and Informatics, University of Szeged, Szeged, Hungary.
authors.forename: Tibor
authors.initials: T
authors.lastname: Szabó
authors.affiliation: Department of Physical Chemistry and Materials Science, University of Szeged, Szeged, Hungary.
authors.forename: Gábor
authors.initials: G
authors.lastname: Bencsik
authors.affiliation: Department of Medical Physics and Informatics, University of Szeged, Szeged, Hungary.
authors.forename: Melinda
authors.initials: M
authors.lastname: Magyar
authors.affiliation: Department of Physical Chemistry and Materials Science, University of Szeged, Szeged, Hungary.
authors.forename: Csaba
authors.initials: C
authors.lastname: Visy
authors.affiliation: Department of Technical Informatics, University of Szeged, Szeged, Hungary.
authors.forename: Zoltán
authors.initials: Z
authors.lastname: Gingl
authors.affiliation: Institute of Biophysics, Hungarian Academy of Sciences, Biological Research Center, Szeged, Hungary.
authors.forename: Krisztina
authors.initials: K
authors.lastname: Nagy
authors.affiliation: Institute of Biophysics, Hungarian Academy of Sciences, Biological Research Center, Szeged, Hungary.
authors.forename: György
authors.initials: G
authors.lastname: Váró
authors.affiliation: Department of Medical Physics and Informatics, University of Szeged, Szeged, Hungary.
authors.forename: Kata
authors.initials: K
authors.lastname: Hajdu
authors.affiliation: Department of Medical Physics and Informatics, University of Szeged, Szeged, Hungary.
authors.forename: Gábor
authors.initials: G
authors.lastname: Kozák
authors.affiliation: Department of Medical Physics and Informatics, University of Szeged, Szeged, Hungary. Electronic address: lnagy@sol.cc.u-szeged.hu.
authors.forename: László
authors.initials: L
authors.lastname: Nagy
mesh_terms: D004553:Electric Conductivity; D007700:Kinetics; D008027:Light; D018625:Microscopy, Atomic Force; D049329:Nanostructures / Q000737:chemistry*; D045322:Photosynthetic Reaction Center Complex Proteins / Q000737:chemistry / Q000378:metabolism*; D012242:Rhodobacter sphaeroides / Q000378:metabolism*; D017971:Tin Compounds / Q000737:chemistry*
chemical_list: D045322:Photosynthetic Reaction Center Complex Proteins; D017971:Tin Compounds; C109984:indium tin oxide