title: Single-molecule spectroscopy unmasks the lowest exciton state of the B850 assembly in LH2 from Rps. acidophila.
abstract: We have recorded fluorescence-excitation and emission spectra from single LH2 complexes from Rhodopseudomonas (Rps.) acidophila. Both types of spectra show strong temporal spectral fluctuations that can be visualized as spectral diffusion plots. Comparison of the excitation and emission spectra reveals that for most of the complexes the lowest exciton transition is not observable in the excitation spectra due to the cutoff of the detection filter characteristics. However, from the spectral diffusion plots we have the full spectral and temporal information at hand and can select those complexes for which the excitation spectra are complete. Correlating the red most spectral feature of the excitation spectrum with the blue most spectral feature of the emission spectrum allows an unambiguous assignment of the lowest exciton state. Hence, application of fluorescence-excitation and emission spectroscopy on the same individual LH2 complex allows us to decipher spectral subtleties that are usually hidden in traditional ensemble spectroscopy.
authors.affiliation: Experimental Physics IV and Bayreuth Institute for Macromolecular Research (BIMF), University of Bayreuth, Bayreuth, Germany.
authors.forename: Ralf
authors.initials: R
authors.lastname: Kunz
authors.affiliation: Institute of Physics, University of Tartu, Tartu, Estonia.
authors.forename: Kõu
authors.initials: K
authors.lastname: Timpmann
authors.affiliation: Institute of Molecular, Cell and Systems Biology, College of Medical Veterinary and Life Sciences, Biomedical Research Building, University of Glasgow, Glasgow, Scotland, United Kingdom.
authors.forename: June
authors.initials: J
authors.lastname: Southall
authors.affiliation: Institute of Molecular, Cell and Systems Biology, College of Medical Veterinary and Life Sciences, Biomedical Research Building, University of Glasgow, Glasgow, Scotland, United Kingdom.
authors.forename: Richard J
authors.initials: RJ
authors.lastname: Cogdell
authors.affiliation: Institute of Physics, University of Tartu, Tartu, Estonia; Institute of Molecular and Cell Biology, University of Tartu, Tartu, Estonia.
authors.forename: Arvi
authors.initials: A
authors.lastname: Freiberg
authors.affiliation: Experimental Physics IV and Bayreuth Institute for Macromolecular Research (BIMF), University of Bayreuth, Bayreuth, Germany. Electronic address: juergen.koehler@uni-bayreuth.de.
authors.forename: Jürgen
authors.initials: J
authors.lastname: Köhler
mesh_terms: D004058:Diffusion; D045342:Light-Harvesting Protein Complexes / Q000737:chemistry* / Q000378:metabolism; D012241:Rhodopseudomonas / Q000201:enzymology*; D013050:Spectrometry, Fluorescence
chemical_list: D045342:Light-Harvesting Protein Complexes