title: Fluorescence spectral fluctuations of single LH2 complexes from Rhodopseudomonas acidophila strain 10050.
abstract: We have investigated the energy landscape of the bacterial photosynthetic peripheral light-harvesting complex LH2 of purple bacterium Rhodopseudomonas acidophila by monitoring sequences of fluorescence spectra of single LH2 assemblies, at room temperature, with different excitation intensities as well as at elevated temperatures, utilizing a confocal microscope. The fluorescence peak wavelength of individual LH2 complexes was found to abruptly move between quasi-stable levels differing by up to 30 nm. These spectral shifts either to the blue or to the red were accompanied by a broadening and decrease of the intensity of the fluorescence spectrum. The frequency and size of these fluorescence peak movements were found to increase linearly with excitation intensity. Using the modified Redfield theory, changes in the realization of the static disorder accounted for the observed changes in spectral shape and intensity. Long lifetimes of the quasi-stable states suggest large free energy barriers between the different realizations.
authors.affiliation: Department of Biophysics and Physics of Complex Systems, Division of Physics and Astronomy, Faculty of Sciences, Vrije Universiteit, De Boelelaan 1081, 1081 HV Amsterdam, The Netherlands. danielis@nat.vu.nl
authors.forename: Danielis
authors.initials: D
authors.lastname: Rutkauskas
authors.forename: Vladimir
authors.initials: V
authors.lastname: Novoderezkhin
authors.forename: Richard J
authors.initials: RJ
authors.lastname: Cogdell
authors.forename: Rienk
authors.initials: R
authors.lastname: van Grondelle
mesh_terms: D001426:Bacterial Proteins / Q000737:chemistry*; D006358:Hot Temperature; D008027:Light; D045342:Light-Harvesting Protein Complexes / Q000737:chemistry*; D018613:Microscopy, Confocal / Q000379:methods / Q000706:statistics & numerical data; D017711:Nonlinear Dynamics; D016011:Normal Distribution; D017785:Photons; D012241:Rhodopseudomonas / Q000737:chemistry*; D013050:Spectrometry, Fluorescence / Q000379:methods / Q000706:statistics & numerical data; D013696:Temperature; D013816:Thermodynamics
chemical_list: C081521:B800-850 light-harvesting complex, bacteria; D001426:Bacterial Proteins; D045342:Light-Harvesting Protein Complexes