title: Excitation dynamics in Photosystem I from Chlamydomonas reinhardtii. Comparative studies of isolated complexes and whole cells.
abstract: Identical time-resolved fluorescence measurements with ~3.5-ps resolution were performed for three types of PSI preparations from the green alga, Chlamydomonas reinhardtii: isolated PSI cores, isolated PSI-LHCI complexes and PSI-LHCI complexes in whole living cells. Fluorescence decay in these types of PSI preparations has been previously investigated but never under the same experimental conditions. As a result we present consistent picture of excitation dynamics in algal PSI. Temporal evolution of fluorescence spectra can be generally described by three decay components with similar lifetimes in all samples (6-8ps, 25-30ps, 166-314ps). In the PSI cores, the fluorescence decay is dominated by the two fastest components (~90%), which can be assigned to excitation energy trapping in the reaction center by reversible primary charge separation. Excitation dynamics in the PSI-LHCI preparations is more complex because of the energy transfer between the LHCI antenna system and the core. The average trapping time of excitations created in the well coupled LHCI antenna system is about 12-15ps longer than excitations formed in the PSI core antenna. Excitation dynamics in PSI-LHCI complexes in whole living cells is very similar to that observed in isolated complexes. Our data support the view that chlorophylls responsible for the long-wavelength emission are located mostly in LHCI. We also compared in detail our results with the literature data obtained for plant PSI.
authors: Department of Physics, Adam Mickiewicz University, ul. Umultowska 85, 61-614 Poznań, Poland. Electronic address: w_giera@amu.edu.pl.
authors: Wojciech
authors: W
authors: Giera
authors: Department of Physics, Adam Mickiewicz University, ul. Umultowska 85, 61-614 Poznań, Poland.
authors: Sebastian
authors: S
authors: Szewczyk
authors: Department of Chemistry and Biochemistry, Arizona State University, 1711 S. Rural Rd, Box 871604, Tempe, AZ 85287-1604, USA.
authors: Michael D
authors: MD
authors: McConnell
authors: Department of Physics and Astronomy, Vrije Universiteit, De Boelelaan 1081, 1081 HV Amsterdam, The Netherlands.
authors: Joris
authors: J
authors: Snellenburg
authors: Department of Chemistry and Biochemistry, Arizona State University, 1711 S. Rural Rd, Box 871604, Tempe, AZ 85287-1604, USA.
authors: Kevin E
authors: KE
authors: Redding
authors: Department of Physics and Astronomy, Vrije Universiteit, De Boelelaan 1081, 1081 HV Amsterdam, The Netherlands.
authors: Rienk
authors: R
authors: van Grondelle
authors: Department of Physics, Adam Mickiewicz University, ul. Umultowska 85, 61-614 Poznań, Poland.
authors: Krzysztof
authors: K
authors: Gibasiewicz
mesh_terms: D016825:Chlamydomonas reinhardtii / Q000235:genetics / Q000378:metabolism*; D002734:Chlorophyll / Q000378:metabolism; D045331:Photosystem I Protein Complex / Q000235:genetics / Q000378:metabolism*; D013050:Spectrometry, Fluorescence
chemical_list: D045331:Photosystem I Protein Complex; D002734:Chlorophyll
keywords: Chlamydomonas reinhardtii; Light harvesting complex I; Photosystem I; Red chlorophylls; Streak camera; Time-resolved fluorescence