title: The role of the individual Lhcas in photosystem I excitation energy trapping.
abstract: In this work, we have investigated the role of the individual antenna complexes and of the low-energy forms in excitation energy transfer and trapping in Photosystem I of higher plants. To this aim, a series of Photosystem I (sub)complexes with different antenna size/composition/absorption have been studied by picosecond fluorescence spectroscopy. The data show that Lhca3 and Lhca4, which harbor the most red forms, have similar emission spectra (λ(max) = 715-720 nm) and transfer excitation energy to the core with a relative slow rate of ∼25/ns. Differently, the energy transfer from Lhca1 and Lhca2, the "blue" antenna complexes, occurs about four times faster. In contrast to what is often assumed, it is shown that energy transfer from the Lhca1/4 and the Lhca2/3 dimer to the core occurs on a faster timescale than energy equilibration within these dimers. Furthermore, it is shown that all four monomers contribute almost equally to the transfer to the core and that the red forms slow down the overall trapping rate by about two times. Combining all the data allows the construction of a comprehensive picture of the excitation-energy transfer routes and rates in Photosystem I.
authors.affiliation: Department of Biophysical Chemistry, Groningen Biomolecular Sciences and Biotechnology Institute, University of Groningen, Groningen, The Netherlands.
authors.forename: Emilie
authors.initials: E
authors.lastname: Wientjes
authors.forename: Ivo H M
authors.initials: IH
authors.lastname: van Stokkum
authors.forename: Herbert
authors.initials: H
authors.lastname: van Amerongen
authors.forename: Roberta
authors.initials: R
authors.lastname: Croce
mesh_terms: D017360:Arabidopsis / Q000201:enzymology / Q000235:genetics; D003116:Color; D004735:Energy Transfer; D045342:Light-Harvesting Protein Complexes / Q000235:genetics / Q000378:metabolism*; D009154:Mutation; D017785:Photons; D045331:Photosystem I Protein Complex / Q000235:genetics / Q000378:metabolism*; D013050:Spectrometry, Fluorescence; D013696:Temperature; D013997:Time Factors
chemical_list: D045342:Light-Harvesting Protein Complexes; D045331:Photosystem I Protein Complex