Excitation-Energy Transfer Dynamics of Higher Plant Photosystem I Light-Harvesting Complexes

Emilie Wientjes, Ivo H. M. van Stokkum, Herbert van Amerongen, Roberta Croce*

*Corresponding author for this work

Research output: Contribution to journalArticleAcademicpeer-review

41 Citations (Scopus)
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Abstract

Photosystem I (PSI) plays a major role in the light reactions of photosynthesis. In higher plants, PSI is composed of a core complex and four outer antennas that are assembled as two dimers, Lhca1/4 and Lhca2/3. Time-resolved fluorescence measurements on the isolated dimers show very similar kinetics. The intermonomer transfer processes are resolved using target analysis. They occur at rates similar to those observed in transfer to the PSI core, suggesting competition between the two transfer pathways. It appears that each dimer is adopting various conformations that correspond to different lifetimes and emission spectra. A special feature of the Lhca complexes is the presence of an absorption band at low energy, originating from an excitonic state of a chlorophyll dimer, mixed with a charge-transfer state. These low-energy bands have high oscillator strengths and they are superradiant in both Lhca1/4 and Lhca2/3. This challenges the view that the low-energy charge-transfer state always functions as a quencher in plant Lhc's and it also challenges previous interpretations of PSI kinetics. The very similar properties of the low-energy states of both dimers indicate that the organization of the involved chlorophylls should also be similar, in disagreement with the available structural data.

Original languageEnglish
Pages (from-to)1372-1380
Number of pages9
JournalBiophysical Journal
Volume100
Issue number5
DOIs
Publication statusPublished - 2-Mar-2011

Keywords

  • TIME-RESOLVED FLUORESCENCE
  • PIGMENT-PIGMENT INTERACTIONS
  • FAR-RED FLUORESCENCE
  • GREEN PLANTS
  • ANGSTROM RESOLUTION
  • PSI-LHCI
  • ANTENNA COMPLEXES
  • MUTATION ANALYSIS
  • ROOM-TEMPERATURE
  • PROTEINS

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