How the molecular structure determines the flow of excitation energy in plant light-harvesting complex II

T. Renger, Mohamed Madjet, A. Knorr, F. Müh

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Abstract

Excitation energy transfer in the light-harvesting complex II of higher plants is modeled using excitonic couplings and local transition energies determined from structure-based calculations recently (Müh et al., 2010). A theory is introduced that implicitly takes into account protein induced dynamic localization effects of the exciton wavefunction between weakly coupled optical and vibronic transitions of different pigments. Linear and non-linear optical spectra are calculated and compared with experimental data reaching qualitative agreement. High-frequency intramolecular vibrational degrees of freedom are found important for ultrafast subpicosecond excitation energy transfer between chlorophyll (Chl) b and Chl. a, since they allow for fast dissipation of the excess energy. The slower ps component of this transfer is due to the monomeric excited state of Chl. b 605. The majority of exciton relaxation in the Chl. a spectral region is characterized by slow ps exciton equilibration between the Chl. a domains within one layer and between the lumenal and stromal layers in the 10-20. ps time range. Subpicosecond exciton relaxation in the Chl. a region is only found within the terminal emitter domain (Chls a 610/611/612) and within the Chl. a 613/614 dimer. Deviations between measured and calculated exciton state life times are obtained for the intermediate spectral region between the main absorbance bands of Chl. a and Chl. b that indicate that besides Chl. b 608 another pigment should absorb there. Possible candidates, so far not identified by structure-based calculations, but by fitting of optical spectra and mutagenesis studies, are discussed. Additional mutagenesis studies are suggested to resolve this issue.

Original languageEnglish
Pages (from-to)1497-1509
Number of pages13
JournalJournal of Plant Physiology
Volume168
Issue number12
DOIs
Publication statusPublished - 15 Aug 2011
Externally publishedYes

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Keywords

  • Bottleneck states
  • Dynamic localization
  • Exciton transfer
  • Generalized Förster theory
  • Modified Redfield theory
  • Site energies
  • Vibronic transitions

ASJC Scopus subject areas

  • Plant Science
  • Physiology
  • Agronomy and Crop Science

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