Excitation dynamics in the LHCII complex of higher plants: modeling based on the 2.72A crystal structure

V. Novoderezhkin, M.A. Palacios, H. van Amerongen, R. van Grondelle

Research output: Contribution to journalArticleAcademicpeer-review

206 Citations (Scopus)

Abstract

We have modeled steady-state spectra and energy-transfer dynamics in the peripheral plant light-harvesting complex LHCII using new structural data (Liu, Z.; Yan, H.; Wang, K.; Kuang, T.; Zhang, J.; Gui, L.; An, X.; Chang, W. Nature. 2004, 428, 287). The dynamics of the chlorophyll (Chl) bChl a transfer and decay of selectively excited "bottleneck" Chl a and b states have been studied by femtosecond pump-probe spectroscopy. We propose an exciton model of the LHCII trimer (with specific site energies) which allows a simultaneous quantitative fit of the absorption, linear-dichroism, steady-state fluorescence spectra, and transient absorption kinetics upon excitation at different wavelengths. In the modeling we use the experimental exciton-phonon spectral density and modified Redfield theory. We have found that fast ba transfer is determined by a good connection of the Chls b to strongly coupled Chl a clusters, i.e., a610-a611-a612 trimer and a602-a603 and a613-a614 dimers. Long-lived components of the energy-transfer kinetics are determined by a quick population of red-shifted Chl b605 and blue-shifted Chl a604 followed by a very slow (3 ps for b605 and 12 ps for a604) flow of energy from these monomeric bottleneck sites to the Chl a clusters. The dynamics within the Chl a region is determined by fast (with time constants down to sub-100 fs) exciton relaxation within the a610-a611-a612 trimer, slower 200-300 fs relaxation within the a602-a603 and a613-a614 dimers, even slower 300-800 fs migration between these clusters, and very slow transfer from a604 to the quasi-equilibrated a sites. The final equilibrium is characterized by predominant population of the a610-a611-a612 cluster (mostly the a610 site). The location of this cluster on the outer side of the LHCII trimer probably provides a good connection with the other subunits of PSII.
Original languageEnglish
Pages (from-to)10493-10504
Number of pages13
JournalThe Journal of Physical Chemistry Part B: Condensed Matter, Materials, Surfaces, Interfaces & Biophysical
Volume109
Issue number20
DOIs
Publication statusPublished - 2005

Keywords

  • light-harvesting-complex
  • transient absorption-spectroscopy
  • ultrafast energy-transfer
  • green plants
  • photosystem-ii
  • a/b protein
  • peak shift
  • binding
  • antenna
  • chlorophylls

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