The role of far-red spectral states in the energy regulation of phycobilisomes

Tjaart P.J. Krüger*, Rienk van Grondelle, Michal Gwizdala

*Corresponding author for this work

Research output: Contribution to JournalArticleAcademicpeer-review

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The main light-harvesting pigment-protein complex of cyanobacteria and certain algae is the phycobilisome, which harvests sunlight and regulates the flow of absorbed energy to provide the photochemical reaction centres with a constant energy throughput. At least two light-driven mechanisms of excited energy quenching in phycobilisomes have been identified: the dominant mechanism in many strains of cyanobacteria depends on the orange carotenoid protein (OCP), while the second mechanism is intrinsically available to a phycobilisome and is possibly activated faster than the former. Recent single molecule spectroscopy studies have shown that far-red (FR) emission states are related to the OCP-dependent mechanism and it was proposed that the second mechanism may involve similar states. In this study, we examined the dynamics of simultaneously measured emission spectra and intensities from a large set of individual phycobilisome complexes from Synechocystis PCC 6803. Our results suggest a direct relationship between FR spectral states and thermal energy dissipating states and can be explained by a single phycobilin pigment in the phycobilisome core acting as the site of both quenching and FR emission likely due to the presence of a charge-transfer state. Our experimental method provides a means to accurately resolve the fluorescence lifetimes and spectra of the FR states, which enabled us to quantify a kinetic model that reproduces most of the experimentally determined properties of the FR states.

Original languageEnglish
Pages (from-to)341-349
Number of pages9
JournalBiochimica et Biophysica Acta - Bioenergetics
Issue number4
Early online date2 Feb 2019
Publication statusPublished - 1 Apr 2019


  • Fluorescence blinking
  • Light harvesting
  • Non-photochemical quenching
  • Phycobilisome
  • Single molecule spectroscopy


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