Kruger, T.P.J. (Tjaart)Van Grondelle, RienkGwizdala, Michal2019-03-262019-04Krüger, T.P.J., Van Grondelle, R. & Gwizdala, M. 2019, 'The role of far-red spectral states in the energy regulation of phycobilisomes', Biochimica et Biophysica Acta (BBA) - Bioenergetics, vol. 1860, no. 4, pp. 341-349.0005-273610.1016/j.bbabio.2019.01.007http://hdl.handle.net/2263/68715The 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.en© 2018 Elsevier B.V. All rights reserved. Notice : this is the author’s version of a work that was accepted for publication in Biochimica et Biophysica Acta - Biomembranes. Changes resulting from the publishing process, such as peer review, editing, corrections, structural formatting, and other quality control mechanisms may not be reflected in this document. A definitive version was subsequently published in Biochimica et Biophysica Acta - Biomembranes, vol. 1860, no. 4, pp. 341-349, 2019. doi : 10.1016/j.bbabio.2019.01.007.Orange carotenoid protein (OCP)Far-red (FR)Fluorescence blinkingLight harvestingNon-photochemical quenchingPhycobilisome (PB)Single molecule spectroscopyPostprint Article