A dark state associated to carotenoid distortions (S*) can quench chlorophyll excitation in a Light-Harvesting Complex of plants

Nicoletta Liguoria, Pengqi Xua, Bart van Oorta, Ralph Bockb, Ivo van Stokkuma, Roberta Crocea
a
Department of Physics and Astronomy and Institute for Lasers, Life and Biophotonics, Faculty of Sciences, VU University Amsterdam, De Boelelaan, 1081, 1081, HV, Amsterdam, The Netherlands; bMax-Planck-Institut für Molekulare Pflanzenphysiologie, D-14476 Potsdam-Golm, Germany

Photo-induced oxidation represents a risk for the stability of both natural and artificial light-harvesting complexes (LHCs). In natural LHCs this is prevented via dissipation of the energy absorbed in excess through interactions between their pigments such as chlorophylls (Chls) and carotenoids (Cars) that create fast decay channels[1]. Cars have been proposed as possible internal quenchers, acting by dissipating Chl excitations via their short lived S1 low-energy state[2, 3]. We purified monomeric LHCs from a mutant of Nicotiana tabacum where astaxanthin is the only Car species. These LHCs are constitutively quenched. Femtosecond spectroscopy and target analysis revealed that the quenching proceeds via energy transfer to a short-lived (~8ps) astaxantin state, identified as S*. Thus, the S* state, previously reported to result from distortion of Cars, may serve in vivo as dissipative channel upon structural changes of the Cars bound to LHCs.

References

[1] Walla, P. J., Holleboom, C.-P. and Fleming, G.R. Non-Photochemical Quenching and Energy Dissipation in Plants, Algae and Cyanobacteria. Springer Netherlands, 2014. 229-243.
[2] Ruban, A. V., Berera, R. Ilioaia, C. Van Stokkum, I.H.M. Kennis, J.T.M. Pascal, A.A. Van Amerongen, H. Robert, B. Horton, P. and Van Grondelle, R. Nature 450, no. 7169 (2007): 575-578.
[3] Staleva, H. Komenda, J. Shukla, M.K. Šlouf, V. Kaňa, R. Polívka, T. Sobotka, R. Nature chemical biology. 2015 Apr 1; 11(4):287-91.