title: Minor complexes at work: light-harvesting by carotenoids in the photosystem II antenna complexes CP24 and CP26.
abstract: Plant photosynthesis relies on the capacity of chlorophylls and carotenoids to absorb light. One of the roles of carotenoids is to harvest green-blue light and transfer the excitation energy to the chlorophylls. The corresponding dynamics were investigated here for the first time, to our knowledge, in the CP26 and CP24 minor antenna complexes. The results for the two complexes differ substantially. In CP26 fast transfer (80 fs) occurs from the carotenoid S(2) state to chlorophylls a absorbing at 675 and 678 nm, whereas transfer from the hot S(1) state to the lowest energy chlorophylls is observed in <1 ps. In CP24, energy transfer from the S(2) state leads in 80 fs to the population of chlorophylls b and high-energy chlorophylls a absorbing at 670 nm, whereas the low-energy chlorophylls a are populated only in several picoseconds. The results suggest that CP26 has a structural and functional organization similar to that of LHCII, whereas CP24 differs substantially from the other Lhc complexes, especially regarding the lutein L1 binding domain. No energy transfer from the carotenoid S(1) state to chlorophylls was observed in either complex, suggesting that this state is energetically below the chlorophyll Qy state and therefore may play a role in the quenching of chlorophyll excitations.
authors.affiliation: Faculty of Sciences, Vrije Universiteit Amsterdam, De Boelelaan, Amsterdam, The Netherlands.
authors.forename: Alessandro
authors.initials: A
authors.lastname: Marin
authors.forename: Francesca
authors.initials: F
authors.lastname: Passarini
authors.forename: Ivo H M
authors.initials: IH
authors.lastname: van Stokkum
authors.forename: Rienk
authors.initials: R
authors.lastname: van Grondelle
authors.forename: Roberta
authors.initials: R
authors.lastname: Croce
mesh_terms: D000042:Absorption; D017360:Arabidopsis; D029681:Arabidopsis Proteins / Q000737:chemistry / Q000378:metabolism*; D002338:Carotenoids / Q000737:chemistry / Q000378:metabolism*; D002734:Chlorophyll / Q000378:metabolism; D061146:Chlorophyll Binding Proteins; D004735:Energy Transfer / Q000528:radiation effects; D008027:Light; D045342:Light-Harvesting Protein Complexes / Q000737:chemistry / Q000378:metabolism*; D045332:Photosystem II Protein Complex / Q000737:chemistry / Q000378:metabolism*; D011485:Protein Binding / Q000528:radiation effects; D013057:Spectrum Analysis
chemical_list: D029681:Arabidopsis Proteins; D061146:Chlorophyll Binding Proteins; C490432:LHCB5 protein, Arabidopsis; C529795:Lhcb6 protein, Arabidopsis; D045342:Light-Harvesting Protein Complexes; D045332:Photosystem II Protein Complex; D002734:Chlorophyll; D002338:Carotenoids