title: Energy transfer pathways in the CP24 and CP26 antenna complexes of higher plant photosystem II: a comparative study.
abstract: Antenna complexes are key components of plant photosynthesis, the process that converts sunlight, CO2, and water into oxygen and sugars. We report the first (to our knowledge) femtosecond transient absorption study on the light-harvesting pigment-protein complexes CP26 (Lhcb5) and CP24 (Lhcb6) of Photosystem II. The complexes are excited at three different wavelengths in the chlorophyll (Chl) Qy region. Both complexes show a single subpicosecond Chl b to Chl a transfer process. In addition, a reduction in the population of the intermediate states (in the 660-670 nm range) as compared to light-harvesting complex II is correlated in CP26 to the absence of both Chls a604 and b605. However, Chl forms around 670 nm are still present in the Chl a Qy range, which undergoes relaxation with slow rates (10-15 ps). This reduction in intermediate-state amplitude CP24 shows a distinctive narrow band at 670 nm connected with Chls b and decaying to the low-energy Chl a states in 3-5 ps. This 670 nm band, which is fully populated in 0.6 ps together with the Chl a low-energy states, is proposed to originate from Chl 602 or 603. In this study, we monitored the energy flow within two minor complexes, and our results may help elucidate these structures in the future.
authors.affiliation: Faculty of Sciences, Vrije Universiteit Amsterdam, Amsterdam, The Netherlands.
authors.forename: Alessandro
authors.initials: A
authors.lastname: Marin
authors.forename: Francesca
authors.initials: F
authors.lastname: Passarini
authors.forename: Roberta
authors.initials: R
authors.lastname: Croce
authors.forename: Rienk
authors.initials: R
authors.lastname: van Grondelle
mesh_terms: D017360:Arabidopsis / Q000378:metabolism*; D029681:Arabidopsis Proteins / Q000378:metabolism*; D061146:Chlorophyll Binding Proteins; D004735:Energy Transfer; D007700:Kinetics; D045342:Light-Harvesting Protein Complexes / Q000378:metabolism*; D045332:Photosystem II Protein Complex / Q000378:metabolism*; D010860:Pigments, Biological / Q000378:metabolism; D013057:Spectrum Analysis; D013997:Time Factors
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; D010860:Pigments, Biological