title: Excitation relaxation dynamics and energy transfer in fucoxanthin-chlorophyll a/c-protein complexes, probed by time-resolved fluorescence.
abstract: In algae, light-harvesting complexes contain specific chlorophylls (Chls) and keto-carotenoids; Chl a, Chl c, and fucoxanthin (Fx) in diatoms and brown algae; Chl a, Chl c, and peridinin in photosynthetic dinoflagellates; and Chl a, Chl b, and siphonaxanthin in green algae. The Fx-Chl a/c-protein (FCP) complex from the diatom Chaetoceros gracilis contains Chl c1, Chl c2, and the keto-carotenoid, Fx, as antenna pigments, in addition to Chl a. In the present study, we investigated energy transfer in the FCP complex associated with photosystem II (FCPII) of C. gracilis. For these investigations, we analyzed time-resolved fluorescence spectra, fluorescence rise and decay curves, and time-resolved fluorescence anisotropy data. Chl a exhibited different energy forms with fluorescence peaks ranging from 677 nm to 688 nm. Fx transferred excitation energy to lower-energy Chl a with a time constant of 300fs. Chl c transferred excitation energy to Chl a with time constants of 500-600fs (intra-complex transfer), 600-700fs (intra-complex transfer), and 4-6ps (inter-complex transfer). The latter process made a greater contribution to total Chl c-to-Chl a transfer in intact cells of C. gracilis than in the isolated FCPII complexes. The lower-energy Chl a received excitation energy from Fx and transferred the energy to higher-energy Chl a. This article is part of a special issue entitled: photosynthesis research for sustainability: keys to produce clean energy.
authors: Molecular Photoscience Research Center, Kobe University, Kobe 657-8501, Japan; Graduate School of Science, Kobe University, Kobe 657-8501, Japan; CREST, Japan Science and Technology Agency (JST), Kobe 657-8501, Japan. Electronic address: akimoto@hawk.kobe-u.ac.jp.
authors: Seiji
authors: S
authors: Akimoto
authors: Graduate School of Science, Kobe University, Kobe 657-8501, Japan.
authors: Ayaka
authors: A
authors: Teshigahara
authors: Molecular Photoscience Research Center, Kobe University, Kobe 657-8501, Japan; CREST, Japan Science and Technology Agency (JST), Kobe 657-8501, Japan.
authors: Makio
authors: M
authors: Yokono
authors: Graduate School of Human and Environmental Studies, Kyoto University, Kyoto 606-8501, Japan.
authors: Mamoru
authors: M
authors: Mimuro
authors: Division of Material Science, Graduate School of Science, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8602, Japan.
authors: Ryo
authors: R
authors: Nagao
authors: Faculty of Science, Tokyo University of Science, Tokyo 162-8601 Japan; PRESTO, Japan Science and Technology Agency (JST), Saitama 332-0012, Japan.
authors: Tatsuya
authors: T
authors: Tomo
mesh_terms: D061146:Chlorophyll Binding Proteins / Q000737:chemistry*; D004735:Energy Transfer; D005454:Fluorescence Polarization; D045332:Photosystem II Protein Complex / Q000737:chemistry; D013050:Spectrometry, Fluorescence
chemical_list: D061146:Chlorophyll Binding Proteins; D045332:Photosystem II Protein Complex
keywords: Energy transfer; Fucoxanthin–chlorophyll a/c protein; Light harvesting; Photosynthesis; Time-resolved spectroscopy