title: Spectroscopic characterization of the excitation energy transfer in the fucoxanthin-chlorophyll protein of diatoms.
abstract: We characterized the energy transfer pathways in the fucoxanthin-chlorophyll protein (FCP) complex of the diatom Cyclotella meneghiniana by conducting ultrafast transient absorption measurements. This light harvesting antenna has a distinct pigment composition and binds chlorophyll a (Chl-a), fucoxanthin and chlorophyll c (Chl-c) molecules in a 4:4:1 ratio. We find that upon excitation of fucoxanthin to its S2 state, a significant amount of excitation energy is transferred rapidly to Chl-a. The ensuing dynamics illustrate the presence of a complex energy transfer network that also involves energy transfer from the unrelaxed or 'hot' intermediates. Chl-c to Chl-a energy transfer occurs on a timescale of a 100 fs. We observe no significant spectral evolution in the Chl-a region of the spectrum. We have applied global and target analysis to model the measured excited state dynamics and estimate the spectra of the states involved; the energy transfer network is discussed in relation to the pigment organization of the FCP complex.
authors.affiliation: Department of Physics and Astronomy, Faculty of Sciences, Vrije Universiteit, De Boelelaan 1081, 1081 HV, Amsterdam, The Netherlands. papagian@nat.vu.nl
authors.forename: Emmanouil
authors.initials: E
authors.lastname: Papagiannakis
authors.forename: Ivo
authors.initials: I
authors.lastname: H M van Stokkum
authors.forename: Holger
authors.initials: H
authors.lastname: Fey
authors.forename: Claudia
authors.initials: C
authors.lastname: Büchel
authors.forename: Rienk
authors.initials: R
authors.lastname: van Grondelle
mesh_terms: D020418:Algal Proteins / Q000737:chemistry* / Q000378:metabolism; D002734:Chlorophyll; D017377:Diatoms / Q000737:chemistry*; D004735:Energy Transfer; D007700:Kinetics; D045342:Light-Harvesting Protein Complexes / Q000737:chemistry* / Q000378:metabolism; D013057:Spectrum Analysis; D013696:Temperature; D024341:Xanthophylls
chemical_list: D020418:Algal Proteins; D045342:Light-Harvesting Protein Complexes; D024341:Xanthophylls; C088752:fucoxanthin-, chlorophyll a-c-containing protein; C025164:fucoxanthin; D002734:Chlorophyll