title: Excitation energy transfer in the LHC-II trimer: a model based on the new 2.72 A structure.
abstract: Energy transfer of the light harvesting complex LHC-II trimer, extracted from spinach, was studied in the Q(y) region at room temperature by femtosecond transient absorption spectroscopy. Configuration interaction exciton method [Linnanto et al. (1999) J Phys Chem B 103: 8739-8750] and 2.72 A structural information reported by Liu et al. was used to calculate spectroscopic properties and excitation energy transfer rates of the complex. Site energies of the pigments and coupling constants of pigment pairs in close contact were calculated by using a quantum chemical configuration interaction method. Gaussian random variation of the diagonal and off-diagonal exciton matrix elements was used to account for inhomogeneous broadening. Rate calculations included only the excitonic states initially excited and probed in the experiments. A kinetic model was used to simulate time and wavelength dependent absorption changes after excitation on the blue side of the Q(y) transition and compared to experimentally recorded rates. Analysis of excitonic wavefunctions allowed identification of pigments initially excited and probed into later. It was shown that excitation of the blue side of the Q(y) band of a single LHC-II complex results in energy transfer from chlorophyll b's of the lumenal side to chlorophyll a's located primarly on one of the monomers of the stromal side.
authors.affiliation: Physical Chemistry Laboratory, University of Jyväskylä, P.O. Box 35, Jyväskylä, 40014, Finland. linnanto@cc.jyu.fi
authors.forename: Juha
authors.initials: J
authors.lastname: Linnanto
authors.forename: Jari
authors.initials: J
authors.lastname: Martiskainen
authors.forename: Viivi
authors.initials: V
authors.lastname: Lehtovuori
authors.forename: Janne
authors.initials: J
authors.lastname: Ihalainen
authors.forename: Robertas
authors.initials: R
authors.lastname: Kananavicius
authors.forename: Roberto
authors.initials: R
authors.lastname: Barbato
authors.forename: Jouko
authors.initials: J
authors.lastname: Korppi-Tommola
mesh_terms: D000042:Absorption; D004735:Energy Transfer; D045342:Light-Harvesting Protein Complexes / Q000737:chemistry*; D008954:Models, Biological
chemical_list: D045342:Light-Harvesting Protein Complexes