title: Electronic Structure and Dynamics of Higher-Lying Excited States in Light Harvesting Complex 1 from Rhodobacter sphaeroides.
abstract: Light harvesting in photosynthetic organisms involves efficient transfer of energy from peripheral antenna complexes to core antenna complexes, and ultimately to the reaction center where charge separation drives downstream photosynthetic processes. Antenna complexes contain many strongly coupled chromophores, which complicates analysis of their electronic structure. Two-dimensional electronic spectroscopy (2DES) provides information on energetic coupling and ultrafast energy transfer dynamics, making the technique well suited for the study of photosynthetic antennae. Here, we present 2DES results on excited state properties and dynamics of a core antenna complex, light harvesting complex 1 (LH1), embedded in the photosynthetic membrane of Rhodobacter sphaeroides. The experiment reveals weakly allowed higher-lying excited states in LH1 at 770 nm, which transfer energy to the strongly allowed states at 875 nm with a lifetime of 40 fs. The presence of higher-lying excited states is in agreement with effective Hamiltonians constructed using parameters from crystal structures and atomic force microscopy (AFM) studies. The energy transfer dynamics between the higher- and lower-lying excited states agree with Redfield theory calculations.
authors.forename: Peter D
authors.initials: PD
authors.lastname: Dahlberg
authors.forename: Po-Chieh
authors.initials: PC
authors.lastname: Ting
authors.forename: Sara C
authors.initials: SC
authors.lastname: Massey
authors.affiliation: Department of Molecular Biology and Biotechnology, University of Sheffield , Firth Court, Western Bank, Sheffield S10 2TN, U.K.
authors.forename: Elizabeth C
authors.initials: EC
authors.lastname: Martin
authors.affiliation: Department of Molecular Biology and Biotechnology, University of Sheffield , Firth Court, Western Bank, Sheffield S10 2TN, U.K.
authors.forename: C Neil
authors.initials: CN
authors.lastname: Hunter
authors.forename: Gregory S
authors.initials: GS
authors.lastname: Engel
mesh_terms: D002462:Cell Membrane / Q000378:metabolism; D004583:Electrons; D045342:Light-Harvesting Protein Complexes / Q000737:chemistry* / Q000378:metabolism*; D010788:Photosynthesis; D012242:Rhodobacter sphaeroides / Q000166:cytology / Q000378:metabolism*
chemical_list: D045342:Light-Harvesting Protein Complexes