title: Role of thermal excitation in ultrafast energy transfer in chlorosomes revealed by two-dimensional electronic spectroscopy.
abstract: Chlorosomes are the largest light harvesting complexes in nature and consist of many bacteriochlorophyll pigments forming self-assembled J-aggregates. In this work, we use two-dimensional electronic spectroscopy (2D-ES) to investigate ultrafast dynamics of excitation energy transfer (EET) in chlorosomes and their temperature dependence. From time evolution of the measured 2D electronic spectra of chlorosomes, we directly map out the distribution of the EET rate among the manifold of exciton states in a 2D energy space. In particular, it is found that the EET rate varies gradually depending on the energies of energy-donor and energy-acceptor states. In addition, from comparative 2D-ES measurements at 77 K and room temperature, we show that the EET rate exhibits subtle dependence on both the exciton energy and temperature, demonstrating the effect of thermal excitation on the EET rate. This observation suggests that active thermal excitation at room temperature prevents the excitation trapping at low-energy states and thus promotes efficient exciton diffusion in chlorosomes at ambient temperature.
authors.affiliation: Department of Chemistry, KAIST, Daejeon 305-701, Republic of Korea. hyotcherl.ihee@kaist.ac.kr.
authors.forename: Sunhong
authors.initials: S
authors.lastname: Jun
authors.forename: Cheolhee
authors.initials: C
authors.lastname: Yang
authors.forename: Tae Wu
authors.initials: TW
authors.lastname: Kim
authors.forename: Megumi
authors.initials: M
authors.lastname: Isaji
authors.forename: Hitoshi
authors.initials: H
authors.lastname: Tamiaki
authors.forename: Hyotcherl
authors.initials: H
authors.lastname: Ihee
authors.forename: Jeongho
authors.initials: J
authors.lastname: Kim
mesh_terms: D001419:Bacteria / Q000378:metabolism; D001426:Bacterial Proteins / Q000737:chemistry* / Q000378:metabolism; D001429:Bacteriochlorophylls / Q000737:chemistry; D004735:Energy Transfer; D045342:Light-Harvesting Protein Complexes / Q000737:chemistry*; D056951:Photoelectron Spectroscopy; D013696:Temperature
chemical_list: D001426:Bacterial Proteins; D001429:Bacteriochlorophylls; D045342:Light-Harvesting Protein Complexes