title: Two-Dimensional Spectroscopy of Chlorophyll a Excited-State Equilibration in Light-Harvesting Complex II.
abstract: Excited-state relaxation dynamics and energy-transfer processes in the chlorophyll a (Chl a) manifold of the light-harvesting complex II (LHCII) were examined at physiological temperature using femtosecond two-dimensional electronic spectroscopy (2DES). The experiments were done under conditions free from singlet-singlet annihilation and anisotropic decay. Energy transfer between the different domains of the Chl a manifold was found to proceed on time scales from hundreds of femtoseconds to five picoseconds, before reaching equilibration. No component slower than 10 ps was observed in the spectral equilibration dynamics. We clearly observe the bidirectional (uphill and downhill) energy transfer of the equilibration process between excited states. This bidirectional energy flow, although implicit in the modeling and simulation of the EET processes, has not been observed in any prior transient absorption studies. Furthermore, we identified the spectral forms associated with the different energy transfer lifetimes in the equilibration process.
authors.affiliation: Division of Chemistry and Biological Chemistry, School of Physical and Mathematical Sciences, Nanyang Technological University , 21 Nanyang Link, Singapore 637371.|Biological Research Centre, Hungarian Academy of Sciences , Temesvári körút 62, Szeged 6726, Hungary.
authors.forename: Parveen
authors.initials: P
authors.lastname: Akhtar
authors.affiliation: Division of Chemistry and Biological Chemistry, School of Physical and Mathematical Sciences, Nanyang Technological University , 21 Nanyang Link, Singapore 637371.
authors.forename: Cheng
authors.identifier: http://orcid.org/0000-0001-7635-8621
authors.initials: C
authors.lastname: Zhang
authors.affiliation: Division of Chemistry and Biological Chemistry, School of Physical and Mathematical Sciences, Nanyang Technological University , 21 Nanyang Link, Singapore 637371.
authors.forename: Thanh Nhut
authors.initials: TN
authors.lastname: Do
authors.affiliation: Biological Research Centre, Hungarian Academy of Sciences , Temesvári körút 62, Szeged 6726, Hungary.
authors.forename: Győző
authors.initials: G
authors.lastname: Garab
authors.affiliation: Division of Chemistry and Biological Chemistry, School of Physical and Mathematical Sciences, Nanyang Technological University , 21 Nanyang Link, Singapore 637371.|Biological Research Centre, Hungarian Academy of Sciences , Temesvári körút 62, Szeged 6726, Hungary.
authors.forename: Petar H
authors.initials: PH
authors.lastname: Lambrev
authors.affiliation: Division of Chemistry and Biological Chemistry, School of Physical and Mathematical Sciences, Nanyang Technological University , 21 Nanyang Link, Singapore 637371.
authors.forename: Howe-Siang
authors.identifier: http://orcid.org/0000-0003-2523-106X
authors.initials: HS
authors.lastname: Tan
mesh_terms: D002734:Chlorophyll / Q000737:chemistry*; D000077194:Chlorophyll A; D004735:Energy Transfer; D045342:Light-Harvesting Protein Complexes / Q000737:chemistry*; D019906:Nuclear Magnetic Resonance, Biomolecular; D045322:Photosynthetic Reaction Center Complex Proteins / Q000737:chemistry
chemical_list: D045342:Light-Harvesting Protein Complexes; D045322:Photosynthetic Reaction Center Complex Proteins; D002734:Chlorophyll; D000077194:Chlorophyll A