Title: Communication: Broad manifold of excitonic states in light-harvesting complex 1 promotes efficient unidirectional energy transfer in vivo

Abstract

In photosynthetic organisms, the pigment-protein complexes that comprise the light-harvesting antenna exhibit complex electronic structures and ultrafast dynamics due to the coupling among the chromophores. In this work, we present absorptive two-dimensional (2D) electronic spectra from living cultures of the purple bacterium, Rhodobacter sphaeroides, acquired using gradient assisted photon echo spectroscopy. Diagonal slices through the 2D lineshape of the LH1 stimulated emission/ground state bleach feature reveal a resolvable higher energy population within the B875 manifold. The waiting time evolution of diagonal, horizontal, and vertical slices through the 2D lineshape shows a sub-100 fs intra-complex relaxation as this higher energy population red shifts. The absorption (855 nm) of this higher lying sub-population of B875 before it has red shifted optimizes spectral overlap between the LH1 B875 band and the B850 band of LH2. Access to an energetically broad distribution of excitonic states within B875 offers a mechanism for efficient energy transfer from LH2 to LH1 during photosynthesis while limiting back transfer. Two-dimensional lineshapes reveal a rapid decay in the ground-state bleach/stimulated emission of B875. This signal, identified as a decrease in the dipole strength of a strong transition in LH1 on the red side of the B875 band, is assigned tomore » the rapid localization of an initially delocalized exciton state, a dephasing process that frustrates back transfer from LH1 to LH2.« less

Authors:

Sohail, Sara H. ^[1]; Dahlberg, Peter D. ^[2]; Allodi, Marco A.  ^[1];

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Massey, Sara C.  ^[1];

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Ting, Po-Chieh ^[1]; Martin, Elizabeth C. ^[3]; Hunter, C. Neil ^[3]; Engel, Gregory S.  ^[1]

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• Search DOE PAGES for ORCID "0000-0002-6740-5243"
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+ Show Author Affiliations

1. Univ. of Chicago, IL (United States). Dept. of Chemistry, Inst. for Biophysical Dynamics, and The James Franck Inst.
2. Univ. of Chicago, IL (United States). Graduate Program in the Biophysical Sciences, Inst. for Biophysical Dynamics, and The James Franck Inst.
3. Univ. of Sheffield (United Kingdom). Dept. of Molecular Biology and Biotechnology

Publication Date:

2017-10-04

Research Org.:

Energy Frontier Research Centers (EFRC) (United States). Photosynthetic Antenna Research Center (PARC)

Sponsoring Org.:

USDOE Office of Science (SC), Basic Energy Sciences (BES)

OSTI Identifier:

1469878

Alternate Identifier(s):

OSTI ID: 1396635

Grant/Contract Number:  

SC0001035; SC 0001035

Resource Type:

Accepted Manuscript

Journal Name:

Journal of Chemical Physics

Additional Journal Information:

Journal Volume: 147; Journal Issue: 13; Related Information: PARC partners with Washington University in St. Louis (lead); University of California, Riverside; University of Glasgow, UK; Los Alamos National Laboratory; University of New Mexico; New Mexico Corsortium; North Carolina State University; Northwestern University; Oak Ridge National Laboratory; University of Pennsylvania; Sandia National Laboratories; University of Sheffield, UK; Journal ID: ISSN 0021-9606

Publisher:

American Institute of Physics (AIP)

Country of Publication:

United States

Language:

English

Subject:

59 BASIC BIOLOGICAL SCIENCES; 14 SOLAR ENERGY; solar (fuels); photosynthesis (natural and artificial); biofuels (including algae and biomass); bio-inspired; charge transport; membrane; synthesis (novel materials); synthesis (self-assembly)