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Title: Elementary Energy Transfer Pathways in Allochromatium vinosum Photosynthetic Membranes

Abstract

Allochromatium vinosum (formerly Chromatium vinosum) purple bacteria are known to adapt their light-harvesting strategy during growth according to environmental factors such as temperature and average light intensity. Under low light illumination or low ambient temperature conditions, most of the LH2 complexes in the photosynthetic membranes form a B820 exciton with reduced spectral overlap with LH1. To elucidate the reason for this light and temperature adaptation of the LH2 electronic structure, we performed broadband femtosecond transient absorption spectroscopy as a function of excitation wavelength in A. vinosum membranes. A target analysis of the acquired data yielded individual rate constants for all relevant elementary energy transfer (ET) processes. We found that the ET dynamics in high-light-grown membranes was well described by a homogeneous model, with forward and backward rate constants independent of the pump wavelength. Thus, the overall B800→B850→B890→ Reaction Center ET cascade is well described by simple triexponential kinetics. In the low-light-grown membranes, we found that the elementary backward transfer rate constant from B890 to B820 was strongly reduced compared with the corresponding constant from B890 to B850 in high-light-grown samples. The ET dynamics of low-light-grown membranes was strongly dependent on the pump wavelength, clearly showing that the excitation memory ismore » not lost throughout the exciton lifetime. The observed pump energy dependence of the forward and backward ET rate constants suggests exciton diffusion via B850→ B850 transfer steps, making the overall ET dynamics nonexponential. Our results show that disorder plays a crucial role in our understanding of low-light adaptation in A. vinosum.« less

Authors:
; ; ; ; ; ; ;
Publication Date:
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) (SC-22)
OSTI Identifier:
1370784
DOE Contract Number:  
SC0001035
Resource Type:
Journal Article
Journal Name:
Biophysical Journal
Additional Journal Information:
Journal Volume: 109; Journal Issue: 9; 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 0006-3495
Publisher:
Elsevier
Country of Publication:
United States
Language:
English
Subject:
59 BASIC BIOLOGICAL SCIENCES; solar (fuels), photosynthesis (natural and artificial), biofuels (including algae and biomass), bio-inspired, charge transport, membrane, synthesis (novel materials), synthesis (self-assembly)

Citation Formats

Lüer, Larry, Carey, Anne-Marie, Henry, Sarah, Maiuri, Margherita, Hacking, Kirsty, Polli, Dario, Cerullo, Giulio, and Cogdell, Richard J. Elementary Energy Transfer Pathways in Allochromatium vinosum Photosynthetic Membranes. United States: N. p., 2015. Web. doi:10.1016/j.bpj.2015.09.008.
Lüer, Larry, Carey, Anne-Marie, Henry, Sarah, Maiuri, Margherita, Hacking, Kirsty, Polli, Dario, Cerullo, Giulio, & Cogdell, Richard J. Elementary Energy Transfer Pathways in Allochromatium vinosum Photosynthetic Membranes. United States. https://doi.org/10.1016/j.bpj.2015.09.008
Lüer, Larry, Carey, Anne-Marie, Henry, Sarah, Maiuri, Margherita, Hacking, Kirsty, Polli, Dario, Cerullo, Giulio, and Cogdell, Richard J. Sun . "Elementary Energy Transfer Pathways in Allochromatium vinosum Photosynthetic Membranes". United States. https://doi.org/10.1016/j.bpj.2015.09.008.
@article{osti_1370784,
title = {Elementary Energy Transfer Pathways in Allochromatium vinosum Photosynthetic Membranes},
author = {Lüer, Larry and Carey, Anne-Marie and Henry, Sarah and Maiuri, Margherita and Hacking, Kirsty and Polli, Dario and Cerullo, Giulio and Cogdell, Richard J.},
abstractNote = {Allochromatium vinosum (formerly Chromatium vinosum) purple bacteria are known to adapt their light-harvesting strategy during growth according to environmental factors such as temperature and average light intensity. Under low light illumination or low ambient temperature conditions, most of the LH2 complexes in the photosynthetic membranes form a B820 exciton with reduced spectral overlap with LH1. To elucidate the reason for this light and temperature adaptation of the LH2 electronic structure, we performed broadband femtosecond transient absorption spectroscopy as a function of excitation wavelength in A. vinosum membranes. A target analysis of the acquired data yielded individual rate constants for all relevant elementary energy transfer (ET) processes. We found that the ET dynamics in high-light-grown membranes was well described by a homogeneous model, with forward and backward rate constants independent of the pump wavelength. Thus, the overall B800→B850→B890→ Reaction Center ET cascade is well described by simple triexponential kinetics. In the low-light-grown membranes, we found that the elementary backward transfer rate constant from B890 to B820 was strongly reduced compared with the corresponding constant from B890 to B850 in high-light-grown samples. The ET dynamics of low-light-grown membranes was strongly dependent on the pump wavelength, clearly showing that the excitation memory is not lost throughout the exciton lifetime. The observed pump energy dependence of the forward and backward ET rate constants suggests exciton diffusion via B850→ B850 transfer steps, making the overall ET dynamics nonexponential. Our results show that disorder plays a crucial role in our understanding of low-light adaptation in A. vinosum.},
doi = {10.1016/j.bpj.2015.09.008},
url = {https://www.osti.gov/biblio/1370784}, journal = {Biophysical Journal},
issn = {0006-3495},
number = 9,
volume = 109,
place = {United States},
year = {2015},
month = {11}
}