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Title: On Light-Induced Photoconversion of B800 Bacteriochlorophylls in the LH2 Antenna of the Purple Sulfur Bacterium Allochromatium vinosum

Abstract

The B800-850 LH2 antenna from the photosynthetic purple sulfur bacterium Allochromatium vinosum exhibits an unusual spectral splitting of the B800 absorption band; i.e., two bands are well-resolved at 5 K with maxima at 805 nm (B800 R) and 792 nm (B800 B). To offer more insight into the nature of the B800 bacteriochlorophyll (BChl) a molecules, high-resolution hole-burning (HB) spectroscopy is employed. Both white light illumination and selective laser excitations into B800 R or B800 B lead to B800 R → B800 B phototransformation. Selective excitation into B800 B leads to uncorrelated excitation energy transfer (EET) to B800 R and subsequent B800 R → B800 B phototransformation. The B800 B → B800 R EET time is 0.9 ± 0.1 ps. Excitation at 808.4 nm (into the low-energy side of B800 R) shows that the lower limit of B800 R → B850 EET is about 2 ps, as the B800 R → B800 B phototransformation process could contribute to the corresponding zero-phonon hole width. The phototransformation of B800 R leads to a ~ 200 cm –1 average blue-shift of transition energies, i.e., B800 R changes into B800 B. We argue that it is unlikely that B800-B850 excitonic interactions give rise tomore » a splitting of the B800 band. We postulate that the latter is caused by different protein conformations that can lead to both strong or weak hydrogen bond(s) between B800 pigments and the protein scaffolding. Temperature-dependent absorption spectra of B800, which revealed a well-defined isosbestic point, support a two-site model, likely with strongly and weakly hydrogen-bonded B800 BChls. Thus, BChls contributing to B800 R and B800 B could differ in the position of the proton in the BChl carbonyl-protein hydrogen bond, i.e., proton dynamics along the hydrogen bond may well be the major mechanism of this phototransformation. Yet, the effective tunneling mass is likely larger than the proton mass.« less

Authors:
 [1];  [1];  [2];  [2]; ORCiD logo [1]
  1. Kansas State Univ., Manhattan, KS (United States)
  2. Univ. of Glasgow, Scotland (United Kingdom)
Publication Date:
Research Org.:
Washington Univ., St. Louis, MO (United States). Energy Frontier Research Center (EFRC) Photosynthetic Antenna Research Center (PARC)
Sponsoring Org.:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
OSTI Identifier:
1469903
Grant/Contract Number:  
SC0001035
Resource Type:
Journal Article: Accepted Manuscript
Journal Name:
Journal of Physical Chemistry. B, Condensed Matter, Materials, Surfaces, Interfaces and Biophysical Chemistry
Additional Journal Information:
Journal Volume: 121; Journal Issue: 43; 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 1520-6106
Publisher:
American Chemical Society
Country of Publication:
United States
Language:
English
Subject:
59 BASIC BIOLOGICAL SCIENCES; 37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY; 71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS

Citation Formats

Kell, Adam, Jassas, Mahboobe, Hacking, Kirsty, Cogdell, Richard J., and Jankowiak, Ryszard. On Light-Induced Photoconversion of B800 Bacteriochlorophylls in the LH2 Antenna of the Purple Sulfur Bacterium Allochromatium vinosum. United States: N. p., 2017. Web. doi:10.1021/acs.jpcb.7b06185.
Kell, Adam, Jassas, Mahboobe, Hacking, Kirsty, Cogdell, Richard J., & Jankowiak, Ryszard. On Light-Induced Photoconversion of B800 Bacteriochlorophylls in the LH2 Antenna of the Purple Sulfur Bacterium Allochromatium vinosum. United States. doi:10.1021/acs.jpcb.7b06185.
Kell, Adam, Jassas, Mahboobe, Hacking, Kirsty, Cogdell, Richard J., and Jankowiak, Ryszard. Tue . "On Light-Induced Photoconversion of B800 Bacteriochlorophylls in the LH2 Antenna of the Purple Sulfur Bacterium Allochromatium vinosum". United States. doi:10.1021/acs.jpcb.7b06185. https://www.osti.gov/servlets/purl/1469903.
@article{osti_1469903,
title = {On Light-Induced Photoconversion of B800 Bacteriochlorophylls in the LH2 Antenna of the Purple Sulfur Bacterium Allochromatium vinosum},
author = {Kell, Adam and Jassas, Mahboobe and Hacking, Kirsty and Cogdell, Richard J. and Jankowiak, Ryszard},
abstractNote = {The B800-850 LH2 antenna from the photosynthetic purple sulfur bacterium Allochromatium vinosum exhibits an unusual spectral splitting of the B800 absorption band; i.e., two bands are well-resolved at 5 K with maxima at 805 nm (B800R) and 792 nm (B800B). To offer more insight into the nature of the B800 bacteriochlorophyll (BChl) a molecules, high-resolution hole-burning (HB) spectroscopy is employed. Both white light illumination and selective laser excitations into B800R or B800B lead to B800R → B800B phototransformation. Selective excitation into B800B leads to uncorrelated excitation energy transfer (EET) to B800R and subsequent B800R → B800B phototransformation. The B800B → B800R EET time is 0.9 ± 0.1 ps. Excitation at 808.4 nm (into the low-energy side of B800R) shows that the lower limit of B800R → B850 EET is about 2 ps, as the B800R → B800B phototransformation process could contribute to the corresponding zero-phonon hole width. The phototransformation of B800R leads to a ~ 200 cm–1 average blue-shift of transition energies, i.e., B800R changes into B800B. We argue that it is unlikely that B800-B850 excitonic interactions give rise to a splitting of the B800 band. We postulate that the latter is caused by different protein conformations that can lead to both strong or weak hydrogen bond(s) between B800 pigments and the protein scaffolding. Temperature-dependent absorption spectra of B800, which revealed a well-defined isosbestic point, support a two-site model, likely with strongly and weakly hydrogen-bonded B800 BChls. Thus, BChls contributing to B800R and B800B could differ in the position of the proton in the BChl carbonyl-protein hydrogen bond, i.e., proton dynamics along the hydrogen bond may well be the major mechanism of this phototransformation. Yet, the effective tunneling mass is likely larger than the proton mass.},
doi = {10.1021/acs.jpcb.7b06185},
journal = {Journal of Physical Chemistry. B, Condensed Matter, Materials, Surfaces, Interfaces and Biophysical Chemistry},
issn = {1520-6106},
number = 43,
volume = 121,
place = {United States},
year = {2017},
month = {10}
}

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