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Title: Antenna organization in green photosynthetic bacteria. 1. Oligomeric bacteriochlorophyll c as a model for the 740 nm absorbing bacteriochlorophyll c in Chloroflexus aurantiacus chlorosomes

Abstract

Bacteriochlorophyll (BChl) c was extracted from Chloroflexus aurantiacus and purified by reverse-phase high-pressure liquid chromatography. This pigment consists of a complex mixture of homologues, the major component of which is 4-ethyl-5-methylbacteriochlorophyll c stearyl ester. Unlike previously characterized BChls c, the pigment from C. aurantiacus is a racemic mixture of diastereoisomers with different configurations at the 2a chiral center. Diluting a concentrated methylene chloride solution of BChl c with hexane produces an oligomer with absorption maxima at 740-742 and at 460-462 nm. Both the absorption spectrum and the fluorescence emission spectrum (maximum at 750 nm) of this oligomer closely match those of BChl c in chlorosomes. Further support for this model comes from the ability of alcohols, which disrupt BChl c oligomers by ligating the central Mg atom, to convert BChl c in chlorosomes to a monomeric form when added in low concentrations. The lifetime of fluorescence from the 740 nm absorbing BChl c oligomer is about 80 ps. Although exciton quenching might be unusually fast in the in vitro BChl c oligomer because of its large size and/or the presence of minor impurities, this result suggests that energy transfer from the BChl c antenna in chlorosomes must be very fastmore » if it is to be efficient.« less

Authors:
; ;
Publication Date:
Research Org.:
Arizona State Univ., Tempe (USA)
OSTI Identifier:
5338056
Resource Type:
Journal Article
Journal Name:
Biochemistry; (United States)
Additional Journal Information:
Journal Volume: 26:26
Country of Publication:
United States
Language:
English
Subject:
14 SOLAR ENERGY; PHYTOCHROMES; MOLECULAR STRUCTURE; NUCLEAR MAGNETIC RESONANCE; STEREOCHEMISTRY; ABSORPTION SPECTRA; ABSORPTION SPECTROSCOPY; CHLOROPHYLL; EMISSION SPECTRA; FLUORESCENCE; PHOTOSYNTHETIC BACTERIA; PROTONS; BARYONS; CARBOXYLIC ACIDS; ELEMENTARY PARTICLES; FERMIONS; HADRONS; HETEROCYCLIC ACIDS; HETEROCYCLIC COMPOUNDS; LUMINESCENCE; MAGNETIC RESONANCE; NUCLEONS; ORGANIC ACIDS; ORGANIC COMPOUNDS; ORGANIC NITROGEN COMPOUNDS; PIGMENTS; PORPHYRINS; PROTEINS; RESONANCE; SPECTRA; SPECTROSCOPY; 140505* - Solar Energy Conversion- Photochemical, Photobiological, & Thermochemical Conversion- (1980-)

Citation Formats

Brune, D C, Nozawa, T, and Blankenship, R E. Antenna organization in green photosynthetic bacteria. 1. Oligomeric bacteriochlorophyll c as a model for the 740 nm absorbing bacteriochlorophyll c in Chloroflexus aurantiacus chlorosomes. United States: N. p., 1987. Web. doi:10.1021/bi00400a023.
Brune, D C, Nozawa, T, & Blankenship, R E. Antenna organization in green photosynthetic bacteria. 1. Oligomeric bacteriochlorophyll c as a model for the 740 nm absorbing bacteriochlorophyll c in Chloroflexus aurantiacus chlorosomes. United States. https://doi.org/10.1021/bi00400a023
Brune, D C, Nozawa, T, and Blankenship, R E. 1987. "Antenna organization in green photosynthetic bacteria. 1. Oligomeric bacteriochlorophyll c as a model for the 740 nm absorbing bacteriochlorophyll c in Chloroflexus aurantiacus chlorosomes". United States. https://doi.org/10.1021/bi00400a023.
@article{osti_5338056,
title = {Antenna organization in green photosynthetic bacteria. 1. Oligomeric bacteriochlorophyll c as a model for the 740 nm absorbing bacteriochlorophyll c in Chloroflexus aurantiacus chlorosomes},
author = {Brune, D C and Nozawa, T and Blankenship, R E},
abstractNote = {Bacteriochlorophyll (BChl) c was extracted from Chloroflexus aurantiacus and purified by reverse-phase high-pressure liquid chromatography. This pigment consists of a complex mixture of homologues, the major component of which is 4-ethyl-5-methylbacteriochlorophyll c stearyl ester. Unlike previously characterized BChls c, the pigment from C. aurantiacus is a racemic mixture of diastereoisomers with different configurations at the 2a chiral center. Diluting a concentrated methylene chloride solution of BChl c with hexane produces an oligomer with absorption maxima at 740-742 and at 460-462 nm. Both the absorption spectrum and the fluorescence emission spectrum (maximum at 750 nm) of this oligomer closely match those of BChl c in chlorosomes. Further support for this model comes from the ability of alcohols, which disrupt BChl c oligomers by ligating the central Mg atom, to convert BChl c in chlorosomes to a monomeric form when added in low concentrations. The lifetime of fluorescence from the 740 nm absorbing BChl c oligomer is about 80 ps. Although exciton quenching might be unusually fast in the in vitro BChl c oligomer because of its large size and/or the presence of minor impurities, this result suggests that energy transfer from the BChl c antenna in chlorosomes must be very fast if it is to be efficient.},
doi = {10.1021/bi00400a023},
url = {https://www.osti.gov/biblio/5338056}, journal = {Biochemistry; (United States)},
number = ,
volume = 26:26,
place = {United States},
year = {Tue Dec 29 00:00:00 EST 1987},
month = {Tue Dec 29 00:00:00 EST 1987}
}