NASA Logo

NTRS

NTRS - NASA Technical Reports Server

Back to Results
Redox regulation of energy transfer efficiency in antennas of green photosynthetic bacteriaThe efficiency of energy transfer from the peripheral chlorosome antenna structure to the membrane-bound antenna in green sulfur bacteria depends strongly on the redox potential of the medium. The fluorescence spectra and lifetimes indicate that efficient quenching pathways are induced in the chlorosome at high redox potential. The midpoint redox potential for the induction of this effect in isolated chlorosomes from Chlorobium vibrioforme is -146 mV at pH 7 (vs the normal hydrogen electrode), and the observed midpoint potential (n = 1) decreases by 60 mV per pH unit over the pH range 7-10. Extraction of isolated chlorosomes with hexane has little effect on the redox-induced quenching, indicating that the component(s) responsible for this effect are bound and not readily extractable. We have purified and partially characterized the trimeric water-soluble bacteriochlorophyll a-containing protein from the thermophilic green sulfur bacterium Chlorobium tepidum. This protein is located between the chlorosome and the membrane. Fluorescence spectra of the purified protein indicate that it also contains groups that quench excitations at high redox potential. The results indicate that the energy transfer pathway in green sulfur bacteria is regulated by redox potential. This regulation appears to operate in at least two distinct places in the energy transfer pathway, the oligomeric pigments in the interior of the chlorosome and in the bacteriochlorophyll a protein. The regulatory effect may serve to protect the cell against superoxide-induced damage when oxygen is present. By quenching excitations before they reach the reaction center, reduction and subsequent autooxidation of the low potential electron acceptors found in these organisms is avoided.
Document ID
20040090289
Acquisition Source
Legacy CDMS
Document Type
Reprint (Version printed in journal)
Authors
Blankenship, R. E.
(Arizona State University Tempe 85287-1604)
Cheng, P.
Causgrove, T. P.
Brune, D. C.
Wang, J.
Date Acquired
August 21, 2013
Publication Date
January 1, 1993
Publication Information
Publication: Photochemistry and photobiology
Volume: 57
Issue: 1
ISSN: 0031-8655
Subject Category
Exobiology
Funding Number(s)
CONTRACT_GRANT: DE-FG-88-ER13969
CONTRACT_GRANT: DE-FG-85ER13388
Distribution Limits
Public
Copyright
Other
Keywords
NASA Discipline Exobiology
NASA Program Exobiology
NASA Discipline Number 52-30
Non-NASA Center

Available Downloads

There are no available downloads for this record.
No Preview Available