Antenna organization in green photosynthetic bacteria. 2. Excitation transfer in detached and membrane-bound chlorosomes from Chloroflexus aurantiacus

Journal Article · Tue Dec 29 00:00:00 EST 1987 · Biochemistry; (United States)

DOI:https://doi.org/10.1021/bi00400a024· OSTI ID:5405901

Brune, D C; King, G H; Infosino, A; Steiner, T; Thewalt, M L.W.; Blankenship, R E

The photosynthetic antenna of Chloroflexus aurantiacus includes bacteriochlorophyll (BChl) c/sub 740/ and BChl a/sub 292/, both of which occur in chlorosomes, and B808-866 (containing BChl a/sub 808/ and BChl a/sub 866/), which is membrane-located (subscripts refer to near-infrared absorption maxima in vivo). BChl a/sub 792/ is thought to mediate excitation transfer from BChl c/sub 740/ to BChl a/sub 808/. Lifetimes of fluorescence from BChl c/sub 792/ and BChl a/sub 792/ were measured in isolated and membrane-bound chlorosomes in order to study energy transfer from these pigments. In both preparations, the lifetime of BChl c/sub 740/ fluorescence was at or below the instrumental limit of temporal resolution (about 30-50 ps), implying extremely fast excitation transfer from this pigment. Attempts to disrupt excitation transfer from BChl c/sub 740/, either by conversion of part of this pigment to a monomeric form absorbing at 671 nm or by partial destruction of BChl a/sub 792/ by oxidation with K/sub 3/Fe(CN)/sub 6/, had no discernible effects on the lifetime of BChl c/sub 740/ fluorescence. Most of the fluorescence from BChl a/sub 792/ decayed with a lifetime of 93 +/- 21 ps in membrane-attached chlorosomes and 155 +/- 22 ps in isolated chlorosomes at room temperature. Assuming that the only difference between these preparations is the occurrence of excitation transfer from BChl a/sub 792/ to B808-866, a 41% efficiency was calculated for this process. These results imply either that BChl a/sub 792/ is not an obligatory intermediate in energy transfer from BChl c/sub 7/$/sub 0/ to B808-866 or (more probably) that chlorosome isolation introduces new processes for quenching fluorescence from BChl a/sub 792/.

• Research Organization: Arizona State Univ., Tempe (USA)
• OSTI ID: 5405901
• Journal Information: Biochemistry; (United States), Vol. 26:26
• Country of Publication: United States
• Language: English

Related Subjects

14 SOLAR ENERGY
PHYTOCHROMES
FLUORESCENCE
MOLECULAR STRUCTURE
ABSORPTION SPECTRA
CHLOROPHYLL
EMISSION SPECTRA
PHOTOSYNTHETIC BACTERIA
CARBOXYLIC ACIDS
HETEROCYCLIC ACIDS
HETEROCYCLIC COMPOUNDS
LUMINESCENCE
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PIGMENTS
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140505* - Solar Energy Conversion- Photochemical
Photobiological
& Thermochemical Conversion- (1980-)