Excitation energy transfer kinetics and efficiency in phototrophic green sulfur bacteria

A series of spectroscopic measurements were performed on membrane fractions and detergent-solubilized complexes from the green sulfur bacterium (GSB) Chlorobaculum (Cba.) tepidum. The excitation migration through the entire GSB photosynthetic apparatus cannot be observed upon excitation of membranes...

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Published in:Biochimica et biophysica acta. Bioenergetics 2018-10, Vol.1859 (10), p.1180-1190
Main Authors: Magdaong, Nikki Cecil M., Niedzwiedzki, Dariusz M., Saer, Rafael G., Goodson, Carrie, Blankenship, Robert E.
Format: Article
Language:English
Subjects:
Bacteriochlorophyll
Energy transfer
FMO
Green sulfur bacteria
solar (fuels), photosynthesis (natural and artificial), biofuels (including algae and biomass), bio-inspired, charge transport, membrane, synthesis (novel materials), synthesis (self-assembly)
Transient absorption
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Summary:A series of spectroscopic measurements were performed on membrane fractions and detergent-solubilized complexes from the green sulfur bacterium (GSB) Chlorobaculum (Cba.) tepidum. The excitation migration through the entire GSB photosynthetic apparatus cannot be observed upon excitation of membranes in the chlorosome region at 77 K. In order to observe energy transfer from the Fenna-Matthews-Olson (FMO) protein to the reaction center (RC), FMO was directly excited at ~800 nm in transient absorption experiments. However, interpretation of the results is complicated by the spectral overlap between FMO and the RC. The availability of the Y16F FMO mutant, whose absorption spectrum is drastically different from that of the WT, has enabled the selection of spectral regions where either only FMO or the RC contributes. The application of a directed kinetic modeling approach, or target analysis, revealed the various decay and energy transfer pathways within the pigment-protein complexes. The calculated FMO-to-RC excitation energy transfer efficiencies are approximately 25% and 48% for the Y16F and WT samples, respectively. •Excitation energy transfer in green sulfur bacteria was revisited using wild-type and Y16F FMO mutant samples.•The energetic cascade from chlorosome to the reaction center upon chlorosome excitation was not observed at low temperature.•Simpler absorption profile of Y16F enabled assignment of TA spectral features to components of the photosynthetic apparatus.
ISSN:0005-2728
1879-2650
DOI:10.1016/j.bbabio.2018.07.012