1. Excitation energy transfer in chlorosomes of Chlorobium phaeobacteroides strain CL1401: the role of carotenoids
- Author
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Psencik, Jakub, Ma, Ying-Zhong, Arellano, Juan B., García-Gil, L. Jesús, Holzwarth, Alfred R., and Gillbro, Tomas
- Subjects
Chlorosomes ,energy transfer ,fluorescence excitation ,single-photon timing ,femtosecond spectroscopy ,Bacteriochlorophyll ,Chlorobiaceae ,Carotenoids ,green sulfur bacteria - Abstract
The role of carotenoids in chlorosomes of the green sulfur bacterium Chlorobium phaeobacteroides, containing bacteriochlorophyll (BChl) e and the carotenoid (Car) isorenieratene as main pigments, was studied by steady-state fluorescence excitation, picosecond single-photon timing and femtosecond transient absorption (TA) spectroscopy. In order to obtain information about energy transfer from Cars in this photosynthetic light-harvesting antenna with high spectral overlap between Cars and BChls, Car-depleted chlorosomes, obtained by inhibition of Car biosynthesis by 2-hydroxybiphenyl, were employed in a comparative study with control chlorosomes. Excitation spectra measured at room temperature give an efficiency of 60-70% for the excitation energy transfer from Cars to BChls in control chlorosomes. Femtosecond TA measurements enabled an identification of the excited state absorption band of Cars and the lifetime of their S-1 state was determined to be similar to10 ps. Based on this lifetime, we concluded that the involvement of this state in energy transfer is unlikely. Furthermore, evidence was obtained for the presence of an ultrafast (, Swedish Natural Science Research Council. European Union (Contract FMRX-CT96-0081). Kempe Foundation
- Published
- 2002