title: A comparative study of the optical characteristics of intact cells of photosynthetic green sulfur bacteria containing bacteriochlorophyll c, d or e.
abstract: Energy transfer and pigment arrangement in intact cells of the green sulfur bacteria Prosthecochloris aestuarii, Chlorobium vibrioforme and chlorobium phaeovibrioides, containing bacteriochlorophyll (BChl) c, d or e as main light harvesting pigment, respectively, were studied by means of absorption, fluorescence, circular dichroism and linear dichroism spectroscopy at low temperature. The results indicate a very similar composition of the antenna in the three species and a very similar structure of main light harvesting components, the chlorosome and the membrane-bound BChl a protein. In all three species the Qy transition dipoles of BChl c, d or e are oriented approximately parallel to the long axis of the chlorosome. Absorption and fluorescence excitation spectra demonstrate the presence of at least two BChl c-e pools in the chlorosomes of all three species, long-wavelength absorbing BChls being closest to the membrane. In C. phaeovibrioides, energy from BChl e is transferred with an efficiency of 25% to the chlorosomal BChl a at 6 K, whereas the efficiency of transfer from BChl e to the BChl a protein is 10%. These numbers are compatible with the hypothesis that the chlorosomal BChl a is an intermediary in the energy transfer from the chlorosome to the membrane.
authors.affiliation: Department of Biophysics, Huygens Laboratory of the State University, P.O. Box 9504, 2300 RA, Leiden, The Netherlands.
authors.forename: S C
authors.initials: SC
authors.lastname: Otte
authors.forename: J C
authors.initials: JC
authors.lastname: van der Heiden
authors.forename: N
authors.initials: N
authors.lastname: Pfennig
authors.forename: J
authors.initials: J
authors.lastname: Amesz