Fluorescence lifetimes of dimers and higher oligomers of bacteriochlorophyll c from Chlorobium limicola |
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Authors: | Timothy P Causgrove Daniel C Brune Robert E Blankenship John M Olson |
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Institution: | (1) Department of Chemistry, Arizona State University, 85287-1604 Tempe, AZ, USA;(2) Center for the Study of Early Events in Photosynthesis, Arizona State University, 85287-1604 Tempe, AZ, USA;(3) Institute of Biochemistry, Odense University, Campusvej 55, DK 5230 Odense M, Denmark |
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Abstract: | Fluorescence lifetimes have been measured for bacteriochlorophyll (BChl) c isolated from Chlorobium limicola in different states of aggregation in non-polar solvents. Two different homologs of BChl c were used, one with an isobutyl group at the 4 position, the other with n-propyl. Species previously identified as dimers (Olson and Pedersen 1990, Photosynth Res, this issue) decayed with lifetimes of 0.64 ns for the isobutyl homolog, 0.71 ns for n-propyl. Decay-associated spectra indicate that the absorption spectrum of the isobutyl dimer is slightly red-shifted from that of the n-propyl dimer. Aggregates absorbing maximally at 710 nm fluoresced with a principal lifetime of 3.1 ns, independent of the homolog used. In CCl4, only the isobutyl homolog forms a 747-nm absorbing oligomer spectrally similar to BChl c in vivo. This oligomer shows non-exponential fluorescence decay with lifetimes of 67 and 19 ps. Because the two components show different excitation spectra, the higher oligomer is probably a mixture of more than one species, both of which absorb at 747 nm.Abbreviations BChl
bacteriochlorophyll
- Chl
chlorophyll
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chi-square
- FWHM
full-width at half-maximum |
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Keywords: | Aggregation bacteriochlorophyll c Chlorobium limicola chlorosomes fluorescence green photosynthetic bacteria |
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