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14 N Electron Spin Echo Envelope Modulation (ESEEM) Spectroscopy of the Cation Radical P840 + , the Primary Electron Donor of the Chlorobium limicola Reaction Center
Author(s) -
Bratt Peter J.,
Muhiuddin Irine P.,
Evans Michael C. W.,
Heathcote Peter
Publication year - 1996
Publication title -
photochemistry and photobiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.818
H-Index - 131
eISSN - 1751-1097
pISSN - 0031-8655
DOI - 10.1111/j.1751-1097.1996.tb02416.x
Subject(s) - hyperfine structure , photosynthetic reaction centre , chemistry , bacteriochlorophyll , green sulfur bacteria , spectroscopy , photochemistry , raman spectroscopy , electron paramagnetic resonance , electron , crystallography , nuclear magnetic resonance , electron transfer , atomic physics , photosynthesis , physics , biochemistry , quantum mechanics , optics
The electronic structure of the oxidized primary chlorophyll electron donor, P840 +. , of the green sulfur bacterium Chlorobium limicola has been investigated using electron spin echo envelope modulation (ESEEM) spectroscopy. This ESEEM investigation of the electron spin density distribution in the radical cation P840 +. in membranes isolated from C. limicola confirms that the electron spin is shared eqully between the two bacteriochlorophyll a molecules. Observation of the small hyperfine couplings to the ring nitrogens by ESEEM gives results that are in agreement with those obtained from ENDOR measurements (S. E. J. Rigby, R. Thapar, M. C. W. Evans and P. Heathcote, FEBS Lett. 350,24–28, 1994) of the large hyperfine couplings to the methyl group protons. These results in combination with the Raman spectroscopy of P840 (U. Feiler, D. Albouy, B. Robert and T. A. Mattioli, Biochemistry 34,11099–11105, 1995) all indicate that the reaction center of green sulfur photosynthetic bacteria is functionally a protein homodimer providing a symmetrical protein environment for the primary electron donor.