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Structural studies of the primary donor cation radical P(870) in reaction centers of Rhodospirillum rubrum by electron-nuclear double resonance in solution
- Source :
- Proceedings of the National Academy of Sciences of the United States of America. 81(5)
- Publication Year :
- 1984
-
Abstract
- The light-induced cation radical of the primary electron donor, P 870 +· , in photosynthetic reaction centers from Rhodospirillum rubrum G-9, has been investigated by electron-nuclear double resonance (ENDOR) in liquid aqueous solution. The measured hyperfine coupling constants are assigned to specific molecular positions by partial deuteration. Comparison with the bacteriochlorophyll a cation radical shows different reduction factors of the individual coupling constants deviating from the value 2.0 reported in earlier investigations in frozen solutions. The average of the coupling constants is, however, reduced by a factor very close to 2.0. EPR simulations using the ENDOR coupling constants support a dimer model for P 870 +· with C 2 symmetry, where the two macrocycles are close enough to form a supermolecular orbital resulting in a different distribution of the unpaired electron, compared with the monomeric bacteriochlorophyll a cation radical. Molecular orbital calculations were used to obtain structural information about this dimer.
- Subjects :
- Photosynthetic reaction centre
Electron nuclear double resonance
Multidisciplinary
biology
Chemistry
Rhodospirillum rubrum
Electron donor
biology.organism_classification
Resonance (chemistry)
law.invention
Crystallography
chemistry.chemical_compound
Unpaired electron
Computational chemistry
law
Molecular orbital
Electron paramagnetic resonance
Biological Sciences: Biophysics
Subjects
Details
- ISSN :
- 00278424
- Volume :
- 81
- Issue :
- 5
- Database :
- OpenAIRE
- Journal :
- Proceedings of the National Academy of Sciences of the United States of America
- Accession number :
- edsair.doi.dedup.....0a991df3d13b46bb829e741dc19793ad