Structural studies of the primary donor cation radical P870+· in reaction centers of Rhodospirillum rubrum by electron-nuclear double resonance in solution
AUTOR(ES)
Lubitz, W.
RESUMO
The light-induced cation radical of the primary electron donor, P870+·, 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 P870+· with C2 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.
ACESSO AO ARTIGO
http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=344843Documentos Relacionados
- 15N electron nuclear double resonance of the primary donor cation radical P+.865 in reaction centers of Rhodopseudomonas sphaeroides: additional evidence for the dimer model.
- Copper electron-nuclear double resonance of cytochrome c oxidase.
- Electron-nuclear double resonance spectroscopy (and electron spin-echo envelope modulation spectroscopy) in bioinorganic chemistry
- Electron-nuclear double resonance of the hydrogen peroxide compound of cytochrome c peroxidase: identification of the free radical site with a methionyl cluster.
- An Electron-Nuclear Double Resonance (Endor) Study of the Special Pair Model for Photo-Reactive Chlorophyll in Photosynthesis