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.
AUTOR(ES)
Lubitz, W
RESUMO
Four 15N hyperfine coupling constants, including signs, have been measured by electron nuclear double resonance (ENDOR) and electron nuclear nuclear triple resonance (TRIPLE) for the bacteriochlorophyll a radical cation, BChla+., in vitro and for the light-induced primary donor radical cation, P+.865, in reaction centers of Rhodopseudomonas sphaeroides R-26. A comparison of the data shows that the hyperfine coupling constants have the same sign in both radicals and are, on the average, smaller by a factor of 2 in P+.865. These results provide additional evidence that P+.865 is a bacteriochlorophyll dimer and are in contradiction with the monomer structure of P+.865 recently proposed by O'Malley and Babcock. The reduction factors of the individual 15N couplings, together with the evidence from proton ENDOR data and molecular orbital calculations, indicate a dimer structure in which only two rings (either I and I or III and III) of the bacteriochlorophyll macrocycles overlap.
ACESSO AO ARTIGO
http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=392238Documentos Relacionados
- Structural studies of the primary donor cation radical P870+· in reaction centers of Rhodospirillum rubrum by electron-nuclear double resonance in solution
- Primary electron transfer reactions in modified reaction centers from Rhodopseudomonas sphaeroides
- Isotope effect on electron transfer in reaction centers from Rhodopseudomonas sphaeroides
- Relationship between the oxidation potential and electron spin density of the primary electron donor in reaction centers from Rhodobacter sphaeroides
- Correlation of paramagnetic states and molecular structure in bacterial photosynthetic reaction centers: the symmetry of the primary electron donor in Rhodopseudomonas viridis and Rhodobacter sphaeroides R-26.