Open AccessStructural studies of the primary donor cation radical P 870 +· in reaction centers of Rhodospirillum rubrum by electron-nuclear double resonance in solution
Author(s) -
Wolfgang Lubitz,
Friedhelm Lendzian,
Hugo Scheer,
J. Gottstein,
M. Plato,
K. Möbius
Publication year - 1984
Publication title -
proceedings of the national academy of sciences of the united states of america
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 5.011
H-Index - 771
eISSN - 1091-6490
pISSN - 0027-8424
DOI - 10.1073/pnas.81.5.1401
Subject(s) - rhodospirillum rubrum , resonance (particle physics) , chemistry , electron nuclear double resonance , electron , photosynthetic reaction centre , primary (astronomy) , nuclear magnetic resonance , photochemistry , physics , electron paramagnetic resonance , atomic physics , nuclear physics , electron transfer , biochemistry , enzyme , astronomy
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.