Protein-cofactor interactions in bacterial reaction centers from Rhodobacter sphaeroides R-26: II. Geometry of the hydrogen bonds to the primary quinone formula by 1H and 2H ENDOR spectroscopy.

ABSTRACT: The geometry of the hydrogen bonds to the two carbonyl oxygens of the semiquinone Q(A)(. -) in the reaction center (RC) from the photosynthetic purple bacterium Rhodobacter sphaeroides R-26 were determined by fitting a spin Hamiltonian to the data derived from (1)H and (2)H ENDOR spectroscopies at 35 GHz and 80 K. The experiments were performed on RCs in which the native Fe(2+) (high spin) was replaced by diamagnetic Zn(2+) to prevent spectral line broadening of the Q(A)(. -) due to magnetic coupling with the iron. The principal components of the hyperfine coupling and nuclear quadrupolar coupling tensors of the hydrogen-bonded protons (deuterons) and their principal directions with respect to the quinone axes were obtained by spectral simulations of ENDOR spectra at different magnetic fie

SUBMITTER: Flores M 

PROVIDER: S-EPMC1751397 | biostudies-literature | 2007 Jan

REPOSITORIES: biostudies-literature