The fe2+ site of photosynthetic reaction centers probed by multiple scattering x-ray absorption fine structure spectroscopy: improving structure resolution in dry matrices.

ABSTRACT: We report on the x-ray absorption fine structure of the Fe(2+) site in photosynthetic reaction centers from Rhodobacter sphaeroides. Crystallographic studies show that Fe(2+) is ligated with four N(epsilon) atoms from four histidine (His) residues and two O(epsilon) atoms from a Glu residue. By considering multiple scattering contributions to the x-ray absorption fine structure function, we improved the structural resolution of the site: His residues were split into two groups, characterized by different Fe-N(epsilon) distances, and two distinct Fe-O(epsilon) bond lengths resolved. The effect of the environment was studied by embedding the reaction centers into a polyvinyl alcohol film and into a dehydrated trehalose matrix. Incorporation into trehalose caused elongation in one of the two

SUBMITTER: Veronesi G 

PROVIDER: S-EPMC2440445 | biostudies-literature | 2008 Jul

REPOSITORIES: biostudies-literature