ENDOR and TRIPLE Resonance Investigation of the Primary Donor Cation Radical P 865 +· in Single Crystals of Rhodobacter sphaeroides R-26 Reaction Centers

The primary charge separation step in bacterial photosynthesis from an excited bacteriochlorophyll (BChl) dimer to a bacteriopheophytin with a possible intermediate BChl monomer is controlled both by the three dimensional arrangement and by the electronic structure of the reacting pigments [1,2]. The three dimensional structure of bacterial photosynthetic reaction centers (RC’s) has been determined for R. viridis [3,4] and for Rb. sphaeroides R-26 [5–7] by X-ray diffraction.