Theg-tensor anisotropy of the triplet state of the primary electron donor in the photosynthetic bacteriumRhodobacter sphaeroides by high-field (95 GHz) EPR

The anisotropy of theg-tensor of the light-induced triplet state of the primary electron donor (D) of the photosynthetic bacteriumRhodobacter sphaeroides is determined by electron-spin-echo-detected electron paramagnetic resonance at 95 GHz. Measurements on frozen solutions of quinone-depleted reaction centers yield g-values along the principal directions of the zero-field splitting tensor (Norris J.R., Budil D.E., Gast P., Chang C.H., ElKabbani O., Schiffer M.: Proc. Natl. Acad. Sci. USA86, 4335–4339, 1989).g-Values determined are: 2.00308, 2.00238, and 2.00138. The deviation from axial symmetry and thez-component of the g-tensor are smaller than observed in the cation radical of D.