Investigation of the electronic structure of the primary electron donor in bacterial photosynthesis — Measurements of the anisotropy of the electronic G-tensor using high-field/high-frequency EPR

Cation radicals of the primary electron donor (D + ) in bacterial photosynthesis were investigated by high field, high frequency (95 GHz) EPR. Measurements on frozen solutions of D + , a dimeric π-cation radical, of various organisms ( Rps. viridis, Rb. sphaeroides, Chloroflexus aurantiacus and a heterodimer mutant) are reported, revealing differences in the principal values of the G -tensor. Elements of a theory relating the magnitudes of G principal values to the electronic structure are discussed.