A Model of spin catalysis in bacterial photosynthetic reaction centres

A model of influence of non-heme Fe²⁺ ion on kinetics of electron transfer between quinone anion-radicals Q_A⁻ and Q_B⁻ in bacterial reaction centres is proposed and investigated. Physical mechanism of the influence is associated with singlet-triplet transitions in Q_A⁻Q_B⁻ Pair caused by interactions with paramagnetic Fe²⁺. The model incorporates exchange couplings between the particles and zero-field splittings in high-spin Fe²⁺. These interactions are shown to catalyze electron transfer in triplet pairs and alter the reaction yield significantly.