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 ce ntres is proposed and investigated. Physical mechanism of the influence is associated with singlet-triplet transitions in Q(A)(-)Q(B)(-) pair caused b y interactions with paramagnetic Fe2+. The model incorporates exchange coup lings between the particles and zero-field splittings in high-spin Fe2+. Th ese interactions are shown to catalyze electron transfer in triplet pairs a nd alter the reaction yield significantly.