TRANSIENT SPIN STATES IN THE PRIMARY PROCESSES OF PHOTOSYNTHESIS

The role of the first stabilized charge separated state, P(+.)Q(-.), g enerated in the course of the primary processes in photosynthesis is d iscussed. In particular, the adaptation of the properties of Q(-.) to the functional requirements in different types of photosynthetic react ion centers is considered. Time resolved EPR is shown to be very well- suited for the characterization of P(+.)Q(-.) and that important struc tural and functional properties of the radical pair can be obtained fr om such data. The most recent spectroscopic information is presented a nd evaluated with the aim of correlating differences in the observed c haracteristics of the quinone acceptor with differences in the various types of photosynthetic reaction centers. It is suggested that the na ture of the acceptors following the primary quinone (either an exchang eable quinone or a series of iron-sulfur centers) has a marked influen ce on the nature of the quinone binding.