Effect of Mn cluster on the formation of superoxide radicals in photoinhibition of photosystem II

To further realize the action of superoxide radicals (O-2(-.)) in photoinhi bition of photosystem II (PS II), we employed 5,5-dimethyl-1-pyrroline-N-ox ide (DMPO) as a spin trap, associated with EPR spectroscopy, to study the e ffect of illumination time on O-2(-.) formation during high light photoinhi bition in PS II membranes and Mn-depleted PS II membranes. Results indicate d that the removal of Mn cluster from PS II membranes has a strong influenc e on the dynamics of superoxide formation. The relative mechanism was also discussed. These novel findings may further promote the studies of the stru cture and function of PS II and the mechanism of photoinhibition.