GENERATION AND TRAPPING OF SINGLET OXYGEN DURING STRONG ILLUMINATION OF A PHOTOSYSTEM-II CORE COMPLEX

Strong illumination of the Photosystem II (PS II) core complex, under aerobic conditions, resulted in rapid inactivation of electron transpo rt activity and pigment photobleaching, which was followed by the degr adation of the D1 polypeptide. Singlet oxygen, which was generated dur ing strong illumination of Photosystem II, reacted with 4-[2-(3-methyl -3-butenyl)] benzoic acid-sodium salt and the products of the reaction were identified by NMR spectroscopy. Exposure of the PS II core compl ex to singlet oxygen, generated chemically in the dark, caused pigment bleaching and a similar degradation of the D1 protein.