Primary acceptor and secondary donors in photosystem II

When Photosystem II spontaneously charge-separates, the critical pheophytin pigment is transiently reduced before metastable reduction of a plastoquinnone. A number of secondary donors can be formed before oxidation of the catalytic manganese cluster occurs. We have identified and quantified many processes involved taking advantage of our new CCD spectrograph. The pheophytin can also be chemically reduced. This process can be followed by circular dichroism and other spectroscopies. Photosytem II, isolated from a range of organisms, shows variations that identify spectral positions and couplings to nearby pigments.