The Position and Orientation of Active Carotenoid in Photosystem II

The distances between YD and active carotenoid have been determined in cyanobacterium (synecochoccus vulcanus) and spinach PSII by pulsed electron double resonance (PELDOR). The observed spectra were analyzed taking into spin distribution of over 30 carbon atoms in the carotenoid molecule. The result of simulations based on the recent crystal structure fitted well with the spectra. The observed spectra for spinach PSII was different, showing the crystal structure of spinach PSII is slightly different from that of cyanobacteria. The ELDOR spectra of YD-YZ radical pair were observed in a cyanobacterium. The result showed the different distance from Spinach PSII.