Abstract
Pulsed Electron Electron Double Resonance was applied to three spins system to determine the relative positions of electron transfer components in Photosystem II. YZ radical and QA- were trapped after illumination of Tris-treated Zn-substituted PS II for 20 s at 253 K. The time profile observed in spin echo height for YD-YZ-QA system as function of time of application of the second π pusle was analyzed based on the dipolar interaction between three sspins. Using the known distances 38 A for YD-QA and 30 A for YD-YZ, Best fitting was obtained for distance 34 A of YZ-QA. The same method was applied to the YD-QA-ChlZ system. The distance 34 A for ChlZ-QA was obtained.
The results for three spin sytems and the distances and their orientations for two spin sytems were combined. The derived configuration of electron transfer components will be compaired with X-ray data.
