THE PULSED ELECTRON-ELECTRON DOUBLE-RESONANCE AND 2-SPIN ECHO STUDY OF THE ORIENTED OXYGEN-EVOLVING AND MN-DEPLETED PREPARATIONS OF PHOTOSYSTEM-II(1 ELECTRON)

A ''2+1'' electron spin echo method has been applied to measure the an gular orientation of the radius-vector R-DZ joining the redox-active t yrosine residues Y-D and Y-Z in membrane-oriented Mn-depleted preparat ion of photosystem II. The angle between R-DZ and the normal to the ph otosystem II membrane was determined to be 100 degrees+/-2 degrees, wh ere the angle of 0 degrees corresponds to the direction from Y-D towar ds the-stromal side of the membrane, along the membrane normal. A puls ed electron-electron double resonance method has been used to obtain s imilar information for Y-D and Mn cluster in oriented sample of oxygen -evolving photosystem II. The angle between the radius-vector from Y-D to the Mn cluster, R-DMn, and the membrane normal was found to be 110 degrees+/-2 degrees. (C) 1998 American Institute of Physics.