The pulsed electron-electron double resonance and "2+1" electron spin echo study of the oriented oxygen-evolving and Mn-depleted preparations of photosystem II

A "2+1" electron spin echo method has been applied to measure the angular orientation of the radius-vector R-DZ joining the redox-active tyrosine residues Y-D and Y-Z in membrane-oriented Mn-depleted preparation of photosystem II. The angle between R-DZ and the normal to the photosystem II membrane was determined to be 100 degrees+/-2 degrees, where the angle of 0 degrees corresponds to the direction from Y-D towards the-stromal side of the membrane, along the membrane normal. A pulsed electron-electron double resonance method has been used to obtain similar 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.