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

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Abstract
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°±2°, where the angle of 0° 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 D Mn , and the membrane normal was found to be 110°±2°.