Determination of the distance between Yox⋅Z and Q−⋅A in photosystem II by pulsed EPR spectroscopy on light‐induced radical pairs
- 8 January 1999
- journal article
- Published by Wiley in FEBS Letters
- Vol. 442 (1) , 79-82
- https://doi.org/10.1016/s0014-5793(98)01628-7
Abstract
Out-of-phase electron spin echo envelope modulation (ESEEM) spectroscopy was used to determine the distances within two consecutive radical pair states initiated by a laser flash in photosystem II membrane fragments at pH 11. The distance between the spin density centers of the primary electron donor cation radical, P680+*, and the reduced plastoquinone acceptor, QA-*, has been found to be 27.7+/-0.7 A in agreement with previous results. Near room temperature and at high pH, P680+* is reduced by Y(Z), a redox active tyrosine residue, on a sub-microsecond timescale. As a consequence, the subsequent radical pair state, Y(Z)ox*-QA-*, could be investigated after almost complete reduction of P680+* by Y(Z). The determined dipolar electronic spin-spin coupling within the radical pair Y(Z)ox*QA-* corresponds to a distance of 34+/-1 A between the two molecules.Keywords
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