Fig. 7.

A Mn cluster with the µ-oxo bridges and bound H₂O/OH⁻ molecules in the S₂ state; the same color code as in panel (B) is used. B¹⁷O EDNMR spectrum at W-band (94 GHz) obtained from PS II core preparations (T. elongatus) in the S₂ state. The buffer has been exchanged with H¹⁷₂O (90% enrichment) for 30 min (3 ×) in the dark (S₁ state) prior to flash-advancement to the S₂ state (black trace). EDNMR spectra are also shown for H¹⁶₂O buffer, containing only ¹⁴N signals (dark blue trace, ¹⁴N from histidine His332, see Fig. 2C). Three classes of oxygen ligands were assigned: the largest ¹⁷O splitting belongs to the exchangeable µ-oxo bridge O5 (green), the smaller ones to the H₂O/OH⁻ molecules (orange, purple) indicated in the figure.

For further details see (Rapatskiy et al. 2012)