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. Author manuscript; available in PMC: 2014 Mar 12.
Published in final edited form as: Biochim Biophys Acta. 2001 Jan 5;1503(0):7–23. doi: 10.1016/s0005-2728(00)00217-6

Fig. 5.

Fig. 5

Proposed model for the active site of the OEC in PS II from the work of Cinco et al. [72]. The model incorporates the finding from the isotropic Sr-substituted PS II studies: Sr2+ (and therefore Ca2+) is intimately linked to the Mn cluster at a distance of ~3.4–3.5 Å. This linkage requires single-atom (oxygen) bridging that can derive from acidic protein residues (aspartate or glutamate), hydroxide, or water. Depicted is one of several possible configurations consistent with the findings of the isotropic Sr EXAFS studies.