view article
Figure 3
Changes in the electron density at the OEC during the Kok cycle. The omit map of the oxygen atom OX, which is inserted during the S2 → S3 transition as a bridging oxygen between Mn1 and Ca, is shown in orange. For reference, omit maps constructed by separately omitting the O5 atom are overlaid in blue at the same density levels. The density of OX increases gradually in the S2 → S3 transition and starts to decrease after 500 µs in the S3 → S0 transition with the density below noise level by 2000 µs. The red arrows show the first and last time points where we observe significant OX density. The populations (%) shown are modeled OX occupancies [except at 3F (2000 µs)] in the primary component (see text). Note that because we show the primary component here, the O5 and OEC populations are also changing. Mn atoms are shown as purple, Ca atoms as green and O atoms as red spheres. Color legend for the various σ levels of the omit maps shown are provided in the top-right box.

IUCrJ
Volume 10| Part 6| November 2023| Pages 642-655
ISSN: 2052-2525
https://doi.org/10.1107/S2052252523008928