Recent developments in research on water oxidation by photosystem II

Photosynthetic water oxidation chemistry at the unique manganese–calcium complex of photosystem II (PSII) is of fundamental importance and serves as a paragon in the development of efficient synthetic catalysts. A recent crystal structure of PSII shows the atoms of the water-oxidizing complex; its Mn4CaO5 core resembles inorganic manganese–calcium oxides. Merging of crystallographic and spectroscopic information reverses radiation-induced modifications at the Mn-complex in silico and facilitates discussion of the OO bond chemistry. Coordinated proton movements are promoted by a water network connecting the Mn4CaO5 core with the oxidant, a tyrosine radical and one possibly mobile chloride ion. A basic reaction-cycle model predicts an alternating proton and electron removal from the catalytic site, which facilitates energetically efficient water oxidation.

► A stunning 1.9 Å structure shows the atoms of the water-oxidizing complex. ► Spectroscopic information reverses radiation-induced modifications in-silico. ► Coordinated proton movements in water networks may promote electron transfer. ► Alternating proton and electron removal facilitates water oxidation.