Necessity of structural rearrangements for O[sbnd]O bond formation between O5 and W2 in photosystem II

• Numerous aspects of the water oxidation mechanism in photosystem II have not been fully elucidated, especially the O[sbnd]O bond formation pathway. However, a body of experimental evidences have identified the O5 and W2 ligands of the oxygen-evolving complex as the highly probable substrate candidates. In this work, we studied O[sbnd]O bond formation between O5 and W2 based on the native Mn4Ca cluster by density functional calculations. Structural rearrangements before the formation of the S4 state were found as a prerequisite for O[sbnd]O bond formation between O5 and W2, regardless if the suggested pathways involving the typical Mn1(IV)-O[rad] species or the recently proposed Mn4(VII)(O)2 species. Possible alternatives for the S2 → S3 and S3 → S4 transitions accounting for such required rearrangements are discussed. These findings reflect that the structural flexibility of the Mn4Ca cluster is essential to allow structural rearrangements during the catalytic cycle.

Ämnesord

NATURVETENSKAP  -- Kemi -- Fysikalisk kemi (hsv//swe)

NATURAL SCIENCES  -- Chemical Sciences -- Physical Chemistry (hsv//eng)

Nyckelord

Density functional theory

Oxygen-evolving complex

O[sbnd]O bond formation

Structural rearrangement

Substrate water

Binary alloys

Calcium alloys

Bond formation

Catalytic cycles

Experimental evidence

Oxygen-evolving complexes

Photosystem II

Structural flexibilities

Water oxidation

Manganese alloys

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