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Physical Chemistry

Toward A Better Photosynthesis Mimic

Bioinorganic Chemistry: Scientists achieve the closest structural mimic of the oxygen-evolving complex of photosystem II reported to date

by Bethany Halford
May 11, 2015 | A version of this story appeared in Volume 93, Issue 19

Two catalyst active sites compared side by side.
Credit: Science
The Mn4CaO4 cluster of the oxygen-evolving complex in its protein environment (left) and the new artificial version (right). Mn = purple, Ca = green, O = orange, N = blue, C = yellow; H atoms and pivalic CH3 groups are omitted for clarity.

The protein complex known as photosystem II plays a leading role in photosynthesis. One component of this protein, known as the oxygen-evolving complex, splits water into oxygen along with electrons and protons that are eventually used to convert carbon dioxide into organic compounds. Scientists have long sought to mimic this process by making artificial versions of the metal cluster at the heart of the oxygen-evolving complex. A team led by Chunxi Zhang of the Chinese Academy of Sciences, Hongxing Dong of China’s Harbin Engineering University, and Holger Dau of Free University Berlin now report a version of the metal cluster that’s structurally closer to the natural version than any other mimic that’s been reported to date (Science 2015, DOI: 10.1126/science.aaa6550). The oxygen-evolving complex’s center is made up of a Mn4CaO4 cluster, which has a cubane Mn3CaO4 core and a dangling Mn. In the natural system, the dangling metal is linked to the cubane by two oxo bridges. In the new artificial system, the metal has only one oxo bridge. The researchers say this artificial system is a first step toward even closer mimics.


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