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.