Helices are represented as cylinders. Chlorophylls of the D1/D2 reaction center are light green, pheophytins are blue. Chlorophylls of the antenna complexes are dark green, β-carotenes are in orange, hemes are in red. The oxygen evolving center (OEC) is shown as the red, magenta, and cyan balls representing oxygen atoms, Mn ions, and Ca2+ respectively.
The planet's most prolific atmospheric oxygen source has just given up its most detailed mug shot yet. Jim Barber, a professor at Imperial College London, and others have peered into the complex structure and chemistry of Photo-system II's water-splitting manganese and calcium core, the heart of photosynthesis. PSII uses light energy to derive electrons from water for reducing plastoquinone, a mobile electron carrier. Electron microscopy; and more recently X-ray crystallography, have yielded increasingly clearer details of the cluster of four manganese ions and either one or two calcium ions at PSII's center, but without revealing ...
