By Lynn Yarris – Photo-oxidation of water by photosystem II is responsible for most of the oxygen in Earth’s atmosphere.
At the core of photosystem II is a manganese-calcium (Mn4Ca) metalloenzyme complex that when energized by solar photons catalyzes a four photon-step cycle of oxidation states (S0-to-S3) that ultimately yields molecular oxygen. Scientists need to observe intact x-ray crystallography of the Mn4Ca ion in action but the molecule is highly sensitive to radiation.
The LCLS (Linac Coherent Light Source) is the world’s only source of x-rays capable of providing femtosecond pulses at the high intensities that allow intact photosystem II crystals to be imaged before they are destroyed by exposure to the x-ray beams. more> http://tinyurl.com/nlxrcf8