Stanford Synchrotron Radiation Lightsource
Date Published: March 31, 2010

Researchers Directly Observe Oxygen Signature from the Oxygen-evolving Complex of Photosynthesis
summary written by Raven Hanna

The advent of photosynthesis gave life forms a new way to capture energy from the sun. The by-product of the success of photosynthesis, an abundance of dioxygen (O2) in our atmosphere allowed aerobic creatures, including humans, to evolve and prosper. This process transformed the history of life on Earth. The oxidation of water to O2 is catalyzed by the oxygen-evolving complex (Mn4OxCa cluster) in the membrane protein, photosystem II (PSII).

A team led by scientists from SLAC and Lawrence Berkeley National Laboratory used SSRL Beam Line 6-2 to directly observe the oxygen x-ray emission signal from the oxygen-evolving complex in PSII. They subjected concentrated spinach samples to x-ray emission spectroscopy (XES), and differentiated the signal of the few oxygen atoms bound to manganese in the oxygen-evolving complex versus the multitude of oxygen atoms in the surrounding protein. They observed changes to the bound-oxygen spectral signature depending on the type of binding using a series of model compounds.

In follow-up experiments, the researchers are trying to follow the water-splitting reaction using the x-ray emission of oxygen in the catalytic active site of PSII. This research was published in the January 18 issue of Angewandte Chemie.

To learn more about this research see the full Scientific Highlight

Yulia Pushkar, Xi Long, Pieter Glatzel, Gary W. Brudvig, G. Charles Dismukes, Terrence J. Collins, Vittal K. Yachandra, Junko Yano, and Uwe Bergmann, Direct Detection of Oxygen Ligation to the Mn4Ca Cluster of Photosystem II by X-ray Emission Spectroscopy, Angew. Chem. Int. Ed.

SLAC National Accelerator Laboratory
Stanford University