Light-induced structural changes and the site of O=O bond formation in PSII caught by XFEL

Seeing the light reaction

23 August 2017

Fast electron laser pulses are helping unravel the precise mechanism by which plants capture energy from sunlight.

Okayama University researchers co-led a study of Photosystem II, the vast protein that handles the photosynthetic step in which light drives the oxidation of water to release molecular oxygen.

The team analyzed the protein using X-ray free electron lasers (XFEL), firing a powerful femtosecond — just one quadrillionth of a second — pulse of electrons at the protein. The electrons bounce off the atoms in the protein; by measuring the electron scatter pattern, the team can work backward to calculate where all the protein’s atoms are, revealing its structure.

Using flashes of light to simulate sunlight, followed by precisely timed XFEL pulses, the researchers captured before-and-after images of the protein during oxygen formation. Comparing the two images, they identified the key atomic motions within the protein as the oxygen molecule was formed, pinpointing the probable spot where the molecule is made.

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References

1. Nature 543, 131– 135 (2017). doi: 10.1038/nature21400