Jul 10, 2014

Taking snapshots of photosynthetic water oxidation using femtosecond X-ray diffraction and spectroscopy

Nature Communications
Jan KernVittal K Yachandra

Abstract

The dioxygen we breathe is formed by light-induced oxidation of water in photosystem II. O2 formation takes place at a catalytic manganese cluster within milliseconds after the photosystem II reaction centre is excited by three single-turnover flashes. Here we present combined X-ray emission spectra and diffraction data of 2-flash (2F) and 3-flash (3F) photosystem II samples, and of a transient 3F' state (250 μs after the third flash), collected under functional conditions using an X-ray free electron laser. The spectra show that the initial O-O bond formation, coupled to Mn reduction, does not yet occur within 250 μs after the third flash. Diffraction data of all states studied exhibit an anomalous scattering signal from Mn but show no significant structural changes at the present resolution of 4.5 Å. This study represents the initial frames in a molecular movie of the structural changes during the catalytic reaction in photosystem II.

  • References55
  • Citations56

References

  • References55
  • Citations56

Mentioned in this Paper

Photopsia
Dioxygen
Plain X-ray
Oxygen Evolving Activity
Oxidation
X-Ray Diffraction
Photosystem II Reaction Center Location
Radiographic Imaging Procedure
Biochemical Turnover
Oxidation-Reduction

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