The SFB 1078 kindly invites you to the the following colloquium talk, hosted by Athina Zouni:

Dr. Juno Yano (Molecular Biophysics and Integrated Bioimaging Division, Lawrence Berkeley National Laboratory, Berkeley, CA, USA)

Title: Capturing Reaction Intermediates of the Water Oxidation Reaction in Photosystem II

Abstract: Our group is studying the mechanisms of the catalytic reactions in both natural and inorganic systems. Using various X-ray techniques as tools, we are studying how the catalysts do multielectron reactions, by following the reaction under functional conditions.

We have developed spectroscopy and diffraction techniques necessary to fully utilize the capability of the X-ray Free Electron Laser facilities (XFELs) for a wide variety of metalloenzymes, and to study their chemistry under functional conditions. One of such methods is simultaneous data collection for X-ray crystallography and X-ray spectroscopy, to look at the overall structural changes of proteins and the chemical changes at metal catalytic sites. In parallel to the detection techniques, we have developed an efficient sample delivery method that involves deposition of droplets on a conveyor belt. This 'Droplet on Tape' (DOT) method, delivers a single drop of the crystal suspension or solution sample onto a tape, which then can be transported to the X ray intersection point with a variable delay in time. In the process, the sample is photochemically or chemically activated at various time delays to capture reaction intermediates with crystallography and spectroscopy.

The presentation will cover our group's recent results of metalloenzyme research, in particular, for the study of the water oxidation reaction in natural photosynthesis, using X-ray crystallography and X-ray spectroscopy at XFEL facilities.

References:

Fuller, F. D. et al. Drop-on-demand sample delivery for studying biocatalysts in action

at XFELs, Nat. Methods 14, 443 (2017) DOI:10.1038/nmeth.4195.

Kubin, M. et al. Soft x-ray absorption spectroscopy of metalloproteins and high-valent metal-complexes at room temperature using free-electron lasers, Struct. Dynamics 4, 054307 (2017) DOI: 10.1063/1.4986627.

Kern, J. et al. Structures of the intermediates of Kok’s photosynthetic water oxidation clock. Nature 563, 421 (2018) DOI: 10.1038/s41586-018-0681-2.

Ibrahim, M. et al. Untangling the sequence of events during the S2→ S3 transition in photosystem II and implications for the water oxidation mechanism, Proc. Nat. Acad. Sci. U.S.A., 117, 12624 (2020) DOI: 10.1073/pnas.2000529117.