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A novel BioXAS technique with sub-millisecond time resolution to track oxidation state and structural changes at biological metal centers 

J. Synchrotron Rad. (2005). 12, 35–44

[BioXAS] Time-resolved BioXAS on the Mn-complex of photosynthesis at 18°C. (A) Mn XANES spectra spaced by 500 μs (symbols) during the S3→S0 transition. (B) X-ray transient at 6553 eV at 200 μs resolution (arrow, laser flash). (C) Fourier-transformed S3-state EXAFS measured within 200 ms after the laser flash.
X-ray absorption spectroscopy (XAS) to study metal cofactors in enzymes is an increasingly important tool in structural biology. Frequently, characterization of short-lived reaction intermediates is a decisive step in unraveling the catalytic mechanism. A novel approach for time-resolved BioXAS to trace intermediates is described. For the first time, XANES and EXAFS spectra were obtained, for the tetra-manganese complex of oxygenic photosynthesis, within micro- to milliseconds after population of semi-stable states by laser-flash excitation at room temperature. Now the road is open for “real-time” BioXAS investigations.
M. Haumann, C. Müller, P. Liebisch, T. Neisius and H. Dau