The development of XFELs has opened up opportunities for studying the dynamics of biological systems beyond what is possible at synchrotron radiation (SR) sources. Intense XFEL pulses enable us to apply both x-ray diffraction and spectroscopic techniques to dilute systems or protein crystals. By taking advantage of ultra-bright femtosecond x-ray pulses, one can also collect the data under functional conditions of temperature and pressure, in a time-resolved manner, after initiating reactions, and follow chemical dynamics during catalytic reactions and electron transfer. Such an approach is particularly beneficial for biological materials and aqueous solution samples that are susceptible to x-ray radiation damage. We have developed spectroscopy and diffraction techniques necessary to fully utilize the capability of the XFEL x-rays for a wide-variety of metalloenzymes, and to study their chemistry under functional conditions (room temperature, ambient pressure). One of such methods is simultaneous data collection for x-ray crystallography and x-ray spectroscopy (Figure), to look at overall structural changes of proteins and chemical changes at metal catalytic sites [1-5]. The other method is soft x-ray absorption spectroscopy of metalloenzymes by developing a spectrometer capable of studying dilute biological systems under ambient conditions [6]. We have used the above techniques to study the water oxidation reaction of Photosystem II multi-subunit protein complex. We will present the progress of this research. References: [1] Kern et al. (2012) PNAS 109, 9721-9726. [2] Alonso-Mori et al. (2012) PNAS 109 19103-19107. [3] Kern et al (2013) Science 340, 491-495. [4] Kern et al (2014) Nat. Comm. 5, 5371. [5] Hattne et al. (2014) Nat. Methods 11, 545-548. [6] Mitzner et al. (2013) J. Phys. Chem. Lett. 4, 3641.

X-ray crystallography and spectroscopy for studying metalloenzymes using XFELs

251st National Meeting (2016)

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