Speaker
Description
X-rays from XFEL sources have had enormous impact on structural biology both through crystallography and
solution scattering. The new methods demonstrated at XFELs focus on measuring the structural dynamics of
biological macromolecules; these motions enable life. The demonstration of serial femtosecond crystallography,
where tens of thousands of small crystals are individually sampled by single, intense x-ray pulses just prior to
their destruction, enabled measurements on room temperature (as opposed to frozen) samples e.g., [1]. The
ability to gain useful diffraction from micron sized protein crystals also opened up the field of millisecond scale
mix-and-inject serial crystallography [2], where the dynamics of reactions involving proteins, including the
creation of reaction intermediates, could be followed with atomic resolution. Solution scattering also benefits
from the high intensity of XFEL sources. Synchrotron small angle x-ray scattering has proven effective at
determining the low-resolution structures of (randomly oriented) biological molecules in solution, including
measurements on ensembles of structures or time-resolved studies that follow large scale conformational
transitions such as folding. Wide angle x-ray scattering, WAXS has the potential to increase the spatial
resolution of solution studies, but the signal strength can be hundreds to thousands of times weaker than SAXS.
The high intensity of the XFEL sources now enables time-resolved WAXS studies e.g. [3, 4], increasing the
spatial resolution of measurements of structural dynamics. The major theme of these experiments is use of
XFEL x-rays to elucidate the structural dynamics of biomolecules, an essential complement to what is known
about the structures of biomolecules. Next generation XFELs offer more pulses, to offset concerns about sample
consumption as well as novel approaches for experiments on biological molecules.
1. Barends, T.R.M., B. Stauch, V. Cherezov, and I. Schlichting, Serial femtosecond crystallography. Nature
Reviews Methods Primers, 2022. 2(1).
2. Pandey, S., et al., Observation of substrate diffusion and ligand binding in enzyme crystals using high-
repetition-rate mix-and-inject serial crystallography. Iucrj, 2021. 8: p. 878-895.
3. Zielinski, K.A., et al., RNA structures and dynamics with A resolution revealed by x-ray free-electron
lasers. Science Advances, 2023. 9(39).
4. Perera, S.M.D.C., et al., Time-Resolved Wide-Angle X-Ray Scattering Reveals Protein Quake in
Rhodopsin Activation. Biophysical Journal, 2017. 112(3): p. 506a-507a