Radiation damage in protein crystallography at X-ray free-electron lasers

Karol Jan Nass

doi:10.1107/s2053273317085497

Abstract

Radiation damage is still the most limiting factor in obtaining high-resolution structures of macromolecules in crystallographic experiments at synchrotrons. With the advent of X-ray free-electron lasers (XFELs) that produce ultrashort and highly intense X-ray pulses, it became possible to outrun most of the radiation-damage processes occurring in the sample during exposure to XFEL radiation. Although this is generally the case, several experimental and theoretical studies have indicated that structures from XFELs may not always be radiation-damage free. This is especially true when higher intensity pulses are used and protein molecules that contain heavy elements in their structures are studied. Here, the radiation-damage mechanisms that occur in samples exposed to XFEL pulses are summarized, results that show indications of radiation damage are reviewed and methods that can partially overcome it are discussed.

Highlights

In order to explore whether undamaged crystal structures can be obtained with higher power densities at the sample, we used two colour x-ray FEL pulses (15 fs) with variable (0-100fs) time delay from the Linac Coherent Light Source (LCLS)
It is expected that a significant fraction of atoms in the crystal become highly ionized during exposure to the tightly focused x-ray FEL pulse
Roome 1, Robert L Shoeman 1, Ilme Schlichting 1

Summary

Introduction

In order to explore whether undamaged crystal structures can be obtained with higher power densities at the sample, we used two colour x-ray FEL pulses (15 fs) with variable (0-100fs) time delay from the Linac Coherent Light Source (LCLS). These pulses were focused to approximately 100 x 100 nm[2] to study radiation damage processes in protein crystals in a time-resolved fashion.

Results

Conclusion