X-ray phase imaging with the unified modulated pattern analysis of near-field speckles at a laboratory source.

X-ray phase-contrast techniques are powerful methods for discerning features with similar densities, which are normally indistinguishable with conventional absorption contrast. While these techniques are well-established tools at large-scale synchrotron facilities, efforts have increasingly focused on implementations at laboratory sources for widespread use. X-ray speckle-based imaging is one of the phase-contrast techniques with high potential for translation to conventional x-ray systems. It yields phase-contrast, transmission, and dark-field images with high sensitivity using a relatively simple and cost-effective setup tolerant to divergent and polychromatic beams. Recently, we have introduced the unified modulated pattern analysis (UMPA) [Phys. Rev. Lett.118, 203903 (2017)PRLTAO0031-900710.1103/PhysRevLett.118.203903], which further simplifies the translation of x-ray speckle-based imaging to low-brilliance sources. Here, we present the proof-of-principle implementation of UMPA speckle-based imaging at a microfocus liquid-metal-jet x-ray laboratory source.

Bragg coherent diffraction imaging and metrics for radiation damage in protein micro-crystallography.

The proliferation of extremely intense synchrotron sources has enabled ever higher-resolution structures to be obtained using data collected from smaller and often more imperfect biological crystals (Helliwell, 1984). Synchrotron beamlines now exist that are capable of measuring data from single crystals that are just a few micrometres in size. This provides renewed motivation to study and understand the radiation damage behaviour of small protein crystals. Reciprocal-space mapping and Bragg coherent diffractive imaging experiments have been performed on cryo-cooled microcrystals of hen egg-white lysozyme as they undergo radiation damage. Several well established metrics, such as intensity-loss and lattice expansion, are applied to the diffraction data and the results are compared with several new metrics that can be extracted from the coherent imaging experiments. Individually some of these metrics are inconclusive. However, combining metrics, the results suggest that radiation damage behaviour in protein micro-crystals differs from that of larger protein crystals and may allow them to continue to diffract for longer. A possible mechanism to account for these observations is proposed.

Radiation damage in a micron-sized protein crystal studied via reciprocal space mapping and Bragg coherent diffractive imaging.

For laboratory and synchrotron based X-ray sources, radiation damage has posed a significant barrier to obtaining high-resolution structural data from biological macromolecules. The problem is particularly acute for micron-sized crystals where the weaker signal often necessitates the use of higher intensity beams to obtain the relevant data. Here, we employ a combination of techniques, including Bragg coherent diffractive imaging to characterise the radiation induced damage in a micron-sized protein crystal over time. The approach we adopt here could help screen for potential protein crystal candidates for measurement at X-ray free election laser sources.