Collecting and analyzing diffraction data from multiple crystals

Recent years have witnessed a marked revival of multiple crystal data collection and analysis methods. This has been brought about in many ways by a proliferation of microfocus beamlines [1] that have provided convenient access to structural biologists who wish to measure from their tiny crystals. Further to this however has been a realization that in some cases careful data collection and analysis of multiple crystal data can replace months if not years of effort in wet labs optimizing crystals to be large enough to yield a single crystal data set. The presentation will briefly discuss recent progress in multiple crystal data collection and analysis and illustrate it with some case studies.

Visualisation of membrane protein crystals using X-ray imaging

The focus in macromolecular crystallography is moving towards even more challenging target proteins that often crystallise on much smaller scales and are frequently mounted in opaque or highly refractive materials.[1,2] It is therefore essential that X-ray beamline technology develops in parallel to accommodate such difficult samples. In this poster the use of X-ray microradiography and microtomography is reported as a tool for crystal visualisation, location and characterization on the macromolecular crystallography beamlines at the Diamond Light Source. The technique is particularly useful for microcrystals, and crystals mounted in opaque materials such as lipidic cubic phase. X-ray diffraction raster scanning can be used in combination with radiography to allow informed decision-making at the beamline prior to diffraction data collection. It is demonstrated that the X-ray dose required for a full tomography measurement is similar to a diffraction grid scan. However, for sample location and shape estimation alone, just a few radiographic projections may be required; hence reducing the dose the crystals will be exposed to prior to the diffraction data collection.[3]

DIALS - a toolbox for diffraction data analysis

DIALS is a collaborative initiative to produce an open source software toolbox encompassing all aspects of diffraction data analysis, with an initial focus on X-ray diffraction data from synchrotrons and free-electron lasers for macromolecular crystallography. DIALS [1] has been developed as a modular plug-in framework that permits flexibility not only in the development of new methods and algorithms but also in the application of these methods to data analysis. DIALS builds on the cctbx [2] in addition to its own dedicated tool-kits. We will present the ideas behind DIALS and give examples of its versatility in permitting the use of several spot-finding and indexing schemes, global refinement and both two and three dimensional integration methods.