Search

Acquisition of X‐ray crystallographic data is always accompanied by structural degradation owing to the absorption of energy. The application of high‐fluency X‐ray sources to large biomolecules has increased the importance of finding ways to curtail the onset of X‐ray‐induced damage. A significant effort has been under way with the aim of identifying strategies for protecting protein structure. A comprehensive model is presented that has the potential to explain, both qualitatively and quantitatively, the structural changes induced in crystalline protein at ∼100 K. The first step is to consider the qualitative question: what are the radiation‐induced intermediates and expected end products? The aim of this paper is to assist in optimizing these strategies through a fundamental understanding of radiation physics and chemistry, with additional insight provided by theoretical calculations performed on the many schemes presented. [ABSTRACT FROM AUTHOR]

The European X‐ray Free‐Electron Laser (FEL) became the first operational high‐repetition‐rate hard X‐ray FEL with first lasing in May 2017. Biological structure determination has already benefitted from the unique properties and capabilities of X‐ray FELs, predominantly through the development and application of serial crystallography. The possibility of now performing such experiments at data rates more than an order of magnitude greater than previous X‐ray FELs enables not only a higher rate of discovery but also new classes of experiments previously not feasible at lower data rates. One example is time‐resolved experiments requiring a higher number of time steps for interpretation, or structure determination from samples with low hit rates in conventional X‐ray FEL serial crystallography. Following first lasing at the European XFEL, initial commissioning and operation occurred at two scientific instruments, one of which is the Single Particles, Clusters and Biomolecules and Serial Femtosecond Crystallography (SPB/SFX) instrument. This instrument provides a photon energy range, focal spot sizes and diagnostic tools necessary for structure determination of biological specimens. The instrumentation explicitly addresses serial crystallography and the developing single particle imaging method as well as other forward‐scattering and diffraction techniques. This paper describes the major science cases of SPB/SFX and its initial instrumentation – in particular its optical systems, available sample delivery methods, 2D detectors, supporting optical laser systems and key diagnostic components. The present capabilities of the instrument will be reviewed and a brief outlook of its future capabilities is also described. [ABSTRACT FROM AUTHOR]

The Adaptive Gain Integrating Pixel Detector (AGIPD) is an X‐ray imager, custom designed for the European X‐ray Free‐Electron Laser (XFEL). It is a fast, low‐noise integrating detector, with an adaptive gain amplifier per pixel. This has an equivalent noise of less than 1 keV when detecting single photons and, when switched into another gain state, a dynamic range of more than 104 photons of 12 keV. In burst mode the system is able to store 352 images while running at up to 6.5 MHz, which is compatible with the 4.5 MHz frame rate at the European XFEL. The AGIPD system was installed and commissioned in August 2017, and successfully used for the first experiments at the Single Particles, Clusters and Biomolecules (SPB) experimental station at the European XFEL since September 2017. This paper describes the principal components and performance parameters of the system. A description of the 1 million pixel AGIPD system in use at the SPB beamline of the European XFEL is given. [ABSTRACT FROM AUTHOR]