Download citation
Acta Cryst. (2014). A70, C341
Download citation

link to html
The data collection parameters used in a diffraction experiment have a strong impact on the quality of the acquired data. A careful choice of parameters leads to better data and can make the difference between success and failure in phasing attempts and better data will also result in a more accurate atomic model. The selection of data acquisition parameters has to account for the application of the data in various phasing methods or high-resolution refinement. Furthermore, experimental factors like crystal characteristics and the properties of X-ray source and detector have to be considered. Hybrid Pixel Detectors are now for several years in use in macromolecular crystallography and an increasing number of synchrotron beamlines as well as laboratory instruments are equipped with such detectors. Photon-counting Hybrid Pixel Detectors have fundamentally different characteristics and offer various advantages over other detector technologies. To fully exploit the advantages of Hybrid Pixel Detectors, different data collection strategies than those established for other detector types have to be applied. Fine φ-slicing is a strategy particularly well suited because of the fast readout time and the absence of readout noise. This strategy was systematically investigated collecting a large number of data sets from crystals of four different proteins to investigate the benefit of fine φ-slicing on data quality with a noise-free detector in practice. The results show that fine φ-slicing can substantially improve scaling statistics and anomalous signal. Furthermore, when collecting data in continuous rotation at high frame rates up to hundreds of images per second, quality might be impaired by detector readout. Results on the influence of readout time on data quality will be presented and strategies to easily avoid detrimental effects of detector readout will be discussed.

Download citation
Acta Cryst. (2014). A70, C691
Download citation

link to html
GM/CA@APS operates two insertion-device beamlines, 23ID-B and 23ID-D, and one bending magnet beamline, 23BM-B, in sector 23 of the Advanced Photon Source. We recently integrated a Pilatus3 6M detector - a new generation of large sensitive area detectors based on pixel array detector technology and marketed by Dectris. The sensitive area of the device is 423.6 mm × 434.6 mm. The Pilatus3 features the newly implemented re-triggering mechanism that increases the count-rate capabilities by almost an order of magnitude compared to previous generation Pilatus detectors. The detector installed on beamline 23ID-D is the first Pilatus3 6M with a 1000-micron thick sensor, offering higher efficiency at energies above 12 keV. The fast read-out (0.95 ms) and high speed (up to 100 Hz) of the detector allow shutterless data collection. The detector has been fully integrated into the JBluIce user interface and data processing pipeline at GM/CA. Systematic studies with protein crystals were carried out in order to optimize data collection parameters. Overall data collection speed (frame rate), oscillation width per frame, spindle axis speed, and re-triggering have been studied. Different sets of optimal parameters have been established for crystallographic data collection and for crystal screening with the raster feature (grid scanning). The results of these studies and of performance measurements will be presented. This project and GM/CA @ APS are supported by the National Institute of General Medical Sciences and Cancer Institute of NIH.

Download citation
Acta Cryst. (2014). A70, C692
Download citation

link to html
Since their introduction in 2007, single-photon-counting PILATUS hybrid pixel detectors and MYTHEN micro-strip detectors have transformed synchrotron research by enabling new data acquisition modes and even novel experiments. At the same time data quality has improved due to the noise-free operation and the direct conversion of the X-rays, while millisecond readout time and high-frame rates allow for hitherto unknown data acquisition speed and efficiency. Instant retrigger technology, introduced in 2012 with the PILATUS3 further improves the count-rate capabilities to 107 photons/sec/pixel, allowing single photon counting at brightest synchrotron beamlines. On the other hand, the unique properties of these detectors have also been explored to improve and accelerate diffraction and scattering experiments in the laboratory. The noise-free operation is a key advantage in combination with the low-flux laboratory sources, allowing for high-throughput and optimal data quality. The modular architecture of the detectors and the vacuum-compatibility of the PILATUS detector modules are ideal prerequisites to design specific detector solutions. In-vacuum operation is ideally suited to eliminate all background arising from windows and air, resulting in optimal signal-to-noise ratio. Furthermore, the lowest accessible X-ray energy is no longer limited by windows and air absorption but rather by the beamline spectrum and the detector. The minimal X-ray energy compatible with noise-free counting for the PILATUS is below 2 keV. With EIGER, hybrid pixel detectors will enter into a new realm of spatial and temporal resolution. Continuous read-out with frame rates up to 3000 Hz and a pixel size of 75 µm are ideally suited for all scanning type of imaging experiments, time-resolved and high-throughput experiments as well as for outrunning radiation damage. A short overview of the novel aspects of the detector technology will be given. The main emphasize of the presentation will be on the science enabled by the combination of advanced source, optics and detector instrumentation.

Download citation
Acta Cryst. (2014). A70, C882
Download citation

link to html
The PILATUS was the first Hybrid Pixel Detector available for SAXS. It has transformed data collection by its photon-counting technology, which enables noise-free X-ray detection with high dynamic range and excellent stability at high frame rates. These properties are essential for superior data quality in all scattering experiments, especially for optimal background correction when studying low-concentration samples. Besides optimal data quality at each sampling point, highest resolution is desired in most SAXS experiments both in q-range and in time. The newly developed EIGER pixel detector more than doubles the q-resolution that can be achieved when compared with PILATUS3 for the same sample-to-detector distance. EIGER features a pixel size of only 75 µm (in comparison: PILATUS3 has 172 µm). To characterize the spatial resolution of these detectors, point-spread functions were measured at the PTB laboratory at BESSY II, which show that the resolution is directly proportional to the pixel size with minimal cross talk between neighboring pixels. The EIGER 1M detector allows data acquisition at up to 3'000 frames per second. This enables unprecedented temporal resolution in time-resolved SAXS measurements and increases the speed of novel imaging techniques such as scanning SAXS/WAXS and coherent diffractive imaging applications, allowing images to be recorded faster or with higher spatial resolution. The design of the EIGER detector makes it vacuum compatible. Operation at low X-ray energies and correspondingly large scattering angles is another way of increasing q-resolution and also gives access to the lowest q data near the beam stop. In-vacuum detectors enable measurements with ultra-soft x-rays and thus high q-resolution. Moreover they optimize the data quality in scattering experiments by removing absorption and scatter caused from air and windows. An in-vacuum PILATUS 1M detector has been installed at the BESSY-2 FCM beamline and is applied for SAXS/GI-SAXS measurements at energies from 1.75 to 10 keV. For simultaneous SAXS/WAXS applications covering an even wider q-range, in-vacuum detectors with L-shaped detection surface are under development. These will detect the WAXS signal, while a clearance in the detector permits the direct beam to pass on to a SAXS detector placed at larger distance. These latest detector developments will be presented along with corresponding experimental results.

Download citation
Acta Cryst. (2014). A70, C1597
Download citation

link to html
Entomopoxviruses (EV) produce two types of microcrystals in infected cells: virus-containing spheroids representing their main infectious form; and spindles, bipyramidal crystals of the viral fusolin protein, that contribute to the oral virulence of these viruses. In co-feeding experiments, spindles also enhance the insecticidal activity of unrelated insect pathogens, which suggested their use as bioinsecticide additives. To understand how fusolin contributes to virulence and assembles in vivo, we determined the structures of EV spindles by X-ray microcrystallography using crystals isolated from EV-infected common cockchafers. This structure reveals that fusolin is composed of a fibronectin III domain followed by an extended C-terminal molecular arm (CT). The globular domain is structurally homologous to CBP21, a protein that is secreted by Gram-negative bacteria to degrade chitin as a source of energy. Like CBP21, fusolin has all the hallmarks of a lytic polysaccharide monooxygenase enzyme (LPMOs) with two conserved histidine residues forming a copper binding site and a prominent di-tryptophan motif positioned to bind the planar surface of crystalline chitin. The LPMO domain assembles in vivo into ultra-stable crystals crosslinked by CT. This molecular arm mediates the formation of domain-swapped dimers and their assembly into a crystalline lattice stabilized by a 3-D network of inter-dimer disulfide bonds. Overall, the molecular organization of spindles indicates a mode of action where controlled released of the LPMO domain of fusolin by proteolytic removal of the CT extension leads to disruption of the chitin-rich peritrophic matrix of larvae to facilitate the initial steps of viral invasion of the host.

Download citation
Acta Cryst. (2014). A70, C1802
Download citation

link to html
The STOE DECTRIS Xenocs OpenFactory will take place from 10 to 19 September 2014. Participants receive seven days of intensive training by STOE, DECTRIS and Xenocs staff and guest scientists in cooperation with the IUCr. The training will focus on teaching participants the relevant theoretical skillset as well as giving practical training. In Grenoble, the delegates will spend significant time at the ESRF (European Synchrotron) and will be trained in Small Angle X-ray scattering at Xenocs' headquarters. In Darmstadt, the participants will be trained in Single Crystal and Powder XRD at STOE's headquarter. Delegates will have the opportunity to visit beamlines and interact with scientists at ESRF. Starting on 18 September, all OpenFactory participants will join the STOE annual user meeting. The user meeting is a platform for the exchange of ideas among its participants as well as speeches to highlight recent research results. It will be a unique opportunity for OpenFactory participants to interact with highly experienced XRD users and to build up relevant networks. This presentation and poster will highlight the activity, the focus of the program and present the selected participants for the OpenFactory event. The intention is to update on the status of the OpenFactory, but even more important, to encourage similar activities within and after the International Year of Crystallography. In this context, the presenter will discuss any insights from the applications received, i.e. geographies with particular high interest in the OpenFactory, which could be used to follow up on the OpenFactory with future events.
Follow Acta Cryst. A
Sign up for e-alerts
Follow Acta Cryst. on Twitter
Follow us on facebook
Sign up for RSS feeds