Performance of single-photon-counting PILATUS detector modules

Characterization and calibration of DECTRIS PILATUS3 X CdTe 2M high-Z hybrid pixel detector for high-precision powder diffraction measurements

Silicon-based hybrid photon-counting pixel detectors have become the standard for diffraction experiments of all types at low and moderate X-ray energies. More recently, hybrid pixel detectors with high-Z materials have become available, opening up the benefits of this technology for high-energy diffraction experiments. However, detection layers made of high-Z materials are less perfect than those made of silicon, so care must be taken to correct the data in order to remove systematic errors in detector response introduced by inhomogeneities in the detection layer, in addition to the variation of the response of the electronics. In this paper we discuss the steps necessary to obtain the best-quality powder diffraction data from these detectors, and demonstrate that these data are significantly superior to those acquired with other high-energy detector technologies.

Optimization of three-dimensional electron diffuse scattering data acquisition

The diffraction patterns of crystalline materials with local order contain sharp Bragg reflections as well as highly structured diffuse scattering. In this study, we quantitatively show how the diffuse scattering in three-dimensional electron diffraction (3D ED) data is influenced by various parameters, including the data acquisition mode, the detector type and the use of an energy filter. We found that diffuse scattering data used for quantitative analysis are preferably acquired in selected area electron diffraction (SAED) mode using a CCD and an energy filter. In this study, we also show that the diffuse scattering in 3D ED data can be obtained with a quality comparable to that from single-crystal X-ray diffraction. As electron diffraction requires much smaller crystal sizes than X-ray diffraction, this opens up the possibility to investigate the local structure of many technologically relevant materials for which no crystals large enough for single-crystal X-ray diffraction are available.

A Novel and Reliable Pixel Response Correction Method (DAC-Shifting) for Spectral Photon-Counting CT Imaging

Spectral photon-counting cone-beam computed tomography (CT) imaging is challenged by individual pixel response behaviours, which lead to noisy projection images and subsequent image artefacts like rings. Existing methods to correct for this either use calibration measurements, like signal-to-thickness calibration (STC), or perform a post-processing ring artefact correction of sinogram data or scan reconstructions without taking the pixel response explicitly into account. Here, we present a novel post-processing method (digital-to-analogue converter (DAC)-shifting) which explicitly measures the current pixel response using flat-field images and subsequently corrects the projection data. The DAC-shifting method was evaluated using a repeat series of the spectral photon-counting imaging (Medipix3) of a phantom with different density inserts and iodine K-edge imaging. The method was also compared against polymethyl methacrylate (PMMA)-based STC. The DAC-shifting method was shown to be effective in correcting individual pixel responses and was robust against detector instability; it led to a 47.4% average reduction in CT-number variation in homogeneous materials, with a range of 40.7-55.6%. On the contrary, the STC correction showed varying results; a 13.7% average reduction in CT-number variation, ranging from a 43.7% increase to a 45.5% reduction. In K-edge imaging, DAC-shifting provides a sharper attenuation peak and more uniform CT values, which are expected to benefit iodine concentration quantifications.

Quantifying bunch-mode influence on photon-counting detectors at SPring-8

Count-loss characteristics of photon-counting 2D detectors are demonstrated for eight bunch-modes at SPring-8 through Monte Carlo simulations. As an indicator, the effective maximum count rate was introduced to signify the X-ray intensity that the detector can count with a linearity of 1% or better after applying a count-loss correction in each bunch-mode. The effective maximum count rate is revealed to vary depending on the bunch-mode and the intrinsic dead time of the detectors, ranging from 0.012 to 0.916 Mcps (megacounts per second) for a 120 ns dead time, 0.009 to 0.807 Mcps for a 0.5 µs dead time and 0.020 to 0.273 Mcps for a 3 µs intrinsic detector dead time. Even with equal-interval bunch-modes at SPring-8, the effective maximum count rate does not exceed 1 Mcps pixel-1. In other words, to obtain data with a linearity better than 1%, the maximum intensity of X-rays entering the detector should be reduced to 1 Mcps pixel-1 or less, and, in some cases, even lower, depending on the bunch-mode. When applying count-loss correction using optimized dead times tailored to each bunch-mode, the effective maximum count rate exceeds the values above. However, differences in the effective maximum count rate due to bunch-modes persist. Users of photon-counting 2D detectors are encouraged to familiarize themselves with the count-loss characteristics dependent on bunch-mode, and to conduct experiments accordingly. In addition, when designing the time structure of bunch-modes at synchrotron radiation facilities, it is essential to take into account the impact on experiments using photon-counting 2D detectors.

Structural and mechanistic basis for RiPP epimerization by a radical SAM enzyme

D-Amino acid residues, found in countless peptides and natural products including ribosomally synthesized and post-translationally modified peptides (RiPPs), are critical for the bioactivity of several antibiotics and toxins. Recently, radical S-adenosyl-L-methionine (SAM) enzymes have emerged as the only biocatalysts capable of installing direct and irreversible epimerization in RiPPs. However, the mechanism underpinning this biochemical process is ill-understood and the structural basis for this post-translational modification remains unknown. Here we report an atomic-resolution crystal structure of a RiPP-modifying radical SAM enzyme in complex with its substrate properly positioned in the active site. Crystallographic snapshots, size-exclusion chromatography-small-angle x-ray scattering, electron paramagnetic resonance spectroscopy and biochemical analyses reveal how epimerizations are installed in RiPPs and support an unprecedented enzyme mechanism for peptide epimerization. Collectively, our study brings unique perspectives on how radical SAM enzymes interact with RiPPs and catalyze post-translational modifications in natural products.

Micro- and nanostructure specific X-ray tomography reveals less matrix formation and altered collagen organization following reduced loading during Achilles tendon healing

Recovery of the collagen structure following Achilles tendon rupture is poor, resulting in a high risk for re-ruptures. The loading environment during healing affects the mechanical properties of the tendon, but the relation between loading regime and healing outcome remains unclear. This is partially due to our limited understanding regarding the effects of loading on the micro- and nanostructure of the healing tissue. We addressed this through a combination of synchrotron phase-contrast X-ray microtomography and small-angle X-ray scattering tensor tomography (SASTT) to visualize the 3D organization of microscale fibers and nanoscale fibrils, respectively. The effect of in vivo loading on these structures was characterized in early healing of rat Achilles tendons by comparing full activity with immobilization. Unloading resulted in structural changes that can explain the reported impaired mechanical performance. In particular, unloading led to slower tissue regeneration and maturation, with less and more disorganized collagen, as well as an increased presence of adipose tissue. This study provides the first application of SASTT on soft musculoskeletal tissues and clearly demonstrates its potential to investigate a variety of other collagenous tissues. STATEMENT OF SIGNIFICANCE: Currently our understanding of the mechanobiological effects on the recovery of the structural hierarchical organization of injured Achilles tendons is limited. We provide insight into how loading affects the healing process by using a cutting-edge approach to for the first time characterize the 3D micro- and nanostructure of the regenerating collagen. We uncovered that, during early healing, unloading results in a delayed and more disorganized regeneration of both fibers (microscale) and fibrils (nanoscale), as well as increased presence of adipose tissue. The results set the ground for the development of further specialized protocols for tendon recovery.

Similarity score for screening phase-retrieved maps in X-ray diffraction imaging - characterization in reciprocal space

X-ray diffraction imaging (XDI) is utilized for visualizing the structures of non-crystalline particles in material sciences and biology. In the structural analysis, phase-retrieval (PR) algorithms are applied to the diffraction amplitude data alone to reconstruct the electron density map of a specimen particle projected along the direction of the incident X-rays. However, PR calculations may not lead to good convergence because of a lack of diffraction patterns in small-angle regions and Poisson noise in X-ray detection. Therefore, the PR calculation is still a bottleneck for the efficient application of XDI in the structural analyses of non-crystalline particles. For screening maps from hundreds of trial PR calculations, we have been using a score and measuring the similarity between a pair of retrieved maps. Empirically, probable maps approximating the particle structures gave a score smaller than a threshold value, but the reasons for the effectiveness of the score are still unclear. In this study, the score is characterized in terms of the phase differences between the structure factors of the retrieved maps, the usefulness of the score in screening the maps retrieved from experimental diffraction patterns is demonstrated, and the effective resolution of similarity-score-selected maps is discussed.

Bragg coherent diffraction imaging with the CITIUS charge-integrating detector

The CITIUS detector is a next-generation high-speed X-ray imaging detector. It has integrating-type pixels and is designed to show a consistent linear response at a frame rate of 17.4 kHz, which results in a saturation count rate of over 30 Mcps pixel-1 when operating at an acquisition duty cycle close to 100%, and up to 20 times higher with special extended acquisition modes. Here, its application for Bragg coherent diffraction imaging is demonstrated by taking advantage of the fourth-generation Extremely Brilliant Source of the European Synchrotron (ESRF-EBS, Grenoble, France). The CITIUS detector outperformed a photon-counting detector, similar spatial resolution being achieved (20 ± 6 nm versus 22 ± 9 nm) with greatly reduced acquisition times (23 s versus 200 s). It is also shown how the CITIUS detector can be expected to perform during dynamic Bragg coherent diffraction imaging measurements. Finally, the current limitations of the CITIUS detector and further optimizations for coherent imaging techniques are discussed.

Structural Insight into the Amino Acid Environment of the Two-Domain Laccase's Trinuclear Copper Cluster

Laccases are industrially relevant enzymes. However, their range of applications is limited by their functioning and stability. Most of the currently known laccases function in acidic conditions at temperatures below 60 °C, but two-domain laccases (2D) oxidize some substrates in alkaline conditions and above 70 °C. In this study, we aim to establish the structural factors affecting the alkaline activity of the 2D laccase from Streptomyces griseoflavus (SgfSL). The range of methods used allowed us to show that the alkaline activity of SgfSL is influenced by the polar residues located close to the trinuclear center (TNC). Structural and functional studies of the SgfSL mutants Met199Ala/Asp268Asn and Met199Gly/Asp268Asn revealed that the substitution Asp268Asn (11 Å from the TNC) affects the orientation of the Asn261 (the second coordination sphere of the TNC), resulting in hydrogen-bond-network reorganization, which leads to a change in the SgfSL-activity pH profile. The combination of the Met199Gly/Arg240His and Asp268Asn substitutions increased the efficiency (kcat/KM) of the 2,6-DMP oxidation by 34-fold compared with the SgfSL. Our results extend the knowledge about the structure and functioning of 2D laccases' TNC active sites and open up new possibilities for the directed engineering of laccases.

Lyotropic liquid crystal elastomers for drug delivery

Silicone elastomers like polydimethylsiloxane (PDMS) possess a combination of attractive material and biological properties motivating their widespread use in biomedical applications. Development of elastomers with capacity to deliver active therapeutic substances in the form of drugs is of particular interest to produce medical devices with added functionality. In this work, silicone-based lyotropic liquid crystal elastomers with drug-eluting functionality were developed using PDMS and triblock copolymer (diacrylated Pluronic F127, DA-F127). Various ternary PDMS-DA-F127-H₂O compositions were explored and evaluated. Three compositions were found to have specific properties of interest and were further investigated for their nanostructure, mechanical properties, water retention capacity, and morphology. The ability of the elastomers to encapsulate and release polar and nonpolar substances was demonstrated using vancomycin and ibuprofen as model drugs. It was shown that the materials could deliver both types of drugs with a sustained release profile for up to 6 and 5 days for vancomycin and ibuprofen, respectively. This works demonstrates a lyotropic liquid crystal, silicone-based elastomer with tailorable mechanical properties, water retention capacity and ability to host and release polar and nonpolar active substances.

Time-Resolved Small-Angle X-Ray Scattering of Protein Cage Assembly

Recent improvements in X-ray detectors and synchrotron light sources have made it possible to measure time-resolved small-angle X-ray scattering (TR-SAXS) at millisecond time resolution. As an example, in this chapter we describe the beamline setup, experimental scheme, and the points that should be noted in stopped-flow TR-SAXS experiments for investigating the ferritin assembly reaction.

Structural and Functional Characterization of β-lytic Protease from Lysobacter capsici VKM B-2533T

The crystal structure of the Lysobacter capsici VKM B-2533^T β-lytic protease (Blp), a medicinally promising antimicrobial enzyme, was first solved. Blp was established to possess a folding characteristic of the M23 protease family. The groove of the Blp active site, as compared with that of the LasA structural homologue from Pseudomonas aeruginosa, was found to have amino acid differences. Biochemical analysis revealed no differences in the optimal reaction conditions for manifesting Blp and LasA bacteriolytic activities. At the same time, Blp had a broader range of action against living and autoclaved target cells. The results suggest that the distinction in the geometry of the active site and the charge of amino acid residues that form the active site groove can be important for the hydrolysis of different peptidoglycan types in target cells.

Multi-Scale Investigation of Human Renal Tissue in Three Dimensions

Histopathology as a diagnostic mainstay for tissue evaluation is strictly a 2D technology. Combining and supplementing this technology with 3D imaging has been proposed as one future avenue towards refining comprehensive tissue analysis. To this end, we have developed a laboratory-based X-ray method allowing for the investigation of tissue samples in three dimensions with isotropic volume information. To assess the potential of our method for micro-morphology evaluation, we selected several kidney regions from three patients with cystic kidney disease, obstructive nephropathy and diabetic glomerulopathy. Tissue specimens were processed using our in-house-developed X-ray eosin stain and investigated with a commercial microCT and our in-house-built NanoCT. The microCT system provided overview scans with voxel sizes of [Formula: see text] and the NanoCT was employed for higher resolutions including voxel sizes from [Formula: see text] to 210 nm. We present a methodology allowing for a precise micro-morphologic investigation in three dimensions which is compatible with conventional histology. Advantages of our methodology are its versatility with respect to multi-scale investigations, being laboratory-based, allowing for non-destructive imaging and providing isotropic volume information. We believe, that after future developmental work this method might contribute to advanced multi-modal tissue diagnostics.

SAXSDOG: open software for real-time azimuthal integration of 2D scattering images

In situ small- and wide-angle scattering experiments at synchrotrons often result in massive quantities of data within just seconds. Especially during such beamtimes, processing of the acquired data online, without appreciable delay, is key to obtaining feedback on the failure or success of the experiment. This had led to the development of SAXSDOG, a Python-based environment for real-time azimuthal integration of large-area scattering images. The software is primarily designed for dedicated data pipelines: once a scattering image is transferred from the detector onto the storage unit, it is automatically integrated and pre-evaluated using integral parameters within milliseconds. The control and configuration of the underlying server-based processes is achieved via a graphical user interface, SAXSLEASH, which visualizes the resulting 1D data together with integral classifiers in real time. SAXSDOG further includes a portable `take-home' version for users that runs on standalone computers, enabling its use in laboratories or at the preferred workspace.

X-ray zooming optics for analyzer-based multi-contrast computed tomography

An X-ray analyzer-based optics with a zoom function is proposed for observing various samples with apparent-absorption contrast, phase contrast and scattering contrast. The proposed X-ray optics consists of a collimator crystal and an analyzer crystal arranged in a nondispersive (+, -) geometry with a sample placed between them. For the implementation of the zoom function, an asymmetrically cut crystal in the rotated-inclined geometry was used for the analyzer. Proof-of-principle experiments were performed at the vertical wiggler beamline BL-14B of the Photon Factory. First, the magnification was set to 1×, and then it was zoomed into the optimal magnification (10×). At these magnifications, tri-modal contrast cross-sectional images of a sample were obtained by computed tomography. It was confirmed that the image quality at 10× was superior to that at 1×. This achievement opens up new possibilities for observing an entire sample or regions of interest within a sample at optimal magnification, and is expected to be useful for materials science, condensed matter physics, archeology and biomedical science.

The NIST Vacuum Double-Crystal Spectrometer: A Tool for SI-Traceable Measurement of X-Ray Emission Spectra

The NIST Vacuum Double-Crystal Spectrometer (VDCS) has been modernized and is now capable of recording reference-free wavelength-dispersive spectra in the 2 keV to 12 keV x-ray energy range. The VDCS employs crystals in which the lattice spacings are traceable to the definition of the meter through x-ray optical interferometry with a relative uncertainty ﹤10-⁸. VDCS wavelength determination relies upon precision angle difference measurements for which the encoders of the rotation stages have been calibrated using the circle closure method for accurate, absolute angle measurement. The new vacuum-compatible area detector allows quantification of the aberration functions contributing to the observed line shape and in situ alignment of the crystal optics. This latter procedure is augmented with the use of a thin lamella as the first crystal. With these new techniques, x-ray spectra are registered with the VDCS on an absolute energy scale with a relative uncertainty of 10-⁶.

Engineering the Catalytic Properties of Two-Domain Laccase from Streptomyces griseoflavus Ac-993

Laccases catalyze the oxidation of substrates with the concomitant reduction of oxygen to water. Recently, we found that polar residues located in tunnels leading to Cu2 and Cu3 ions control oxygen entrance (His 165) and proton transport (Arg 240) of two-domain laccase (2D) from Streptomyces griseoflavus (SgfSL). In this work, we have focused on optimizing the substrate-binding pocket (SBP) of SgfSL while simultaneously adjusting the oxygen reduction process. SgfSL variants with three single (Met199Ala, Met199Gly, and Tyr230Ala) and three double amino acid residues substitutions (Met199Gly/His165Ala, His165Ala/Arg240His, Met199Gly/Arg240His) were constructed, purified, and investigated. Combination of substitutions in the SBP and in the tunnel leading to Cu2 ion (Met199Gly/Arg240His) increased SgfSL catalytic activity towards ABTS by 5-fold, and towards 2.6-DMP by 16-fold. The high activity of the Met199Gly/Arg240His variant can be explained by the combined effect of the SBP geometry optimization (Met199Gly) and increased proton flux via the tunnel leading to Cu2 ion (Arg240His). Moreover, the variant with Met199Gly and His165Ala mutations did not significantly increase SgfSL's activity, but led to a drastic shift in the optimal pH of 2.6-DMP oxidation. These results indicate that His 165 not only regulates oxygen access, but it also participates in proton transport in 2D laccases.

Clustering in ferronematics-The effect of magnetic collective ordering

Clustering of magnetic nanoparticles can dramatically change their collective magnetic properties, and it consequently may influence their performance in biomedical and technological applications. Owing to tailored surface modification of magnetic particles such composites represent stable systems. Here, we report ferronematic mixtures that contain anisotropic clusters of mesogen-hybridized cobalt ferrite nanoparticles dispersed in liquid crystal host studied by different experimental methods-magnetization measurements, small-angle X-ray scattering (SAXS), small-angle neutron scattering (SANS), and capacitance measurements. These measurements reveal non-monotonic dependencies of magnetization curves and the Fréedericksz transition on the magnetic nanoparticles concentration. This can be explained by the formation of clusters, whose structures were determined by SAXS measurements. Complementary to the magnetization measurements, SANS measurements of the samples were performed for different magnetic field strengths to obtain information on the orientation of the liquid crystal molecules. We demonstrated that such hybrid materials offer new avenues for tunable materials.

DIALS as a toolkit

The DIALS software for the processing of X‐ray diffraction data is presented, with an emphasis on how the suite may be used as a toolkit for data processing. The description starts with an overview of the history and intent of the toolkit, usage as an automated system, command‐line use, and ultimately how new tools can be written using the API to perform bespoke analysis. Consideration is also made to the application of DIALS to techniques outside of macromolecular X‐ray crystallography.

3D nanoscale analysis of bone healing around degrading Mg implants evaluated by X-ray scattering tensor tomography

The nanostructural adaptation of bone is crucial for its biocompatibility with orthopedic implants. The bone nanostructure also determines its mechanical properties and performance. However, the bone's temporal and spatial nanoadaptation around degrading implants remains largely unknown. Here, we present insights into this important bone adaptation by applying scanning electron microscopy, elemental analysis, and small-angle X-ray scattering tensor tomography (SASTT). We extend the novel SASTT reconstruction method and provide a 3D scattering reciprocal space map per voxel of the sample's volume. From this reconstruction, parameters such as the thickness of the bone mineral particles are quantified, which provide additional information on nanostructural adaptation of bone during healing. We selected a rat femoral bone and a degrading ZX10 magnesium implant as model system, and investigated it over the course of 18 months, using a sham as control. We observe that the bone's nanostructural adaptation starts with an initially fast interfacial bone growth close to the implant, which spreads by a re-orientation of the nanostructure in the bone volume around the implant, and is consolidated in the later degradation stages. These observations reveal the complex bulk bone-implant interactions and enable future research on the related biomechanical bone responses. STATEMENT OF SIGNIFICANCE: Traumatic bone injuries are among the most frequent causes of surgical treatment, and often require the placement of an implant. The ideal implant supports and induces bone formation, while being mechanically and chemically adapted to the bone structure, ensuring a gradual load transfer. While magnesium implants fulfill these requirements, the nanostructural changes during bone healing and implant degradation remain not completely elucidated. Here, we unveil these processes in rat femoral bones with ZX10 magnesium implants and show different stages of bone healing in such a model system.

Imaging of retina cellular and subcellular structures using ptychographic hard X-ray tomography

Ptychographic hard X-ray computed tomography (PXCT) is a recent method allowing imaging with quantitative electron-density contrast. Here, we imaged, at cryogenic temperature and without sectioning, cellular and subcellular structures of a chemically fixed and stained wild-type mouse retina, including axons and synapses, with complete isotropic 3D information over tens of microns. Comparison with tomograms of degenerative retina from a mouse model of retinitis pigmentosa illustrates the potential of this method for analyzing disease processes like neurodegeneration at sub-200 nm resolution. As a non-destructive imaging method, PXCT is very suitable for correlative imaging. Within the outer plexiform layer containing the photoreceptor synapses, we identified somatic synapses. We used a small region inside the X-ray-imaged sample for further high-resolution focused ion beam/scanning electron microscope tomography. The subcellular structures of synapses obtained with the X-ray technique matched the electron microscopy data, demonstrating that PXCT is a powerful scanning method for tissue volumes of more than 60 cells and sensitive enough for identification of regions as small as 200 nm, which remain available for further structural and biochemical investigations.

Combining High-Throughput Synthesis and High-Throughput Protein Crystallography for Accelerated Hit Identification

Protein crystallography (PX) is widely used to drive advanced stages of drug optimization or to discover medicinal chemistry starting points by fragment soaking. However, recent progress in PX could allow for a more integrated role into early drug discovery. Here, we demonstrate for the first time the interplay of high throughput synthesis and high throughput PX. We describe a practical multicomponent reaction approach to acrylamides and -esters from diverse building blocks suitable for mmol scale synthesis on 96-well format and on a high-throughput nanoscale format in a highly automated fashion. High-throughput PX of our libraries efficiently yielded potent covalent inhibitors of the main protease of the COVID-19 causing agent, SARS-CoV-2. Our results demonstrate, that the marriage of in situ HT synthesis of (covalent) libraires and HT PX has the potential to accelerate hit finding and to provide meaningful strategies for medicinal chemistry projects.

Multi-energy reconstructions, central electron temperature measurements, and early detection of the birth and growth of runaway electrons using a versatile soft x-ray pinhole camera at MST

A multi-energy soft x-ray pinhole camera has been designed, built, and deployed at the Madison Symmetric Torus to aid the study of particle and thermal transport, as well as MHD stability physics. This novel imaging diagnostic technique employs a pixelated x-ray detector in which the lower energy threshold for photon detection can be adjusted independently on each pixel. The detector of choice is a PILATUS3 100 K with a 450 μm thick silicon sensor and nearly 100 000 pixels sensitive to photon energies between 1.6 and 30 keV. An ensemble of cubic spline smoothing functions has been applied to the line-integrated data for each time-frame and energy-range, obtaining a reduced standard-deviation when compared to that dominated by photon-noise. The multi-energy local emissivity profiles are obtained from a 1D matrix-based Abel-inversion procedure. Central values of T_e can be obtained by modeling the slope of the continuum radiation from ratios of the inverted radial emissivity profiles over multiple energy ranges with no a priori assumptions of plasma profiles, magnetic field reconstruction constraints, high-density limitations, or need of shot-to-shot reproducibility. In tokamak plasmas, a novel application has recently been tested for early detection, 1D imaging, and study of the birth, exponential growth, and saturation of runaway electrons at energies comparable to 100 × T_e,0; thus, early results are also presented.

Synthesis, structural characterization and antimycobacterial evaluation of several halogenated non-nitro benzothiazinones

8-Nitro-1,3-benzothiazin-4-ones (BTZs), with BTZ043 and PBTZ169 as the most advanced compounds, represent a new class of potent antitubercular agents, which irreversibly inhibit decaprenylphosphoryl-β-d-ribose-2'-epimerase (DprE1), an enzyme crucial for cell wall synthesis in the pathogen Mycobacterium tuberculosis. Synthesis, structural characterization and in vitro testing against Mycobacterium aurum DSM 43999 and M. tuberculosis H₃₇Rv of halogenated 2-(4-ethoxycarbonylpiperazin-1-yl)-1,3-benzothiazin-4-ones lacking a nitro group are reported. X-ray crystallography reveals that the structure of the BTZ scaffold can significantly deviate from planarity. In contrast to recent reports, the results of the present study indicate that further investigation of halogenated non-nitro BTZs for antitubercular activity is less than a promising approach.

Cotton Textile/Iron Oxide Nanozyme Composites with Peroxidase-like Activity: Preparation, Characterization, and Application

At present, both native and immobilized nanoparticles are of great importance in many areas of science and technology. In this paper, we have studied magnetic iron oxide nanoparticles and their aggregates bound on woven cotton textiles employing two simple modification procedures. One modification was based on the treatment of textiles with perchloric-acid-stabilized magnetic fluid diluted with methanol followed by drying. The second procedure was based on the microwave-assisted conversion of ferrous sulfate at high pH followed by drying. The structure and functional properties of these modified textiles were analyzed in detail. Scanning electron microscopy of native and modified textiles clearly showed the presence of iron oxide nanoparticles on the surface of the modified cotton fibers. All of the modified textile materials exhibited light to dark brown color depending on the amount of the bound iron oxide particles. Magnetic measurements showed that the saturation magnetization values reflect the amount of magnetic nanoparticles present in the modified textiles. Small-angle X-ray and neutron scattering measurements were conducted for the detailed structural characterization at the nanoscale of both the native and magnetically modified textiles, and different structural organization of nanoparticles in the two kinds of textile samples were concluded. The textile-bound iron oxide particles exhibited peroxidase-like activity when the N,N-diethyl-p-phenylenediamine sulfate salt was used as a substrate; this nanozyme activity enabled rapid decolorization of crystal violet in the presence of hydrogen peroxide. The deposition of a sufficient amount of iron oxide particles on textiles enabled their simple magnetic separation from large volumes of solutions; if necessary, the magnetic response of the modified textiles can be simply increased by incorporation of a piece of magnetic iron wire. The simplicity of the immobilized nanozyme preparation and the low cost of all the precursors enable its widespread application, such as decolorization and degradation of selected organic dyes and other important pollutants. Other types of textile-bound nanozymes can be prepared and used as low-cost catalysts for a variety of applications.

Highly Permeable Fluorinated Polymer Nanocomposites for Plasmonic Hydrogen Sensing

Hydrogen (H₂) sensors that can be produced en masse with cost-effective manufacturing tools are critical for enabling safety in the emerging hydrogen economy. The use of melt-processed nanocomposites in this context would allow the combination of the advantages of plasmonic hydrogen detection with polymer technology; an approach which is held back by the slow diffusion of H₂ through the polymer matrix. Here, we show that the use of an amorphous fluorinated polymer, compounded with colloidal Pd nanoparticles prepared by highly scalable continuous flow synthesis, results in nanocomposites that display a high H₂ diffusion coefficient in the order of 10^-5 cm² s^-1. As a result, plasmonic optical hydrogen detection with melt-pressed fluorinated polymer nanocomposites is no longer limited by the diffusion of the H₂ analyte to the Pd nanoparticle transducer elements, despite a thickness of up to 100 μm, thereby enabling response times as short as 2.5 s at 100 mbar (≡10 vol. %) H₂. Evidently, plasmonic sensors with a fast response time can be fabricated with thick, melt-processed nanocomposites, which paves the way for a new generation of robust H₂ sensors.

The role of positive charged residue in the proton-transfer mechanism of two-domain laccase from Streptomyces griseoflavus Ac-993

Multi-copper oxidases are capable of coupling the one-electron oxidation of four substrate equivalents to the four-electron reduction of dioxygen to two molecules of water. This process takes place at the trinuclear copper center of the enzymes. Previously, the main catalytic stages for three-domain (3D) laccases have been identified. However, for bacterial small two-domain (2D) laccases several questions remain to be answered. One of them is the nature of the protonation events upon the reductive cleavage of dioxygen to water. In 3D laccases, acidic residues play a key role in the protonation mechanisms. In this study, the role of the Arg240 residue, located within the T2 tunnel of 2D laccase from Streptomyces griseoflavus Ac-993, was investigated. X-ray structural analysis and kinetic characterization of two mutants, R240A and R240H, have provided support for a role of this residue in the protonation events. Communicated by Ramaswamy H. Sarma.

Tilting and rotational motions of silver halide crystal with diffracted X-ray blinking

The dynamic properties of crystalline materials are important for understanding their local environment or individual single-grain motions. A new time-resolved observation method is required for use in many fields of investigation. Here, we developed in situ diffracted X-ray blinking to monitor high-resolution diffraction patterns from single-crystal grains with a 50 ms time resolution. The diffraction spots of single grains of silver halides and silver moved in the θ and χ directions during the photolysis chemical reaction. The movements of the spots represent tilting and rotational motions. The time trajectory of the diffraction intensity reflecting those motions was analysed by using single-pixel autocorrelation function (sp-ACF). Single-pixel ACF analysis revealed significant differences in the distributions of the ACF decay constants between silver halides, suggesting that the motions of single grains are different between them. The rotational diffusion coefficients for silver halides were estimated to be accurate at the level of approximately 0.1 to 0.3 pm²/s. Furthermore, newly formed silver grains on silver halides correlated with their ACF decay constants. Our high-resolution atomic scale measurement—sp-ACF analysis of diffraction patterns of individual grains—is useful for evaluating physical properties that are broadly applicable in physics, chemistry, and materials science.

Characterization and performance evaluation of the XSPA-500k detector using synchrotron radiation

Hybrid photon counting (HPC) detectors are widely used at both synchrotron facilities and in-house laboratories. The features of HPC detectors, such as no readout noise, high dynamic range, high frame rate, excellent point spread function, no blurring etc. along with fast data acquisition, provide a high-performance detector with a low detection limit and high sensitivity. Several HPC detector systems have been developed around the world. A number of them are commercially available and used in academia and industry. One of the important features of an HPC detector is a fast readout speed. Most HPC detectors can easily achieve over 1000 frames s-1, one or two orders of magnitude faster than conventional CCD detectors. Nevertheless, advanced scientific challenges require ever faster detectors in order to study dynamical phenomena in matter. The XSPA-500k detector can achieve 56 kframes s-1 continuously, without dead-time between frames. Using `burst mode', a special mode of the UFXC32k ASIC, the frame rate reaches 1 000 000 frames s-1. XSPA-500k was fully evaluated at the Metrology beamline at Synchrotron SOLEIL (France) and its readout speed was confirmed by tracking the synchrotron bunch time structure. The uniformity of response, modulation transfer function, linearity, energy resolution and other performance metrics were also verified either with fluorescence X-rays illuminating the full area of the detector or with the direct beam.

In Situ Visualization of the Structural Evolution and Alignment of Lyotropic Liquid Crystals in Confined Flow

Self-assembled materials such as lyotropic liquid crystals offer a wide variety of structures and applications by tuning the composition. Understanding materials behavior under flow and the induced alignment is wanted in order to tailor structure related properties. A method to visualize the structure and anisotropy of ordered systems in situ under dynamic conditions is presented where flow-induced nanostructural alignment in microfluidic channels is observed by scanning small angle X-ray scattering in hexagonal and lamellar self-assembled phases. In the hexagonal phase, the material in regions with high extensional flow exhibits orientation perpendicular to the flow and is oriented in the flow direction only in regions with a high enough shear rate. For the lamellar phase, a flow-induced morphological transition occurs from aligned lamellae toward multilamellar vesicles. However, the vesicles do not withstand the mechanical forces and break in extended lamellae in regions with high shear rates. This evolution of nanostructure with different shear rates can be correlated with a shear thinning viscosity curve with different slopes. The results demonstrate new fundamental knowledge about the structuring of liquid crystals under flow. The methodology widens the quantitative investigation of complex structures and identifies important mechanisms of reorientation and structural changes.

2-Chloro-3-nitro-5-(tri-fluoro-meth-yl)benzoic acid and -benzamide: structural characterization of two precursors for anti-tubercular benzo-thia-zinones

8-Nitro-1,3-benzo-thia-zin-4-ones are a promising class of new anti-tubercular agents, two candidates of which, namely BTZ043 and PBTZ169 (INN: macozinone), have reached clinical trials. The crystal and mol-ecular structures of two synthetic precursors, 2-chloro-3-nitro-5-(tri-fluoro-meth-yl)benzoic acid, C8H3ClF3NO4 (1), and 2-chloro-3-nitro-5-(tri-fluoro-meth-yl)benzamide, C8H4ClF3N2O3 (2), are reported. In 1 and 2, the respective carb-oxy, carboxamide and the nitro groups are significantly twisted out of the plane of the benzene ring. In 1, the nitro group is oriented almost perpendicular to the benzene ring plane. In the crystal, 1 and 2 form O-H⋯O and N-H⋯O hydrogen-bonded dimers, respectively, which in 2 extend into primary amide tapes along the [101] direction. The tri-fluoro-methyl group in 2 exhibits rotational disorder with an occupancy ratio of 0.876 (3):0.124 (3).

Multi-energy calibration of a PILATUS3 CdTe detector for hard x-ray measurements of magnetically confined fusion plasmas

A multi-energy hard x-ray pin-hole camera based on the PILATUS3 X 100K-M CdTe detector has been developed at the Princeton Plasma Physics Laboratory for installation on the Tungsten Environment in Steady State Tokamak. This camera will be employed to study thermal plasma features such as electron temperature as well as non-thermal effects such as fast electron tails produced by a lower hybrid radiofrequency current drive and the birth of runaway electrons. The innovative aspect of the system lies in the possibility of setting the threshold energy independently for each of the ∼100k pixels of the detector. This feature allows for the measurement of the x-ray emission in multiple energy ranges with adequate space and time resolution (∼1 cm, 2 ms) and coarse energy resolution. In this work, the energy dependence of each pixel was calibrated within the range 15 keV-100 keV using a tungsten x-ray tube and emission from a variety of fluorescence targets (from yttrium to uranium). The data corresponding to pairs of K_α emission lines are fit to the characteristic responsivity ("S-curve"), which describes the detector sensitivity across the 64 possible energy threshold values for each pixel; this novel capability is explored by fine-tuning the voltage of a six-bit digital-analog converter after the charge-sensitive amplifier for each of the ∼100k pixels. This work presents the results of the calibration including a statistical analysis. It was found that the achievable energy resolution is mainly limited by the width of the S-curve to 3 keV-10 keV for threshold energies up to 50 keV, and to ≥20 keV for energies above 60 keV.

Kilohertz Macromolecular Crystallography Using an EIGER Detector at Low X-ray Fluxes

Time-resolved in-house macromolecular crystallography is primarily limited by the capabilities of the in-house X-ray sources. These sources can only provide a time-averaged structure of the macromolecules. A significant effort has been made in the development of in-house laser-driven ultrafast X-ray sources, with one of the goals as realizing the visualization of the structural dynamics of macromolecules at a very short timescale within the laboratory-scale infrastructure. Most of such in-house ultrafast X-ray sources are operated at high repetition rates and usually deliver very low flux. Therefore, the necessity of a detector that can operate at the repetition rate of the laser and perform extremely well under low flux conditions is essential. Here, we present experimental results demonstrating the usability of the hybrid-pixel detectors, such as Eiger X 1M, and provide experimental proof that they can be successfully operated to collect macromolecular crystallographic data up to a detector frame rate of 3 kHz from synchrotron sources. Our results also show that the data reduction and structural analysis are successful at such high frame rates and fluxes as low as 108 photons/s, which is comparable to the values expected from a typical laser-driven X-ray source.

Comparison of small-angle neutron and X-ray scattering for studying cortical bone nanostructure

In this study, we present a combined small-angle neutron and X-ray scattering (SANS and SAXS) study of the nanoscale structure of cortical bone specimens from three different species. The variation of the scattering cross section of elements across the periodic table is very different for neutrons and X-rays. For X-rays, it is proportional to the electron density while for neutrons it varies irregularly with the atomic number. Hence, combining the two techniques on the same specimens allows for a more detailed interpretation of the scattering patterns as compared to a single-contrast experiment. The current study was performed on bovine, porcine and ovine specimens, obtained in two perpendicular directions with respect to the main axis of the bone (longitudinal and radial) in order to maximise the understanding of the nanostructural organisation. The specimens were also imaged with high resolution micro-computed tomography (micro-CT), yielding tissue mineral density and microstructural orientation as reference. We show that the SANS and SAXS patterns from the same specimen are effectively identical, suggesting that these bone specimens can be approximated as a two-component composite material. Hence, the observed small-angle scattering results mainly from the mineral-collagen contrast, apart from minor features associated with the internal collagen structure.

Small-angle X-ray scattering experiments of monodisperse intrinsically disordered protein samples close to the solubility limit

The condensation of biomolecules into biomolecular condensates via liquid-liquid phase separation (LLPS) is a ubiquitous mechanism that drives cellular organization. To enable these functions, biomolecules have evolved to drive LLPS and facilitate partitioning into biomolecular condensates. Determining the molecular features of proteins that encode LLPS will provide critical insights into a plethora of biological processes. Problematically, probing biomolecular dense phases directly is often technologically difficult or impossible. By capitalizing on the symmetry between the conformational behavior of biomolecules in dilute solution and dense phases, it is possible to infer details critical to phase separation by precise measurements of the dilute phase thus circumventing complicated characterization of dense phases. The symmetry between dilute and dense phases is found in the size and shape of the conformational ensemble of a biomolecule-parameters that small-angle X-ray scattering (SAXS) is ideally suited to probe. Recent technological advances have made it possible to accurately characterize samples of intrinsically disordered protein regions at low enough concentration to avoid interference from intermolecular attraction, oligomerization or aggregation, all of which were previously roadblocks to characterizing self-assembling proteins. Herein, we describe the pitfalls inherent to measuring such samples, the experimental details required for circumventing these issues and analysis methods that place the results of SAXS measurements into the theoretical framework of LLPS.

Particle Size Distribution of Bimodal Silica Nanoparticles: A Comparison of Different Measurement Techniques

Silica nanoparticles (SNPs) belong to the most widely produced nanomaterials nowadays. Particle size distribution (PSD) is a key property of SNPs that needs to be accurately determined for a successful application. Many single particle and ensemble characterization methods are available for the determination of the PSD of SNPs, each having different advantages and limitations. Since most preparation protocols for SNPs can yield bimodal or heterogeneous PSDs, the capability of a given method to resolve bimodal PSD is of great importance. In this work, four different methods, namely transmission electron microscopy (TEM), dynamic light scattering (DLS), microfluidic resistive pulse sensing (MRPS) and small-angle X-ray scattering (SAXS) were used to characterize three different, inherently bimodal SNP samples. We found that DLS is unsuitable to resolve bimodal PSDs, while MRPS has proven to be an accurate single-particle size and concentration characterization method, although it is limited to sizes above 50 nm. SAXS was found to be the only method which provided statistically significant description of the bimodal PSDs. However, the analysis of SAXS curves becomes an ill-posed inverse mathematical problem for broad size distributions, therefore the use of orthogonal techniques is required for the reliable description of the PSD of SNPs.

Structure of the ribosomal P stalk base in archaean Methanococcus jannaschii

Complexes of archaeal ribosomal proteins uL11 and uL10/P0 (the two-domain N-terminal fragment of uL10, uL10NTF/P0NTF) with the adjacent 74 nucleotides of 23S rRNA fragment (23SrRNA(74)) from Methanococcus jannaschii (Mja) were obtained, crystallized and their structures were studied. The comparative structural analysis of the complexes of Mja uL10NTF•23SrRNA(74) and Mja uL10NTF•uL11•23SrRNA(74) shows that the insertion of uL11 in the binary complex does not change the conformation of the 23S rRNA fragment. On the other hand, the interaction with this specific RNA fragment leads to the restructuring of uL11 compared to the structure of this protein in the free state. Besides, although analysis confirmed the mobility of uL10/P0 domain II, disproved the assumption that it may be in contact with rRNA or uL11. In addition, the Mja uL10NTF•uL11•23SrRNA(74) complex was cocrystallized with the antibiotic thiostrepton, and the structure of this complex was solved. The thiostrepton binding site in this archaeal complex was found between the 23S rRNA and the N-terminal domain (NTD) of the Mja uL11 protein, similar to its binding site in the one of bacterial ribosome complex with thiostrepton. Upon binding of thiostrepton, the NTD of uL11 shifts toward rRNA by 7 Å. Such a shift may be the cause of the inhibitory effect of the antibiotic on the recruitment of translation factors to the GTPase-activating region in archaeal ribosomes, similar to its inhibitory effect on protein synthesis in bacterial ribosomes.

Accurate high-resolution single-crystal diffraction data from a Pilatus3 X CdTe detector

Hybrid photon-counting detectors are widely established at third-generation synchrotron facilities and the specifications of the Pilatus3 X CdTe were quickly recognized as highly promising in charge-density investigations. This is mainly attributable to the detection efficiency in the high-energy X-ray regime, in combination with a dynamic range and noise level that should overcome the perpetual problem of detecting strong and weak data simultaneously. These benefits, however, come at the expense of a persistent problem for high diffracted beam flux, which is particularly problematic in single-crystal diffraction of materials with strong scattering power and sharp diffraction peaks. Here, an in-depth examination of data collected on an inorganic material, FeSb2, and an organic semiconductor, rubrene, revealed systematic differences in strong intensities for different incoming beam fluxes, and the implemented detector intensity corrections were found to be inadequate. Only significant beam attenuation for the collection of strong reflections was able to circumvent this systematic error. All data were collected on a bending-magnet beamline at a third-generation synchrotron radiation facility, so undulator and wiggler beamlines and fourth-generation synchrotrons will be even more prone to this error. On the other hand, the low background now allows for an accurate measurement of very weak intensities, and it is shown that it is possible to extract structure factors of exceptional quality using standard crystallographic software for data processing (SAINT-Plus, SADABS and SORTAV), although special attention has to be paid to the estimation of the background. This study resulted in electron-density models of substantially higher accuracy and precision compared with a previous investigation, thus for the first time fulfilling the promise of photon-counting detectors for very accurate structure factor measurements.

Revealing the Microscopic Structure of Human Renal Cell Carcinoma in Three Dimensions

For fully characterizing renal cell carcinoma (RCC), information about the 3D tissue microstructure is essential. Histopathology, which represents the current diagnostic gold standard, is destructive and only provides 2D information. 3D X-ray histology endeavors to overcome these limitations by generating 3D data. In a laboratory environment, most techniques struggle with limited resolution and the weak X-ray attenuation contrast of soft tissue. We recently developed a laboratory-based method combining nanoscopic X-ray CT with a cytoplasm-specific X-ray stain. Here, we present the application of this method to human RCC biopsies. The NanoCT slices enable pathological characterization of crucial structures by reproducing tissue morphology with a similar detail level as corresponding histological light microscopy images. Beyond that, our data offer deeper insights into the 3D configuration of the tumor. By demonstrating the compatibility of the X-ray stain with standard pathological stains, we highlight the feasibility of integrating staining based NanoCT into the pathological routine.

Validation study of small-angle X-ray scattering tensor tomography

Small-angle scattering tensor tomography (SASTT) is a recently developed technique able to tomographically reconstruct the 3D reciprocal space from voxels within a bulk volume. SASTT extends the concept of X-ray computed tomography, which typically reconstructs scalar values, by reconstructing a tensor per voxel, which represents the local nanostructure 3D organization. In this study, the nanostructure orientation in a human trabecular-bone sample obtained by SASTT was validated by sectioning the sample and using 3D scanning small-angle X-ray scattering (3D sSAXS) to measure and analyze the orientation from single voxels within each thin section. Besides the presence of cutting artefacts from the slicing process, the nanostructure orientations obtained with the two independent methods were in good agreement, as quantified with the absolute value of the dot product calculated between the nanostructure main orientations obtained in each voxel. The average dot product per voxel over the full sample containing over 10 000 voxels was 0.84, and in six slices, in which fewer cutting artefacts were observed, the dot product increased to 0.91. In addition, SAXS tensor tomography not only yields orientation information but can also reconstruct the full 3D reciprocal-space map. It is shown that the measured anisotropic scattering for individual voxels was reproduced from the SASTT reconstruction in each voxel of the 3D sample. The scattering curves along different 3D directions are validated with data from single voxels, demonstrating SASTT's potential for a separate analysis of nanostructure orientation and structural information from the angle-dependent intensity distribution.

Nanoscopic X-ray tomography for correlative microscopy of a small meiofaunal sea-cucumber

In the field of correlative microscopy, light and electron microscopy form a powerful combination for morphological analyses in zoology. Due to sample thickness limitations, these imaging techniques often require sectioning to investigate small animals and thereby suffer from various artefacts. A recently introduced nanoscopic X-ray computed tomography (NanoCT) setup has been used to image several biological objects, none that were, however, embedded into resin, which is prerequisite for a multitude of correlative applications. In this study, we assess the value of this NanoCT for correlative microscopy. For this purpose, we imaged a resin-embedded, meiofaunal sea cucumber with an approximate length of 1 mm, where microCT would yield only little information about the internal anatomy. The resulting NanoCT data exhibits isotropic 3D resolution, offers deeper insights into the 3D microstructure, and thereby allows for a complete morphological characterization. For comparative purposes, the specimen was sectioned subsequently to evaluate the NanoCT data versus serial sectioning light microscopy (ss-LM). To correct for mechanical instabilities and drift artefacts, we applied an alternative alignment procedure for CT reconstruction. We thereby achieve a level of detail on the subcellular scale comparable to ss-LM images in the sectioning plane.

Structural Modeling Using Solution Small-Angle X-ray Scattering (SAXS)

Small-angle X-ray scattering (SAXS) offers a way to examine the overall shape and oligomerization state of biological macromolecules under quasi native conditions in solution. In the past decades, SAXS has become a standard tool for structure biologists due to the availability of high brilliance X-ray sources and the development of data analysis/interpretation methods. Sample handling robots and software pipelines have significantly reduced the time necessary to conduct SAXS experiments. Presently, most synchrotrons feature beamlines dedicated to biological SAXS, and the SAXS-derived models are deposited into dedicated and accessible databases. The size of macromolecules that may be analyzed ranges from small peptides or snippets of nucleic acids to gigadalton large complexes or even entire viruses. Compared to other structural methods, sample preparation is straightforward, and the risk of inducing preparation artefacts is minimal. Very importantly, SAXS is a method of choice to study flexible systems like unfolded or disordered proteins, providing the structural ensembles compatible with the data. Although it may be utilized stand-alone, SAXS profits a lot from available experimental or predicted high-resolution data and information from complementary biophysical methods. Here, we show the basic principles of SAXS and review latest developments in the fields of hybrid modeling and flexible systems.

Vacuum-compatible photon-counting hybrid pixel detector for wide-angle x-ray scattering, x-ray diffraction, and x-ray reflectometry in the tender x-ray range

A vacuum-compatible photon-counting hybrid pixel detector has been installed in the ultra-high vacuum reflectometer of the four-crystal monochromator beamline of the Physikalisch-Technische Bundesanstalt at the electron storage ring BESSY II in Berlin, Germany. The setup is based on the PILATUS3 100K module. The detector can be used in the entire photon energy range accessible at the beamline from 1.75 keV to 10 keV. Complementing the already installed vacuum-compatible PILATUS 1M detector used for small-angle x-ray scattering (SAXS) and grazing incidence SAXS, it is possible to access larger scattering angles. The water-cooled module is located on the goniometer arm and can be positioned from -90° to 90° with respect to the incoming beam at a distance of about 200 mm from the sample. To perform absolute scattering experiments, the linearity, homogeneity, and angular dependence of the quantum efficiency, including their relative uncertainties, have been investigated. In addition, the first results of the performance in wide-angle x-ray scattering, x-ray diffraction, and x-ray reflectometry are presented.

Single crystal growth of water-soluble metal complexes with the help of the nano-crystallization method

Let pipetting robots set up nano crystallization trials of water-soluble metal complexes in order to obtain single crystals!

Picosecond pump-probe X-ray scattering at the Elettra SAXS beamline

A new setup for picosecond pump-probe X-ray scattering at the Austrian SAXS beamline at Elettra-Sincrotrone Trieste is presented. A high-power/high-repetion-rate laser has been installed on-site, delivering UV/VIS/IR femtosecond-pulses in-sync with the storage ring. Data acquisition is achieved by gating a multi-panel detector, capable of discriminating the single X-ray pulse in the dark-gap of the Elettra hybrid filling mode. Specific aspects of laser- and detection-synchronization, on-line beam steering as well protocols for spatial and temporal overlap of laser and X-ray beam are also described. The capabilities of the setup are demonstrated by studying transient heat-transfer in an In/Al/GaAs superlattice structure and results are confirmed by theoretical calculations.

DIY XES - development of an inexpensive, versatile, and easy to fabricate XES analyzer and sample delivery system

The application of X-ray emission spectroscopy (XES) has grown substantially with the development of X-ray free electron lasers, third and fourth generation synchrotron sources and high-power benchtop sources. By providing the high X-ray flux required for XES, these sources broaden the availability and application of this method of probing electronic structure. As the number of sources increase, so does the demand for X-ray emission detection and sample delivery systems that are cost effective and customizable. Here, we present a detailed fabrication protocol for von Hamos X-ray optics and give details for a 3D-printed spectrometer design. Additionally, we outline an automated, externally triggered liquid sample delivery system that can be used to repeatedly deliver nanoliter droplets onto a plastic substrate for measurement. These systems are both low cost, efficient and easy to recreate or modify depending on the application. A low cost multiple X-ray analyzer system enables measurement of dilute samples, whereas the sample delivery limits sample loss and replaces spent sample with fresh sample in the same position. While both systems can be used in a wide range of applications, the design addresses several challenges associated specifically with time-resolved XES (TRXES). As an example application, we show results from TRXES measurements of photosystem II, a dilute, photoactive protein.

Energy-dispersive Laue diffraction by means of a pnCCD detector coupled to a CsI(Tl) scintillator using ultra-hard X-ray synchrotron radiation

The lattice parameters and unit-cell orientation of an SrLaAlO₄ crystal have been determined by means of energy-dispersive X-ray Laue diffraction (EDLD) using a pnCCD detector coupled to a columnar structure CsI(Tl) scintillator in the energy range between 40 and 130 keV. By exploiting the high quantum efficiency (QE) achieved by this combined detection system for hard X-rays, a large number of Bragg reflections could be recorded by the relatively small detector area, allowing accurate and fast determination of the lattice parameters and the moduli of the structure factors. The experiment was performed on the energy-dispersive diffraction (EDDI) beamline at the BESSY II synchrotron using a pnCCD detector with 128 × 128 pixels. Since the energies and positions of the Laue peaks can be recorded simultaneously by the pnCCD system, the tetragonal structure of the investigated specimen was determined without any prior information. The unit-cell parameters and the angles between the lattice vectors were evaluated with an accuracy of better than 0.7%, while the structure-factor moduli of the reflections were determined with a mean deviation of 2.5% relative to the theoretical values.

Development of low-energy X-ray detectors using LGAD sensors

Recent advances in segmented low-gain avalanche detectors (LGADs) make them promising for the position-sensitive detection of low-energy X-ray photons thanks to their internal gain. LGAD microstrip sensors fabricated by Fondazione Bruno Kessler have been investigated using X-rays with both charge-integrating and single-photon-counting readout chips developed at the Paul Scherrer Institut. In this work it is shown that the charge multiplication occurring in the sensor allows the detection of X-rays with improved signal-to-noise ratio in comparison with standard silicon sensors. The application in the tender X-ray energy range is demonstrated by the detection of the sulfur K_α and K_β lines (2.3 and 2.46 keV) in an energy-dispersive fluorescence spectrometer at the Swiss Light Source. Although further improvements in the segmentation and in the quantum efficiency at low energy are still necessary, this work paves the way for the development of single-photon-counting detectors in the soft X-ray energy range.