I thought it would be fun to document the smallest possible valid HTML documents for each version, so here goes :)

Researchers develop an MS shotgun proteomic method to tackle small numbers of cancer cells in blood.

Shriya Saran urges fans to help small businesses during the COVID-19 crisis

Possibilities in auxiliary technique combinations with small- and wide-angle X ray scattering are described, as well as more complicated sample environments used in X-ray and neutron scattering.

A review of recent and ongoing development and results within the field of biological solution small-angle X-ray scattering (BioSAXS), with a focus on the increasing complexity of biological samples, data collection and data evaluation strategies.

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Protein–protein and protein–ligand interactions often involve conformational changes or structural rearrangements that can be quantified by solution small-angle X-ray scattering (SAXS). These scattering intensity measurements reveal structural details of the bound complex, the number of species involved and, additionally, the strength of interactions if carried out as a titration. Although a core part of structural biology workflows, SAXS-based titrations are not commonly used in drug discovery contexts. This is because prior knowledge of expected sample requirements, throughput and prediction accuracy is needed to develop reliable ligand screens. This study presents the use of the histidine-binding protein (26 kDa) and other periplasmic binding proteins to benchmark ligand screen performance. Sample concentrations and exposure times were varied across multiple screening trials at four beamlines to investigate the accuracy and precision of affinity prediction. The volatility ratio between titrated scattering curves and a common apo reference is found to most reliably capture the extent of structural and population changes. This obviates the need to explicitly model scattering intensities of bound complexes, which can be strongly ligand-dependent. Where the dissociation constant is within 102 of the protein concentration and the total exposure times exceed 20 s, the titration protocol presented at 0.5 mg ml−1 yields affinities comparable to isothermal titration calorimetry measurements. Estimated throughput ranges between 20 and 100 ligand titrations per day at current synchrotron beamlines, with the limiting step imposed by sample handling and cleaning procedures.

The crystal structure of the c-type cytochrome NirC from Pseudomonas aeruginosa has been determined and reveals the simultaneous presence of monomers and 3D domain-swapped dimers in the same asymmetric unit.

Instrumentation for time-resolved small-angle neutron scattering measurements with sub-millisecond time resolution, based on Gähler's TISANE (time-involved small-angle neutron experiments) concept, is in operation at NIST's Center for Neutron Research. This implementation of the technique includes novel electronics for synchronizing the neutron pulses from high-speed counter-rotating choppers with a periodic stimulus applied to a sample. Instrumentation details are described along with measurements demonstrating the utility of the technique for elucidating the reorientation dynamics of anisometric magnetic particles.

Traditionally small-molecule crystallographers have not usually observed or recognized significant radiation damage to their samples during diffraction experiments. However, the increased flux densities provided by third-generation synchrotrons have resulted in increasing numbers of observations of this phenomenon. The diversity of types of small-molecule systems means it is not yet possible to propose a general mechanism for their radiation-induced sample decay, however characterization of the effects will permit attempts to understand and mitigate it. Here, systematic experiments are reported on the effects that sample temperature and beam attenuation have on radiation damage progression, allowing qualitative and quantitative assessment of their impact on crystals of a small-molecule test sample. To allow inter-comparison of different measurements, radiation-damage metrics (diffraction-intensity decline, resolution fall-off, scaling B-factor increase) are plotted against the absorbed dose. For ease-of-dose calculations, the software developed for protein crystallography, RADDOSE-3D, has been modified for use in small-molecule crystallography. It is intended that these initial experiments will assist in establishing protocols for small-molecule crystallographers to optimize the diffraction signal from their samples prior to the onset of the deleterious effects of radiation damage.

As is well known, polymers commonly form lamellar crystals, and these assemble further into lamellar stacks and spherulites during quiescent crystallization. Fifty years ago, Vonk and Kortleve constructed the classical small-angle X-ray scattering theory (SAXS) for a lamellar system, in which it was assumed that the lamellar stack had an infinite lateral size [Vonk & Kortleve (1967), Kolloid Z. Z. Polym. 220, 19–24]. Under this assumption, only crystal planes satisfying the Bragg condition can form strong scattering, and the scattering from the lamellar stack arises from the difference between the scattering intensities in the amorphous and crystalline layers, induced by the incident X-ray beam. This assumption is now deemed unreasonable. In a real polymer spherulite, the lamellar crystal commonly has dimensions of only a few hundred nanometres. At such a limited lateral size, lamellar stacks in a broad orientation have similar scattering, so interference between these lamellar stacks must be considered. Scattering from lamellar stacks parallel to the incident X-ray beam also needs to be considered when total reflection occurs. In this study, various scattering contributions from lamellar stacks in a spherulite are determined. It is found that, for a limited lateral size, the scattering induced by the incident X-ray beam is not the main origin of SAXS. It forms double peaks, which are not observed in real scattering because of destructive interference between the lamellar stacks. The scattering induced by the evanescent wave is the main origin. It can form a similar interference pattern to that observed in a real SAXS measurement: a Guinier region in the small-q range, a signal region in the intermediate-q range and a Porod region in the high-q range. It is estimated that, to avoid destructive interference, the lateral size needs to be greater than 11 µm, which cannot be satisfied in a real lamellar system. Therefore, SAXS in a real polymer system arises largely from the scattering induced by the evanescent wave. Evidence for the existence of the evanescent wave was identified in the scattering of isotactic polypropyl­ene. This study corrects a long-term misunderstanding of SAXS in a polymer lamellar system.

Small-angle neutron scattering (SANS) is one of the most widely used neutron-based approaches to study the solution structure of biological macromolecular systems. The selective deuterium labelling of different protein components of a complex provides a means to probe conformational changes in multiprotein complexes. The Lysinibacillus sphaericus mosquito-larvicidal BinAB proteins exert toxicity through interaction with the receptor Cqm1 protein; however, the nature of the complex is not known. Rationally engineered deuterated BinB (dBinB) protein from the L. sphaericus ISPC-8 species was synthesized using an Escherichia coli-based protein-expression system in M9 medium in D2O for `contrast-matched' SANS experiments. SANS data were independently analysed by ab initio indirect Fourier transform-based modelling and using crystal structures. These studies confirm the dimeric status of Cqm1 in 100% D2O with a longest intramolecular vector (Dmax) of ∼94 Å and a radius of gyration (Rg) of ∼31 Å. Notably, BinB binds to Cqm1, forming a heterodimeric complex (Dmax of ∼129 Å and Rg of ∼40 Å) and alters its oligomeric status from a dimer to a monomer, as confirmed by matched-out Cqm1–dBinB (Dmax of ∼70 Å and Rg of ∼22 Å). The present study thus provides the first insight into the events involved in the internalization of larvicidal proteins, likely by raft-dependent endocytosis.

Innovative new crystallographic methods are facilitating structural studies from ever smaller crystals of biological macromolecules. In particular, serial X-ray crystallography and microcrystal electron diffraction (MicroED) have emerged as useful methods for obtaining structural information from crystals on the nanometre to micrometre scale. Despite the utility of these methods, their implementation can often be difficult, as they present many challenges that are not encountered in traditional macromolecular crystallography experiments. Here, XFEL serial crystallography experiments and MicroED experiments using batch-grown microcrystals of the enzyme cyclophilin A are described. The results provide a roadmap for researchers hoping to design macromolecular microcrystallography experiments, and they highlight the strengths and weaknesses of the two methods. Specifically, we focus on how the different physical conditions imposed by the sample-preparation and delivery methods required for each type of experiment affect the crystal structure of the enzyme.

Monoheme c-type cytochromes are important electron transporters in all domains of life. They possess a common fold hallmarked by three α-helices that surround a covalently attached heme. An intriguing feature of many monoheme c-type cytochromes is their capacity to form oligomers by exchanging at least one of their α-helices, which is often referred to as 3D domain swapping. Here, the crystal structure of NirC, a c-type cytochrome co-encoded with other proteins involved in nitrite reduction by the opportunistic pathogen Pseudomonas aeruginosa, has been determined. The crystals diffracted anisotropically to a maximum resolution of 2.12 Å (spherical resolution of 2.83 Å) and initial phases were obtained by Fe-SAD phasing, revealing the presence of 11 NirC chains in the asymmetric unit. Surprisingly, these protomers arrange into one monomer and two different types of 3D domain-swapped dimers, one of which shows pronounced asymmetry. While the simultaneous observation of monomers and dimers probably reflects the interplay between the high protein concentration required for crystallization and the structural plasticity of monoheme c-type cytochromes, the identification of conserved structural motifs in the monomer together with a comparison with similar proteins may offer new leads to unravel the unknown function of NirC.

ID30A-3 (or MASSIF-3) is a mini-focus (beam size 18 µm × 14 µm) highly intense (2.0 × 1013 photons s−1), fixed-energy (12.81 keV) beamline for macromolecular crystallography (MX) experiments at the European Synchrotron Radiation Facility (ESRF). MASSIF-3 is one of two fixed-energy beamlines sited on the first branch of the canted undulator setup on the ESRF ID30 port and is equipped with a MD2 micro-diffractometer, a Flex HCD sample changer, and an Eiger X 4M fast hybrid photon-counting detector. MASSIF-3 is recommended for collecting diffraction data from single small crystals (≤15 µm in one dimension) or for experiments using serial methods. The end-station has been in full user operation since December 2014, and here its current characteristics and capabilities are described.

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.

Convolutional neural networks are useful for classifying grazing-incidence small-angle X-ray scattering patterns. They are also useful for classifying real experimental data.

The open-source Python program PDB2INS is designed to prepare a .ins file for refinement with SHELXL [Sheldrick (2015). Acta Cryst. C71, 3–8], taking atom coordinates and other information from a Protein Data Bank (PDB)-format file. If PDB2INS is provided with a four-character PDB code, both the PDB file and the accompanying mmCIF-format reflection data file (if available) are accessed via the internet from the PDB public archive [Read et al. (2011). Structure, 19, 1395–1412] or optionally from the PDB_REDO server [Joosten, Long, Murshudov & Perrakis (2014). IUCrJ, 1, 213–220]. The SHELX-format .ins (refinement instructions and atomic coordinates) and .hkl (reflection data) files can then be generated without further user intervention, appropriate restraints etc. being added automatically. PDB2INS was tested on the 23 974 X-ray structures deposited in the PDB between 2008 and 2018 that included reflection data to 1.7 Å or better resolution in a recognizable format. After creating the two input files for SHELXL without user intervention, ten cycles of conjugate-gradient least-squares refinement were performed. For 96% of these structures PDB2INS and SHELXL completed successfully without error messages.

Nanoporous anodic aluminium oxide (AAO) membranes are promising host systems for confinement of condensed matter. Characterizing their structure and composition is thus of primary importance for studying the behavior of confined objects. Here a novel methodology to extract quantitative information on the structure and composition of well defined AAO membranes by combining small-angle neutron scattering (SANS) measurements and scanning electron microscopy (SEM) imaging is reported. In particular, (i) information about the pore hexagonal arrangement is extracted from SEM analysis, (ii) the best SANS experimental conditions to perform reliable measurements are determined and (iii) a detailed fitting method is proposed, in which the probed length in the fitting model is a critical parameter related to the longitudinal pore ordering. Finally, to validate this strategy, it is applied to characterize AAOs prepared under different conditions and it is shown that the experimental SANS data can be fully reproduced by a core/shell model, indicating the existence of a contaminated shell. This original approach, based on a detailed and complete description of the SANS data, can be applied to a variety of confining media and will allow the further investigation of condensed matter under confinement.

Grazing-incidence small-angle X-ray scattering (GISAXS) coupled with computed tomography (CT) has enabled the visualization of the spatial distribution of nanostructures in thin films. 2D GISAXS images are obtained by scanning along the direction perpendicular to the X-ray beam at each rotation angle. Because the intensities at the q positions contain nanostructural information, the reconstructed CT images individually represent the spatial distributions of this information (e.g. size, shape, surface, characteristic length). These images are reconstructed from the intensities acquired at angular intervals over 180°, but the total measurement time is prolonged. This increase in the radiation dosage can cause damage to the sample. One way to reduce the overall measurement time is to perform a scanning GISAXS measurement along the direction perpendicular to the X-ray beam with a limited interval angle. Using filtered back-projection (FBP), CT images are reconstructed from sinograms with limited interval angles from 3 to 48° (FBP-CT images). However, these images are blurred and have a low image quality. In this study, to optimize the CT image quality, total variation (TV) regularization is introduced to minimize sinogram image noise and artifacts. It is proposed that the TV method can be applied to downsampling of sinograms in order to improve the CT images in comparison with the FBP-CT images.

BornAgain is a free and open-source multi-platform software framework for simulating and fitting X-ray and neutron reflectometry, off-specular scattering, and grazing-incidence small-angle scattering (GISAS). This paper concentrates on GISAS. Support for reflectometry and off-specular scattering has been added more recently, is still under intense development and will be described in a later publication. BornAgain supports neutron polarization and magnetic scattering. Users can define sample and instrument models through Python scripting. A large subset of the functionality is also available through a graphical user interface. This paper describes the software in terms of the realized non-functional and functional requirements. The web site https://www.bornagainproject.org/ provides further documentation.

Small-angle neutron scattering (SANS) was recently applied to the in situ and operando study of the charge/discharge process in Li-ion battery full-cells based on a pouch cell design. Here, this work is continued in a half-cell with a graphite electrode cycled versus a metallic lithium counter electrode, in a study conducted on the SANS-1 instrument of the neutron source FRM II at the Heinz Maier-Leibnitz Zentrum in Garching, Germany. It is confirmed that the SANS integrated intensity signal varies as a function of graphite lithiation, and this variation can be explained by changes in the squared difference in scattering length density between graphite and the electrolyte. The scattering contrast change upon graphite lithiation/delithiation calculated from a multi-phase neutron scattering model is in good agreement with the experimentally measured values. Due to the finite coherence length, the observed SANS contrast, which mostly stems from scattering between the (lithiated) graphite and the electrolyte phase, contains local information on the mesoscopic scale, which allows the development of lithiated phases in the graphite to be followed. The shape of the SANS signal curve can be explained by a core–shell model with step-wise (de)lithiation from the surface. Here, for the first time, X-ray diffraction, SANS and theory are combined to give a full picture of graphite lithiation in a half-cell. The goal of this contribution is to confirm the correlation between the integrated SANS data obtained during operando measurements of an Li-ion half-cell and the electrochemical processes of lithiation/delithiation in micro-scaled graphite particles. For a deeper understanding of this correlation, modelling and experimental data for SANS and results from X-ray diffraction were taken into account.

Clays and soils produce strong small-angle X-ray scattering (SAXS) because they contain large numbers of nanoparticles, namely allophane and ferrihydrite. These nanoparticles are amorphous and have approximately spherical shape with a size of around 3–10 nm. The weight ratios of these nanoparticles will affect the properties of the clays and soils. However, the nanoparticles in clays and soils are not generally quantified and are sometimes ignored because there is no standard method to quantify them. This paper describes a method to quantify nanoparticles in clays and soils with SAXS. This is achieved by deriving normalized SAXS intensities from unit weight of the sample, which are not affected by absorption. By integrating the normalized SAXS intensities over the reciprocal space, one obtains a value that is proportional to the weight ratio of the nanoparticles, proportional to the square of the difference of density between the nanoparticles and the liquid surrounding the nanoparticles, and inversely proportional to the density of the nanoparticles. If the density of the nanoparticles is known, the weight ratio of the nanoparticles can be calculated from the SAXS intensities. The density of nanoparticles was estimated from the chemical composition of the sample. Nanoparticles in colloidal silica, silica gels, mixtures of silica gel and α-aluminium oxide, and synthetic clays have been quantified with the integral SAXS method. The results show that the errors of the weight ratios of nanoparticles are around 25% of the weight ratio. It is also shown that some natural clays contain large fractions of nanoparticles; montmorillonite clay from the Mikawa deposit, pyrophillite clay from the Shokozan deposit and kaolinite clay from the Kanpaku deposit contain 25 (7), 10 (2) and 19 (5) wt% nanoparticles, respectively, where errors are shown in parentheses.

This article presents IMSIM, an application to simulate two-dimensional small-angle X-ray scattering patterns and, further, one-dimensional profiles from biological macromolecules in solution. IMSIM implements a statistical approach yielding two-dimensional images in TIFF, CBF or EDF format, which may be readily processed by existing data-analysis pipelines. Intensities and error estimates of one-dimensional patterns obtained from the radial average of the two-dimensional images exhibit the same statistical properties as observed with actual experimental data. With initial input on an absolute scale, [cm−1]/c[mg ml−1], the simulated data frames may also be scaled to absolute scale such that the forward scattering after subtraction of the background is proportional to the molecular weight of the solute. The effects of changes of concentration, exposure time, flux, wavelength, sample–detector distance, detector dimensions, pixel size, and the mask as well as incident beam position can be considered for the simulation. The simulated data may be used in method development, for educational purposes, and also to determine the most suitable beamline setup for a project prior to the application and use of the actual beamtime. IMSIM is available as part of the ATSAS software package (3.0.0) and is freely available for academic use (http://www.embl-hamburg.de/biosaxs/download.html).

By using small-angle neutron scattering (SANS) reinforced by scanning electron microscopy, the fine structure of catalysts for polymer electrolyte fuel cells has been investigated. The experimental data resulting from contrast variation with mixed light and heavy water (H2O/D2O) are well described by a core–shell model with fluctuations in concentration between water and Nafion.

This paper reports on the two-scale fractal structure of chromatin organization in the nucleus of the HeLa cell.

An attempt has been made to combine small-angle scattering of X-rays or neutrons with scanning electron microscopy in reciprocal space, in order to establish a structural analysis method covering a wide range of sizes from micro- to macro-scales.

Instrumentation for sub-millisecond time-resolved small-angle neutron scattering measurements at NIST is described and applied to the reorientation dynamics of elongated hematite nanoparticles.

The sasPDF method, an extension of the atomic pair distribution function (PDF) analysis to the small-angle scattering (SAS) regime, is presented. The method is applied to characterize the structure of nanoparticle assemblies with different levels of structural order.

A portable small-angle X-ray scattering instrument with geometrical dimensions suitable for installation at the D22 instrument was designed and constructed for simultaneous small-angle X-ray and neutron scattering experiments at ILL.

Birds do it. Bees do it. And in a laboratory in northern California, scientists using bumblebees recently figured out the best way to measure it--vertical lift!

The post Laboratory tests reveal precise way to measure vertical lift in bumblebees and other small insects and birds appeared first on Smithsonian Insider.

Bats living in the dense urban area of Panama City, the scientists learned, represent just a small fraction of the roughly 25 species of high-flying insectivorous bats found in Panama’s rainforests.

The post Only large, fast-flying bats can handle life in the big city; small bats can’t adapt appeared first on Smithsonian Insider.

The National Zoo has received a breeding pair of Asian small-clawed otters at Asia Trail for the first time. Mac, a three-year-old male from the Point Defiance Zoo in Tacoma, Wash., and Smidge, a five-year-old female from the Columbus Zoo in Ohio, arrived in April and are now in their exhibit.

The post Keepers are optimistic about Zoo’s new breeding pair of Asian small-clawed otters appeared first on Smithsonian Insider.

Small monkey groups may win territorial disputes against larger groups because some members of the larger, invading groups avoid aggressive encounters.

The post Members of small monkey groups more likely to fight, researchers find appeared first on Smithsonian Insider.

Small migratory male birds that winter in a stressful environment age faster than those that winter in a high-quality habitat, according to research stemming from […]

The post Small migratory birds age faster in stressful places, study reveals appeared first on Smithsonian Insider.

Stars form when gravity pulls together material within giant clouds of gas and dust. But gravity isn’t the only force at work. Both turbulence and […]

The post As Stars Form, Magnetic Fields Influence Regions Big and Small appeared first on Smithsonian Insider.

For the first time, researchers at the Smithsonian Conservation Biology Institute’s Migratory Bird Center have accurately tracked small migratory ovenbirds (Seiurus aurocapilla) to their tropical […]

The post Miniaturized GPS Tags Allow Tracking of Small Songbirds for first time appeared first on Smithsonian Insider.

Kristina Drizyte-Miller, Jing Chen, Hong Cao, Micah B. Schott, and Mark A. McNiven

Epithelial cells such as liver-resident hepatocytes rely heavily on the Rab family of small GTPases to perform membrane trafficking events that dictate cell physiology and metabolism. Not surprisingly, disruption of several Rabs can manifest in metabolic diseases or cancer. Rab32 is expressed in many secretory epithelial cells but its role in cellular metabolism is virtually unknown. In this study, we find that Rab32 associates with lysosomes and regulates proliferation and cell size of Hep3B hepatoma and HeLa cells. Specifically, we identify that Rab32 supports mTORC1 signaling under basal and amino acid stimulated conditions. Consistent with inhibited mTORC1, an increase in nuclear TFEB localization and lysosome biogenesis is also observed in Rab32-depleted cells. Finally, we find that Rab32 interacts with mTOR kinase and that loss of Rab32 reduces the association of mTOR and mTORC1 pathway proteins with lysosomes, suggesting that Rab32 regulates lysosomal mTOR trafficking. In summary, these findings suggest that Rab32 functions as a novel regulator of cellular metabolism through supporting mTORC1 signaling.

The small-whorled pogonia is a plain, endangered orchid that inhabits the hollows of Virginia, and survives only in collaboration with a particular type of fungus […]

The post The small whorled pogonia appeared first on Smithsonian Insider.

Small-Whorled Pogonia: Endangered Orchid on the Edge. The small-whorled pogonia (Isotria medeoloides) is endangered 16 of the 20 states where it still appears, earning it the title "rarest orchid east of the Mississippi."

The post Small-Whorled Pogonia: Endangered Orchid on the Edge appeared first on Smithsonian Insider.

Finding a mouse in your morning coffee might give you an unwelcome jolt, but there’s a strong connection between small mammals, birds and the plantations […]

The post Of mice and macchiato: Bird Friendly coffee gives a paw-up to small mammals as well appeared first on Smithsonian Insider.

This article aims to encourage practitioners, young and seasoned, by enhancing their structure-determination toolboxes with a selection of tips and tricks on recognizing and handling aspects of data collection, structure modelling and refinement, and the interpretation of results.

The development of antiviral strategies requires a clear understanding of the principles that control the protein arrangements in viral shells. Considered here are those capsids that violate the paradigmatic Caspar and Klug (CK) model, and it is shown that the important structural features of such anomalous shells from the Picobirnaviridae, Flaviviridae and Leviviridae families can be revealed by models in the form of spherical icosahedral packings of equivalent rhombic structural units (SUs). These SUs are composed of protein dimers forming the investigated capsids which, as shown here, are based on the rhombic triacontahedron (RT) geometry. How to modify the original CK approach in order to make it compatible with the considered rhombic tessellations of a sphere is also discussed. Analogies between capsids self-assembled from dimers and trimers are demonstrated. This analysis reveals the principles controlling the localization of receptor proteins (which recognize the host cell) on the capsid surface.

In small-molecule single-crystal structure determination, we now have at our disposal an inspiring range of fantastic diffractometers with better, brighter sources, and faster, more sensitive detectors. Faster and more powerful computers provide integrated tools and software with impressive graphical user interfaces. Yet these tools can lead to the temptation not to check the work thoroughly and one can too easily overlook tell-tale signs that something might be amiss in a structure determination; validation with checkCIF is not always revealing. This article aims to encourage practitioners, young and seasoned, by enhancing their structure-determination toolboxes with a selection tips and tricks on recognizing and handling aspects that one should constantly be aware of. Topics include a pitfall when setting up data collections, the usefulness of reciprocal lattice layer images, processing twinned data, tips for disorder modelling and the use of restraints, ensuring hydrogen atoms are added to a model correctly, validation beyond checkCIF, and the derivation and interpretation of the final results.

Kristina Drizyte-Miller
Apr 15, 2020; 0:jcs.236661v1-jcs.236661
Articles

Radon in household water supplies increases peoples overall exposure to the gas, but waterborne radon poses few risks to human health, says a new report by a committee of the National Research Council.

The emergence of inexpensive small unmanned aircraft systems (sUASs) that operate without a human pilot, commonly known as drones, has led to adversarial groups threatening deployed U.S. forces, especially infantry units.