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Have you heard of the Zone diet? Here’s all you need to know




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On Mother’s Day, relive nostalgia with these 3 recipes for dips




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A versatile nanoreactor for complementary in situ X-ray and electron microscopy studies in catalysis and materials science

Two in situ `nanoreactors' for high-resolution imaging of catalysts have been designed and applied at the hard X-ray nanoprobe endstation at beamline P06 of the PETRA III synchrotron radiation source. The reactors house samples supported on commercial MEMS chips, and were applied for complementary hard X-ray ptychography (23 nm spatial resolution) and transmission electron microscopy, with additional X-ray fluorescence measurements. The reactors allow pressures of 100 kPa and temperatures of up to 1573 K, offering a wide range of conditions relevant for catalysis. Ptychographic tomography was demonstrated at limited tilting angles of at least ±35° within the reactors and ±65° on the naked sample holders. Two case studies were selected to demonstrate the functionality of the reactors: (i) annealing of hierarchical nanoporous gold up to 923 K under inert He environment and (ii) acquisition of a ptychographic projection series at ±35° of a hierarchically structured macroporous zeolite sample under ambient conditions. The reactors are shown to be a flexible and modular platform for in situ studies in catalysis and materials science which may be adapted for a range of sample and experiment types, opening new characterization pathways in correlative multimodal in situ analysis of functional materials at work. The cells will presently be made available for all interested users of beamline P06 at PETRA III.




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Linear array detector for online diagnostics of spectral distributions at MHz repetition rates

Free-electron lasers (FELs) based on superconducting accelerator technology and storage ring facilities operate with bunch repetition rates in the MHz range, and the need arises for bunch-by-bunch electron and photon diagnostics. For photon-pulse-resolved measurements of spectral distributions, fast one-dimensional profile monitors are required. The linear array detector KALYPSO (KArlsruhe Linear arraY detector for MHz-rePetition rate SpectrOscopy) has been developed for electron bunch or photon pulse synchronous read-out with frame rates of up to 2.7 MHz. At the FLASH facility at DESY, a current version of KALYPSO with 256 pixels has been installed at a grating spectrometer as online diagnostics to monitor the pulse-resolved spectra of the high-repetition-rate FEL pulses. Application-specific front-end electronics based on MicroTCA standard have been developed for data acquisition and processing. Continuous data read-out with low latency in the microsecond range enables the integration into fast feedback applications. In this paper, pulse-resolved FEL spectra recorded at 1.0 MHz repetition rate for various operation conditions at FLASH are presented, and the first application of an adaptive feedback for accelerator control based on photon beam diagnostics is demonstrated.




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BioStruct-Africa: empowering Africa-based scientists through structural biology knowledge transfer and mentoring – recent advances and future perspectives

Being able to visualize biology at the molecular level is essential for our understanding of the world. A structural biology approach reveals the molecular basis of disease processes and can guide the design of new drugs as well as aid in the optimization of existing medicines. However, due to the lack of a synchrotron light source, adequate infrastructure, skilled persons and incentives for scientists in addition to limited financial support, the majority of countries across the African continent do not conduct structural biology research. Nevertheless, with technological advances such as robotic protein crystallization and remote data collection capabilities offered by many synchrotron light sources, X-ray crystallography is now potentially accessible to Africa-based scientists. This leap in technology led to the establishment in 2017 of BioStruct-Africa, a non-profit organization (Swedish corporate ID: 802509-6689) whose core aim is capacity building for African students and researchers in the field of structural biology with a focus on prevalent diseases in the African continent. The team is mainly composed of, but not limited to, a group of structural biologists from the African diaspora. The members of BioStruct-Africa have taken up the mantle to serve as a catalyst in order to facilitate the information and technology transfer to those with the greatest desire and need within Africa. BioStruct-Africa achieves this by organizing workshops onsite at our partner universities and institutions based in Africa, followed by post-hoc online mentoring of participants to ensure sustainable capacity building. The workshops provide a theoretical background on protein crystallography, hands-on practical experience in protein crystallization, crystal harvesting and cryo-cooling, live remote data collection on a synchrotron beamline, but most importantly the links to drive further collaboration through research. Capacity building for Africa-based researchers in structural biology is crucial to win the fight against the neglected tropical diseases, e.g. ascariasis, hookworm, trichuriasis, lymphatic filariasis, active trachoma, loiasis, yellow fever, leprosy, rabies, sleeping sickness, onchocerciasis, schistosomiasis, etc., that constitute significant health, social and economic burdens to the continent. BioStruct-Africa aims to build local and national expertise that will have direct benefits for healthcare within the continent.




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Coherent Bragg imaging of 60 nm Au nanoparticles under electrochemical control at the NanoMAX beamline

Nanoparticles are essential electrocatalysts in chemical production, water treatment and energy conversion, but engineering efficient and specific catalysts requires understanding complex structure–reactivity relations. Recent experiments have shown that Bragg coherent diffraction imaging might be a powerful tool in this regard. The technique provides three-dimensional lattice strain fields from which surface reactivity maps can be inferred. However, all experiments published so far have investigated particles an order of magnitude larger than those used in practical applications. Studying smaller particles quickly becomes demanding as the diffracted intensity falls. Here, in situ nanodiffraction data from 60 nm Au nanoparticles under electrochemical control collected at the hard X-ray nanoprobe beamline of MAX IV, NanoMAX, are presented. Two-dimensional image reconstructions of these particles are produced, and it is estimated that NanoMAX, which is now open for general users, has the requisites for three-dimensional imaging of particles of a size relevant for catalytic applications. This represents the first demonstration of coherent X-ray diffraction experiments performed at a diffraction-limited storage ring, and illustrates the importance of these new sources for experiments where coherence properties become crucial.




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Performance of nearly fixed offset asymmetric channel-cut crystals for X-ray monochromators

X-ray double-crystal monochromators face a shift of the exit beam when the Bragg angle and thus the transmitted photon energy changes. This can be compensated for by moving one or both crystals accordingly. In the case of monolithic channel-cut crystals, which exhibit utmost stability, the shift of the monochromated beam is inevitable. Here we report performance tests of novel, asymmetrically cut, channel-cut crystals which reduce the beam movements by more than a factor of 20 relative to the symmetric case over the typical energy range of an EXAFS spectrum at the Cu K-edge. In addition, the presented formulas for the beam offset including the asymmetry angle directly indicate the importance of this value, which has been commonly neglected so far in the operation of double-crystal monochromators.




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X-ray fluorescence analysis of metal distributions in cryogenic biological samples using large-acceptance-angle SDD detection and continuous scanning at the Hard X-ray Micro/Nano-Probe beamline P06 at PETRA III

A new Rococo 2 X-ray fluorescence detector was implemented into the cryogenic sample environment at the Hard X-ray Micro/Nano-Probe beamline P06 at PETRA III, DESY, Hamburg, Germany. A four sensor-field cloverleaf design is optimized for the investigation of planar samples and operates in a backscattering geometry resulting in a large solid angle of up to 1.1 steradian. The detector, coupled with the Xspress 3 pulse processor, enables measurements at high count rates of up to 106 counts per second per sensor. The measured energy resolution of ∼129 eV (Mn Kα at 10000 counts s−1) is only minimally impaired at the highest count rates. The resulting high detection sensitivity allows for an accurate determination of trace element distributions such as in thin frozen hydrated biological specimens. First proof-of-principle measurements using continuous-movement 2D scans of frozen hydrated HeLa cells as a model system are reported to demonstrate the potential of the new detection system.




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Full-field spectroscopic measurement of the X-ray beam from a multilayer monochromator using a hyperspectral X-ray camera

Multilayer monochromator devices are commonly used at (imaging) beamlines of synchrotron facilities to shape the X-ray beam to relatively small bandwidth and high intensity. However, stripe artefacts are often observed and can deteriorate the image quality. Although the intensity distribution of these artefacts has been described in the literature, their spectral distribution is currently unknown. To assess the spatio-spectral properties of the monochromated X-ray beam, the direct beam has been measured for the first time using a hyperspectral X-ray detector. The results show a large number of spectral features with different spatial distributions for a [Ru, B4C] strip monochromator, associated primarily with the higher-order harmonics of the undulator and monochromator. It is found that their relative contributions are sufficiently low to avoid an influence on the imaging data. The [V, B4C] strip suppresses these high-order harmonics even more than the former, yet at the cost of reduced efficiency.




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White beam diagnostics using X-ray back-scattering from a CVD diamond vacuum window

Collecting back-scattered X-rays from vacuum windows using a pinhole X-ray camera provides an efficient and reliable method of measuring the beam shape and position of the white synchrotron beam. In this paper, measurements are presented that were conducted at ESRF beamline ID6 which uses an in-vacuum cryogenically cooled permanent-magnet undulator (CPMU18) and a traditional U32 undulator as its radiation sources, allowing tests to be performed at very high power density levels that were adjusted by changing the gap of the undulators. These measurements show that it is possible to record beam shape and beam position using a simple geometry without having to place any further items in the beam path. With this simple test setup it was possible to record the beam position with a root-mean-square noise figure of 150 nm.




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A semi-analytical approach for the characterization of ordered 3D nanostructures using grazing-incidence X-ray fluorescence

Following the recent demonstration of grazing-incidence X-ray fluorescence (GIXRF)-based characterization of the 3D atomic distribution of different elements and dimensional parameters of periodic nanoscale structures, this work presents a new computational scheme for the simulation of the angular-dependent fluorescence intensities from such periodic 2D and 3D nanoscale structures. The computational scheme is based on the dynamical diffraction theory in many-beam approximation, which allows a semi-analytical solution to the Sherman equation to be derived in a linear-algebraic form. The computational scheme has been used to analyze recently published GIXRF data measured on 2D Si3N4 lamellar gratings, as well as on periodically structured 3D Cr nanopillars. Both the dimensional and structural parameters of these nanostructures have been reconstructed by fitting numerical simulations to the experimental GIXRF data. Obtained results show good agreement with nominal parameters used in the manufacturing of the structures, as well as with reconstructed parameters based on the previously published finite-element-method simulations, in the case of the Si3N4 grating.




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Understanding the mechanical limitations of the performance of soft X-ray monochromators at MAX IV laboratory

MAX IV is a fourth-generation, or diffraction-limited, synchrotron light source with a number of state-of-the-art beamlines. The performance of a beamline is, to a high degree, set by the energy resolution it can achieve, which in turn is governed to a large extent by the monochromator. During the design phase of a monochromator, the mechanical requirements must be fully understood and met with margin. During commissioning, the performance must be verified and optimized. In this paper, six soft X-ray monochromators at MAX IV beamlines (Bloch, Veritas, HIPPIE, SPECIES, FinEstBeAMS and SoftiMAX) are examined with a focus on their resolving power, energy range and the time required to change measurement range, as those parameters are dependent on each other. The monochromators have a modern commercial design, planned and developed in close collaboration with the vendors. This paper aims to present the current status of the commissioning at MAX IV with emphasis on elucidating the mechanical limitations on the performance of the monochromators. It contains analysis of the outcome and our approach to achieve fast and high-resolution monochromators.




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Foreword to the special virtual issue dedicated to the proceedings of the PhotonDiag2018 workshop on FEL Photon Diagnostics, Instrumentation, and Beamlines Design




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Molecular self-assembly of nylon-12 nanorods cylindrically confined to nanoporous alumina

It has been revealed that in cylindrical nano-confinement, the hydrogen-bonding direction of nylon-12 crystals in the rod could self-assemble to be parallel to the long axis of the rod. The dominant growth direction and hydrogen-bonding direction of the γ-form crystal in the long axis of the rod has been revealed by TEM–SAED and WAXD.




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Nanocrystalline materials: recent advances in crystallographic characterization techniques

This feature article reviews the control and understanding of nanoparticle shape from their crystallography and growth. Particular emphasis is placed on systems relevant for plasmonics and catalysis.




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EXAFS and XANES analysis of oxides at the nanoscale

This work presents a discussion of the possibilities offered by X-ray absorption spectroscopy (XAS) to study the local structure of nanomaterials. The current state of the art for the interpretation of extended X-ray absorption fine structure (EXAFS), including an advanced approach based on the use of classical molecular dynamics, is described and exemplified in the case of NiO nanoparticles. In addition, the limits and possibilities of X-ray absorption near-edge spectroscopy (XANES) in determining several effects associated with the nanocrystalline nature of materials are also discussed in connection with the development of ZnO-based dilute magnetic semiconductors and iron oxide nanoparticles.




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X-ray techniques for innovation in industry

Are synchrotrons needed for innovation in industry? What can scientists at large-scale facilities offer for R&D in industry? Is the comfort of life profiting from research?


























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Characterization of the Pseudomonas aeruginosa T6SS PldB immunity proteins PA5086, PA5087 and PA5088 explains a novel stockpiling mechanism

The bacterial type VI secretion system (T6SS) secretes many toxic effectors to gain advantage in interbacterial competition and for eukaryotic host infection. The cognate immunity proteins of these effectors protect bacteria from their own effectors. PldB is a T6SS trans-kingdom effector in Pseudomonas aeruginosa that can infect both prokaryotic and eukaryotic cells. Three proteins, PA5086, PA5087 and PA5088, are employed to suppress the toxicity of PldB-family proteins. The structures of PA5087 and PA5088 have previously been reported, but the identification of further distinctions between these immunity proteins is needed. Here, the crystal structure of PA5086 is reported at 1.90 Å resolution. A structural comparison of the three PldB immunity proteins showed vast divergences in their electrostatic potential surfaces. This interesting phenomenon provides an explanation of the stockpiling mechanism of T6SS immunity proteins.




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Crystal structure of the nucleoid-associated protein Fis (PA4853) from Pseudomonas aeruginosa

Factor for inversion stimulation (Fis) is a versatile bacterial nucleoid-associated protein that can directly bind and bend DNA to influence DNA topology. It also plays crucial roles in regulating bacterial virulence factors and in optimizing bacterial adaptation to various environments. Fis from Pseudomonas aeruginosa (PA4853, referred to as PaFis) has recently been found to be required for virulence by regulating the expression of type III secretion system (T3SS) genes. PaFis can specifically bind to the promoter region of exsA, which functions as a T3SS master regulator, to regulate its expression and plays an essential role in transcription elongation from exsB to exsA. Here, the crystal structure of PaFis, which is composed of a four-helix bundle and forms a homodimer, is reported. PaFis shows remarkable structural similarities to the well studied Escherichia coli Fis (EcFis), including an N-terminal flexible loop and a C-terminal helix–turn–helix (HTH) motif. However, the critical residues for Hin-catalyzed DNA inversion in the N-terminal loop of EcFis are not conserved in PaFis and further studies are required to investigate its exact role. A gel-electrophoresis mobility-shift assay showed that PaFis can efficiently bind to the promoter region of exsA. Structure-based mutagenesis revealed that several conserved basic residues in the HTH motif play essential roles in DNA binding. These structural and biochemical studies may help in understanding the role of PaFis in the regulation of T3SS expression and in virulence.




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Structure of the 4-hydroxy-tetrahydrodipicolinate synthase from the thermoacidophilic methanotroph Methylacidiphilum fumariolicum SolV and the phylogeny of the aminotransferase pathway

The enzyme 4-hydroxy-tetrahydrodipicolinate synthase (DapA) is involved in the production of lysine and precursor molecules for peptidoglycan synthesis. In a multistep reaction, DapA converts pyruvate and l-aspartate-4-semialdehyde to 4-hydroxy-2,3,4,5-tetrahydrodipicolinic acid. In many organisms, lysine binds allosterically to DapA, causing negative feedback, thus making the enzyme an important regulatory component of the pathway. Here, the 2.1 Å resolution crystal structure of DapA from the thermoacidophilic methanotroph Methylacidiphilum fumariolicum SolV is reported. The enzyme crystallized as a contaminant of a protein preparation from native biomass. Genome analysis reveals that M. fumariolicum SolV utilizes the recently discovered aminotransferase pathway for lysine biosynthesis. Phylogenetic analyses of the genes involved in this pathway shed new light on the distribution of this pathway across the three domains of life.




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Chirality in Biological Nanospaces: Reactions in Active Sites. By Nilashis Nandi. Pp. 209. CRC Press, 2011. Price £79.99. ISBN 9781439840023.




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Exploring the complex map of insulin polymorphism: a novel crystalline form in the presence of m-cresol

A novel monoclinic phase of human insulin co-crystallized with m-cresol was structurally characterized by means of powder and single-crystal X-ray diffraction.




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Structure of P46, an immunodominant surface protein from Mycoplasma hyopneumoniae: interaction with a monoclonal antibody

Structures of the immunodominant protein P46 from M. hyopneumoniae has been determined by X-ray crystallography and it is shown that P46 can bind a diversity of oligosaccharides, particularly xylose, which exhibits a very high affinity for this protein. Structures of a monoclonal antibody, both alone and in complex with P46, that was raised against M. hyopnemoniae cells and specifically recognizes P46 are also reported.




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Structural and thermodynamic analysis of interactions between death-associated protein kinase 1 and anthraquinones

Death-associated protein kinase 1 (DAPK1) was found to form a complex with purpurin and the crystal structure of the complex was determined. Purpurin may be a good lead compound for for the discovery of inhibitors of DAPK1.




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6-Amino-2-iminiumyl-4-oxo-1,2,3,4-tetra­hydro­pyrimidin-5-aminium sulfate monohydrate

The title compound, C4H9N5O2+·SO42−·H2O, is the monohydrate of the commercially available compound `C4H7N5O·H2SO4·xH2O'. It is obtained by reprecipitation of C4H7N5O·H2SO4·xH2O from dilute sodium hydroxide solution with dilute sulfuric acid. The crystal structure of anhydrous 2,4,5-tri­amino-1,6-di­hydro­pyrimidin-6-one sulfate is known, although called by the authors 5-amminium-6-amino-isocytosinium sulfate [Bieri et al. (1993). Private communication (refcode HACDEU). CCDC, Cambridge, England]. In the structure, the sulfate group is deprotonated, whereas one of the amino groups is protonated (R2C—NH3+) and one is rearranged to a protonated imine group (R2C=NH2+). This arrangement is very similar to the known crystal structure of the anhydrate. Several tautomeric forms of the investigated mol­ecule are possible, which leads to questionable proton attributions. The measured data allowed the location of all hydrogen atoms from the residual electron density. In the crystal, ions and water mol­ecules are linked into a three-dimensional network by N—H⋯O and O—H⋯O hydrogen bonds.




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Di­chlorido­{N,N,N'-trimethyl-N'-(1H-pyrazol-1-yl-κN2)meth­yl]ethane-1,2-di­amine-κ2N,N'}copper(II) methanol monosolvate

In the title compound, [CuCl2(C9H18N4)]·CH3OH, the central CuII ion is coordinated by three N atoms from the pyrazole derivative ligand and two chloride co-ligands. The coordination geometry around the CuII ion is distorted trigonal–bipyramidal. In the crystal, the mol­ecules are linked by C—H⋯O, C—H⋯Cl and O—H⋯Cl hydrogen bonds, forming a three-dimensional framework with the lattice solvent mol­ecule.




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2-Amino-6-chloro­pyridine–glutaric acid (1/1)

In the title 1:1 co-crystal [systematic name: 6-chloro­pyridin-2-amine–penta­nedioic acid (1/1)], C5H5ClN2·C5H8O4, the pyridine ring is essentially planar, with a maximum deviation of 0.003 (1) Å. The base and acid mol­ecules are linked via N—H⋯O and O—H⋯N hydrogen bonds, while inversion-related acid mol­ecules are linked via pairs of O—H⋯O hydrogen bonds. These inter­actions together with a C—H⋯O hydrogen bond connect the two components, forming (001) sheets.




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(E)-4-Iodo-2-[(phenyl­imino)­meth­yl]phenol

The title compound, C13H10INO, is not planar as the dihedral angle between the planes of the two aryl rings is 44.5 (9)°. The configuration about the central C=N bond is E, and there is an intra­molecular O—H⋯N hydrogen bond which generates an S(6) ring. The mol­ecular packing is stabilized by weak C—H⋯π inter­actions. The structure was refined as a two-component inversion twin.