nation United Nations Ratifies Framework to Protect People on Cash Apps By www.newswise.com Published On :: Fri, 08 Nov 2024 09:05:00 EST University of Florida cybersecurity professor Kevin Butler developed the framework, which spells out guidance for countries to prevent fraud and abuse on mobile cash apps. Full Article
nation Conceptualizing International New Ventures as the Nexus of Entrepreneurship and International Business By www.newswise.com Published On :: Mon, 11 Nov 2024 10:35:56 EST Full Article
nation Itaewon Tragedy Remembered Nationwide on Second Anniversary By world.kbs.co.kr Published On :: Tue, 29 Oct 2024 16:39:14 +0900 [Domestic] : Memorial events are taking place across the country to honor the victims of the Itaewon crowd crush on Tuesday, the second anniversary of the tragedy. Earlier in the day, a memorial event at the National Assembly brought together survivors, members of the bereaved families, the National Assembly ...[more...] Full Article Domestic
nation Power Broker Myung Tae-kyun Denies Involvement in Election Nomination Scandal By world.kbs.co.kr Published On :: Sun, 10 Nov 2024 11:31:06 +0900 [Politics] : Myung Tae-kyun, a self-proclaimed political consultant and a key figure in a high-profile scandal involving the president and first lady, was questioned by the prosecution for the second consecutive day on Saturday. The Changwon District Prosecutors' Office grilled Myung for over 12 hours on Saturday ...[more...] Full Article Politics
nation NIS Assesses N. Korean Leader Upgrading Security Due to Assassination Concerns By world.kbs.co.kr Published On :: Tue, 29 Oct 2024 16:45:56 +0900 [Inter-Korea] : South Korea's intelligence agency assessed that North Korean leader Kim Jong-un has begun to upgrade his security due to concerns over a potential assassination attempt. According to rival political parties on the parliamentary Intelligence Committee on Tuesday, the assessment was made by the ...[more...] Full Article Inter-Korea
nation Ex-National Football Team Player Receives Permanent Ban from Chinese Football Association By world.kbs.co.kr Published On :: Tue, 10 Sep 2024 16:43:39 +0900 [Sports] : Former national football team member Son Jun-ho has been permanently banned by the Chinese Football Association(CFA). The CFA on Tuesday announced the disciplinary action against Son, accusing the football player of engaging in match-fixing and bribery. With the latest decision, Son is permanently ...[more...] Full Article Sports
nation National Football Team to Keep Tab on Son's Injury Ahead of World Cup Qualifiers By world.kbs.co.kr Published On :: Mon, 30 Sep 2024 15:22:27 +0900 [Sports] : Men's national football team head coach Hong Myung-bo has cast doubt over captain Son Heung-min's availability in the upcoming World Cup qualifiers next month. During a press conference on Monday, Hong announced the roster for October's World Cup qualifiers, which included the Tottenham Hotspur star ...[more...] Full Article Sports
nation Men's National Football Team Face Iraq in World Cup Qualifier By world.kbs.co.kr Published On :: Tue, 15 Oct 2024 15:15:11 +0900 [Sports] : The South Korean men's national football team faces Iraq in the World Cup qualifier match on Tuesday night at home. Considered the toughest opponent for South Korea in the third round of the Asian qualifiers, a win against the Middle Eastern squad will give the Taegeuk Warriors a huge boost in their ...[more...] Full Article Sports
nation Son Heung-min Returns as National Team Faces Kuwait, Palestine in World Cup Qualifiers By world.kbs.co.kr Published On :: Mon, 04 Nov 2024 15:51:08 +0900 [Sports] : The men’s national football team is set to face Kuwait and Palestine in mid-November in the third round of 2026 FIFA World Cup qualifiers with the return of captain Son Heung-min, who sat out matches in October due to a hamstring injury. Head coach Hong Myung-bo announced the 26-member roster on Monday, ...[more...] Full Article Sports
nation Heavy Rain Warning and Watch in place For Most Parts of Nation By world.kbs.co.kr Published On :: Fri, 20 Sep 2024 17:44:26 +0900 [Science] : A heavy rain warning has been issued for the five border islands in the Yellow Sea and a heavy rain watch for the Seoul metro area, Gangwon Province and parts of the Jeolla and Gyeongsang provinces. With heavy rain set to pound most parts of the nation through Sunday, the interior and safety ministry on ...[more...] Full Article Science
nation Most of Nation to See Rain through Saturday By world.kbs.co.kr Published On :: Fri, 18 Oct 2024 14:11:24 +0900 [Science] : Most parts of the nation are experiencing heavy rain, with up to 120 millimeters expected in some areas through Saturday. The Korea Meteorological Administration forecast on Friday that the eastern coastal areas of Gangwon Province will see 50 to 100 millimeters of rain through Saturday, adding that ...[more...] Full Article Science
nation Rain Forecast Nationwide, with Downpours along Southern Coast, on Jeju Island By world.kbs.co.kr Published On :: Tue, 22 Oct 2024 14:44:23 +0900 [Science] : Rain is in the forecast nationwide on Tuesday, with downpours expected along the southern coastal areas of South Jeolla Province, in the southeastern Gyeongsang region and on the southernmost island of Jeju. According to the Korea Meteorological Administration, over 100 millimeters could fall on the ...[more...] Full Article Science
nation PM Han in Hangeul Day Speech: Nation Has Duty to Further Develop Korean Alphabet By world.kbs.co.kr Published On :: Wed, 09 Oct 2024 14:17:51 +0900 [Culture] : Prime Minister Han Duck-soo said the nation has a duty to further develop the Korean alphabet, hangeul, which has gained worldwide recognition as a unique writing system. At a government ceremony marking the 578th Hangeul Day on Wednesday, Han raised concerns about “indifference to the Korean language” ...[more...] Full Article Culture
nation BGS updates national CO2 storage database - Agg-Net By news.google.com Published On :: Tue, 30 Jan 2024 08:00:00 GMT BGS updates national CO2 storage database Agg-Net Full Article
nation International geoscience - British Geological Survey By news.google.com Published On :: Tue, 16 May 2023 15:11:39 GMT International geoscience British Geological Survey Full Article
nation First national-scale groundwater model in Great Britain developed - British Geological Survey By news.google.com Published On :: Tue, 14 May 2024 10:50:37 GMT First national-scale groundwater model in Great Britain developed British Geological Survey Full Article
nation BGS to help deliver International Centre of Excellence on Sustainable Resource Management - British Geological Survey By news.google.com Published On :: Tue, 27 Feb 2024 16:32:42 GMT BGS to help deliver International Centre of Excellence on Sustainable Resource Management British Geological Survey Full Article
nation International geoscience research and development - British Geological Survey By news.google.com Published On :: Sat, 20 Jan 2024 09:25:00 GMT International geoscience research and development British Geological Survey Full Article
nation From `crystallographic accuracy' to `thermodynamic accuracy': a redetermination of the crystal structure of calcium atorvastatin trihydrate (Lipitor®) By journals.iucr.org Published On :: The crystal structure of calcium atorvastatin trihydrate was redetermined from previously published synchrotron powder diffraction data to give a much-improved agreement with two independent density-functional theory calculations. Full Article text
nation Coordination geometry flexibility driving supramolecular isomerism of Cu/Mo pillared-layer hybrid networks By journals.iucr.org Published On :: The hydrothermal synthesis and structural characterization of four novel 3D pillared-layer metal–organic frameworks are studied, revealing how the malleability of copper coordination geometries drives diverse supramolecular isomerism. The findings provide new insights into designing advanced hybrid materials with tailored properties, emphasizing the significant role of reaction conditions and metal ion flexibility in determining network topologies. Full Article text
nation From `crystallographic accuracy' to `thermodynamic accuracy': a redetermination of the crystal structure of calcium atorvastatin trihydrate (Lipitor®) By journals.iucr.org Published On :: 2024-10-08 With ever-improving quantum-mechanical computational methods, the accuracy requirements for experimental crystal structures increase. The crystal structure of calcium atorvastatin trihydrate, which has 56 degrees of freedom when determined with a real-space algorithm, was determined from powder diffraction data by Hodge et al. [Powder Diffr. (2020), 35, 136–143]. The crystal structure was a good fit to the experimental data, indicating that the electron density had been captured essentially correctly, but two independent quantum-mechanical calculations disagreed with the experimental structure and with each other. Using the same experimental data, the crystal structure was redetermined from scratch and it was shown that it can be reproduced within a root-mean-square Cartesian displacement of 0.1 Å by two independent quantum-mechanical calculations. The consequences for the calculated energies and solubilities are described. Full Article text
nation Combination of XEOL, TR-XEOL and HB-T interferometer at the TPS 23A X-ray nanoprobe for exploring quantum materials By journals.iucr.org Published On :: 2024-01-19 In this study, a combination of X-ray excited optical luminescence (XEOL), time-resolved XEOL (TR-XEOL) and the Hanbury-Brown and Twiss (HB-T) interferometer at the Taiwan Photon Source (TPS) 23A X-ray nanoprobe beamline for exploring quantum materials is demonstrated. On the basis of the excellent spatial resolution rendered using a nano-focused beam, emission distributions of artificial micro-diamonds can be obtained by XEOL maps, and featured emission peaks of a selected local area can be obtained by XEOL spectra. The hybrid bunch mode of the TPS not only provides a sufficiently high peak power density for experiments at each beamline but also permits high-quality temporal domain (∼200 ns) measurements for investigating luminescence dynamics. From TR-XEOL measurements, the decay lifetime of micro-diamonds is determined to be approximately 16 ns. Furthermore, the XEOL spectra of artificial micro-diamonds can be investigated by the HB-T interferometer to identify properties of single-photon sources. The unprecedented strategy of combining XEOL, TR-XEOL and the HB-T interferometer at the X-ray nanoprobe beamline will open new avenues with significant characterization abilities for unraveling the emission mechanisms of single-photon sources for quantum materials. Full Article text
nation Determination of optimal experimental conditions for accurate 3D reconstruction of the magnetization vector via XMCD-PEEM By journals.iucr.org Published On :: 2024-02-19 This work presents a detailed analysis of the performance of X-ray magnetic circular dichroism photoemission electron microscopy (XMCD-PEEM) as a tool for vector reconstruction of magnetization. For this, 360° domain wall ring structures which form in a synthetic antiferromagnet are chosen as the model to conduct the quantitative analysis. An assessment is made of how the quality of the results is affected depending on the number of projections that are involved in the reconstruction process, as well as their angular distribution. For this a self-consistent error metric is developed which allows an estimation of the optimum azimuthal rotation angular range and number of projections. This work thus proposes XMCD-PEEM as a powerful tool for vector imaging of complex 3D magnetic structures. Full Article text
nation Improving sensitivity of XANES structural fit to the bridged metal–metal coordination By journals.iucr.org Published On :: 2024-03-26 Hard X-ray absorption spectroscopy is a valuable in situ probe for non-destructive diagnostics of metal sites. The low-energy interval of a spectrum (XANES) contains information about the metal oxidation state, ligand type, symmetry and distances in the first coordination shell but shows almost no dependency on the bridged metal–metal bond length. The higher-energy interval (EXAFS), on the contrary, is more sensitive to the coordination numbers and can decouple the contribution from distances in different coordination shells. Supervised machine-learning methods can combine information from different intervals of a spectrum; however, computational approaches for the near-edge region of the spectrum and higher energies are different. This work aims to keep all benefits of XANES and extend its sensitivity towards the interatomic distances in the first and second coordination shells. Using a binuclear bridged copper complex as a case study and cross-validation analysis as a quantitative tool it is shown that the first 170 eV above the edge are already sufficient to balance the contributions of Cu–O/N scattering and Cu–Cu scattering. As a more general outcome this work highlights the trivial but often overlooked importance of using `longer' energy intervals of XANES for structural refinement and machine-learning predictions. The first 200 eV above the absorption edge still do not require parametrization of Debye–Waller damping and can be calculated within full multiple scattering or finite difference approximations with only moderately increased computational costs. Full Article text
nation PEPICO analysis of catalytic reactor effluents towards quantitative isomer discrimination: DME conversion over a ZSM-5 zeolite By journals.iucr.org Published On :: 2024-06-25 The methanol-to-hydrocarbons (MTH) process involves the conversion of methanol, a C1 feedstock that can be produced from green sources, into hydrocarbons using shape-selective microporous acidic catalysts – zeolite and zeotypes. This reaction yields a complex mixture of species, some of which are highly reactive and/or present in several isomeric forms, posing significant challenges for effluent analysis. Conventional gas-phase chromatography (GC) is typically employed for the analysis of reaction products in laboratory flow reactors. However, GC is not suitable for the detection of highly reactive intermediates such as ketene or formaldehyde and is not suitable for kinetic studies under well defined low pressure conditions. Photoelectron–photoion coincidence (PEPICO) spectroscopy has emerged as a powerful analytical tool for unraveling complex compositions of catalytic effluents, but its availability is limited to a handful of facilities worldwide. Herein, PEPICO analysis of catalytic reactor effluents has been implemented at the FinEstBeAMS beamline of MAX IV Laboratory. The conversion of dimethyl ether (DME) on a zeolite catalyst (ZSM-5-MFI27) is used as a prototypical model reaction producing a wide distribution of hydrocarbon products. Since in zeolites methanol is quickly equilibrated with DME, this reaction can be used to probe vast sub-networks of the full MTH process, while eliminating or at least slowing down methanol-induced secondary reactions and catalyst deactivation. Quantitative discrimination of xylene isomers in the effluent stream is achieved by deconvoluting the coincidence photoelectron spectra. Full Article text
nation Redetermination of germacrone type II based on single-crystal X-ray data By journals.iucr.org Published On :: 2024-04-26 The extraction and purification procedures, crystallization and crystal structure refinement (single-crystal X-ray data) of germacrone type II, C15H22O, are presented. The structural results are compared with a previous powder X-ray synchrotron study [Kaduk et al. (2022). Powder Diffr. 37, 98–104], revealing significant improvements in terms of accuracy and precision. Hirshfeld atom refinement (HAR), as well as Hirshfeld surface analysis, give insight into the intermolecular interactions of germacrone type II. Full Article text
nation Using synchrotron high-resolution powder X-ray diffraction for the structure determination of a new cocrystal formed by two active principle ingredients By journals.iucr.org Published On :: 2024-01-28 The crystal structure of a new 1:1 cocrystal of carbamazepine and S-naproxen (C15H12N2O·C14H14O3) was solved from powder X-ray diffraction (PXRD). The PXRD pattern was measured at the high-resolution beamline CRISTAL at synchrotron SOLEIL (France). The structure was solved using Monte Carlo simulated annealing, then refined with Rietveld refinement. The positions of the H atoms were obtained from density functional theory (DFT) ground-state calculations. The symmetry is orthorhombic with the space group P212121 (No. 19) and the following lattice parameters: a = 33.5486 (9), b = 26.4223 (6), c = 5.3651 (10) Å and V = 4755.83 (19) Å3. Full Article text
nation Absolute structure determination of Berkecoumarin by X-ray and electron diffraction By journals.iucr.org Published On :: 2024-04-10 X-ray and electron diffraction methods independently identify the S-enantiomer of Berkecoumarin [systematic name: (S)-8-hydroxy-3-(2-hydroxypropyl)-6-methoxy-2H-chromen-2-one]. Isolated from Berkeley Pit Lake Penicillium sp., Berkecoumarin is a natural product with a light-atom composition (C13H14O5) that challenges in-house absolute structure determination by anomalous scattering. This study further demonstrates the utility of dynamical refinement of electron-diffraction data for absolute structure determination. Full Article text
nation Salt forms of amides: protonation of acetanilide By journals.iucr.org Published On :: 2024-08-06 Treating the amide acetanilide (N-phenylacetamide, C8H9NO) with aqueous strong acids allowed the structures of five hemi-protonated salt forms of acetanilide to be elucidated. N-(1-Hydroxyethylidene)anilinium chloride–N-phenylacetamide (1/1), [(C8H9NO)2H][Cl], and the bromide, [(C8H9NO)2H][Br], triiodide, [(C8H9NO)2H][I3], tetrafluoroborate, [(C8H9NO)2H][BF4], and diiodobromide hemi(diiodine), [(C8H9NO)2H][I2Br]·0.5I2, analogues all feature centrosymmetric dimeric units linked by O—H⋯O hydrogen bonds that extend into one-dimensional hydrogen-bonded chains through N—H⋯X interactions, where X is the halide atom of the anion. Protonation occurs at the amide O atom and results in systematic lengthening of the C=O bond and a corresponding shortening of the C—N bond. The size of these geometric changes is similar to those found for hemi-protonated paracetamol structures, but less than those in fully protonated paracetamol structures. The bond angles of the amide fragments are also found to change on protonation, but these angular changes are also influenced by conformation, namely, whether the amide group is coplanar with the phenyl ring or twisted out of plane. Full Article text
nation Coordination variety of phenyltetrazolato and dimethylamido ligands in dimeric Ti, Zr, and Ta complexes By journals.iucr.org Published On :: 2024-08-23 Three structurally diverse 5-phenyltetrazolato (Tz) Ti, Zr, and Ta complexes, namely, (C2H8N)[Ti2(C7H5N4)5(C2H6N)4]·1.45C6H6 or (Me2NH2)[Ti2(NMe2)4(2,3-μ-Tz)3(2-η1-Tz)2]·1.45C6H6, (1·1.45C6H6), [Zr2(C7H5N4)6(C2H6N)2(C2H7N)2]·1.12C6H6·0.382CH2Cl2 or [Zr2(Me2NH)2(NMe2)2(2,3-μ-Tz)3(2-η1-Tz)2(1,2-η2-Tz)]·1.12C6H6·0.38CH2Cl2 (2·1.12C6H6·0.38CH2Cl2), and (C2H8N)2[Ta2(C7H5N4)8(C2H6N)2O]·0.25C7H8 or (Me2NH2)2[Ta2(NMe2)2(2,3-μ-Tz)2(2-η1-Tz)6O]·0.25C7H8 (3·0.25C7H8), where TzH is 5-phenyl-1H-tetrazole, have been synthesized and structurally characterized. All three complexes are dinuclear; the Ti center in 1 is six-coordinate, whereas the Zr and Ta atoms in 2 and 3 are seven-coordinate. The coordination environments of the Ti centers in 1 are similar, and so are the ligations of the Ta centers in 3. In contrast, the two Zr centers in 2 bear a different number of ligands, one of which is a bidentate η2-5-phenyltetrazolato ligand that has not been observed previously for d-block elements. The dimethylamido ligand, present in the starting materials, remained unchanged, or was converted to dimethylamine and dimethylammonium during the synthesis. Dimethylamine coordinates as a neutral ligand, whereas dimethylammonium is retained as a hydrogen-bonded entity bridging Tz ligands. Full Article text
nation Coordination structure and intermolecular interactions in copper(II) acetate complexes with 1,10-phenanthroline and 2,2'-bipyridine By journals.iucr.org Published On :: 2024-08-23 The crystal structures of two coordination compounds, (acetato-κO)(2,2'-bipyridine-κ2N,N')(1,10-phenanthroline-κ2N,N')copper(II) acetate hexahydrate, [Cu(C2H3O2)(C10H8N2)(C12H8N2)](C2H3O2)·6H2O or [Cu(bipy)(phen)Ac]Ac·6H2O, and (acetato-κO)bis(2,2'-bipyridine-κ2N,N')copper(II) acetate–acetic acid–water (1/1/3), [Cu(C2H3O2)(C10H8N2)2](C2H3O2)·C2H4O2·3H2O or [Cu(bipy)2Ac]Ac·HAc·3H2O, are reported and compared with the previously published structure of [Cu(phen)2Ac]Ac·7H2O (phen is 1,10-phenanthroline, bipy for 2,2'-bipyridine, ac is acetate and Hac is acetic acid). The geometry around the metal centre is pentacoordinated, but highly distorted in all three cases. The coordination number and the geometric distortion are both discussed in detail, and all complexes belong to the space group Poverline{1}. The analysis of the geometric parameters and the Hirshfeld surface properties dnorm and curvedness provide information about the metal–ligand interactions in these complexes and allow comparison with similar systems. Full Article text
nation AlphaFold-assisted structure determination of a bacterial protein of unknown function using X-ray and electron crystallography By journals.iucr.org Published On :: 2024-03-07 Macromolecular crystallography generally requires the recovery of missing phase information from diffraction data to reconstruct an electron-density map of the crystallized molecule. Most recent structures have been solved using molecular replacement as a phasing method, requiring an a priori structure that is closely related to the target protein to serve as a search model; when no such search model exists, molecular replacement is not possible. New advances in computational machine-learning methods, however, have resulted in major advances in protein structure predictions from sequence information. Methods that generate predicted structural models of sufficient accuracy provide a powerful approach to molecular replacement. Taking advantage of these advances, AlphaFold predictions were applied to enable structure determination of a bacterial protein of unknown function (UniProtKB Q63NT7, NCBI locus BPSS0212) based on diffraction data that had evaded phasing attempts using MIR and anomalous scattering methods. Using both X-ray and micro-electron (microED) diffraction data, it was possible to solve the structure of the main fragment of the protein using a predicted model of that domain as a starting point. The use of predicted structural models importantly expands the promise of electron diffraction, where structure determination relies critically on molecular replacement. Full Article text
nation Structural determination and modeling of ciliary microtubules By journals.iucr.org Published On :: 2024-03-07 The axoneme, a microtubule-based array at the center of every cilium, has been the subject of structural investigations for decades, but only recent advances in cryo-EM and cryo-ET have allowed a molecular-level interpretation of the entire complex to be achieved. The unique properties of the nine doublet microtubules and central pair of singlet microtubules that form the axoneme, including the highly decorated tubulin lattice and the docking of massive axonemal complexes, provide opportunities and challenges for sample preparation, 3D reconstruction and atomic modeling. Here, the approaches used for cryo-EM and cryo-ET of axonemes are reviewed, while highlighting the unique opportunities provided by the latest generation of AI-guided tools that are transforming structural biology. Full Article text
nation A database overview of metal-coordination distances in metalloproteins By journals.iucr.org Published On :: 2024-04-29 Metalloproteins are ubiquitous in all living organisms and take part in a very wide range of biological processes. For this reason, their experimental characterization is crucial to obtain improved knowledge of their structure and biological functions. The three-dimensional structure represents highly relevant information since it provides insight into the interaction between the metal ion(s) and the protein fold. Such interactions determine the chemical reactivity of the bound metal. The available PDB structures can contain errors due to experimental factors such as poor resolution and radiation damage. A lack of use of distance restraints during the refinement and validation process also impacts the structure quality. Here, the aim was to obtain a thorough overview of the distribution of the distances between metal ions and their donor atoms through the statistical analysis of a data set based on more than 115 000 metal-binding sites in proteins. This analysis not only produced reference data that can be used by experimentalists to support the structure-determination process, for example as refinement restraints, but also resulted in an improved insight into how protein coordination occurs for different metals and the nature of their binding interactions. In particular, the features of carboxylate coordination were inspected, which is the only type of interaction that is commonly present for nearly all metals. Full Article text
nation Deep-learning map segmentation for protein X-ray crystallographic structure determination By journals.iucr.org Published On :: 2024-06-27 When solving a structure of a protein from single-wavelength anomalous diffraction X-ray data, the initial phases obtained by phasing from an anomalously scattering substructure usually need to be improved by an iterated electron-density modification. In this manuscript, the use of convolutional neural networks (CNNs) for segmentation of the initial experimental phasing electron-density maps is proposed. The results reported demonstrate that a CNN with U-net architecture, trained on several thousands of electron-density maps generated mainly using X-ray data from the Protein Data Bank in a supervised learning, can improve current density-modification methods. Full Article text
nation Protonation of histidine rings using quantum-mechanical methods By journals.iucr.org Published On :: 2024-07-25 Histidine can be protonated on either or both of the two N atoms of the imidazole moiety. Each of the three possible forms occurs as a result of the stereochemical environment of the histidine side chain. In an atomic model, comparing the possible protonation states in situ, looking at possible hydrogen bonding and metal coordination, it is possible to predict which is most likely to be correct. A more direct method is described that uses quantum-mechanical methods to calculate, also in situ, the minimum geometry and energy for comparison, and therefore to more accurately identify the most likely protonation state. Full Article text
nation STEM SerialED: achieving high-resolution data for ab initio structure determination of beam-sensitive nanocrystalline materials By journals.iucr.org Published On :: 2024-01-01 Serial electron diffraction (SerialED), which applies a snapshot data acquisition strategy for each crystal, was introduced to tackle the problem of radiation damage in the structure determination of beam-sensitive materials by three-dimensional electron diffraction (3DED). The snapshot data acquisition in SerialED can be realized using both transmission and scanning transmission electron microscopes (TEM/STEM). However, the current SerialED workflow based on STEM setups requires special external devices and software, which limits broader adoption. Here, we present a simplified experimental implementation of STEM-based SerialED on Thermo Fisher Scientific STEMs using common proprietary software interfaced through Python scripts to automate data collection. Specifically, we utilize TEM Imaging and Analysis (TIA) scripting and TEM scripting to access the STEM functionalities of the microscope, and DigitalMicrograph scripting to control the camera for snapshot data acquisition. Data analysis adapts the existing workflow using the software CrystFEL, which was developed for serial X-ray crystallography. Our workflow for STEM SerialED can be used on any Gatan or Thermo Fisher Scientific camera. We apply this workflow to collect high-resolution STEM SerialED data from two aluminosilicate zeolites, zeolite Y and ZSM-25. We demonstrate, for the first time, ab initio structure determination through direct methods using STEM SerialED data. Zeolite Y is relatively stable under the electron beam, and STEM SerialED data extend to 0.60 Å. We show that the structural model obtained using STEM SerialED data merged from 358 crystals is nearly identical to that using continuous rotation electron diffraction data from one crystal. This demonstrates that accurate structures can be obtained from STEM SerialED. Zeolite ZSM-25 is very beam-sensitive and has a complex structure. We show that STEM SerialED greatly improves the data resolution of ZSM-25, compared with serial rotation electron diffraction (SerialRED), from 1.50 to 0.90 Å. This allows, for the first time, the use of standard phasing methods, such as direct methods, for the ab initio structure determination of ZSM-25. Full Article text
nation Structure determination using high-order spatial correlations in single-particle X-ray scattering By journals.iucr.org Published On :: 2024-01-01 Single-particle imaging using X-ray free-electron lasers (XFELs) is a promising technique for observing nanoscale biological samples under near-physiological conditions. However, as the sample's orientation in each diffraction pattern is unknown, advanced algorithms are required to reconstruct the 3D diffraction intensity volume and subsequently the sample's density model. While most approaches perform 3D reconstruction via determining the orientation of each diffraction pattern, a correlation-based approach utilizes the averaged spatial correlations of diffraction intensities over all patterns, making it well suited for processing experimental data with a poor signal-to-noise ratio of individual patterns. Here, a method is proposed to determine the 3D structure of a sample by analyzing the double, triple and quadruple spatial correlations in diffraction patterns. This ab initio method can reconstruct the basic shape of an irregular unsymmetric 3D sample without requiring any prior knowledge of the sample. The impact of background and noise on correlations is investigated and corrected to ensure the success of reconstruction under simulated experimental conditions. Additionally, the feasibility of using the correlation-based approach to process incomplete partial diffraction patterns is demonstrated. The proposed method is a variable addition to existing algorithms for 3D reconstruction and will further promote the development and adoption of XFEL single-particle imaging techniques. Full Article text
nation A modified phase-retrieval algorithm to facilitate automatic de novo macromolecular structure determination in single-wavelength anomalous diffraction By journals.iucr.org Published On :: 2024-06-21 The success of experimental phasing in macromolecular crystallography relies primarily on the accurate locations of heavy atoms bound to the target crystal. To improve the process of substructure determination, a modified phase-retrieval algorithm built on the framework of the relaxed alternating averaged reflection (RAAR) algorithm has been developed. Importantly, the proposed algorithm features a combination of the π-half phase perturbation for weak reflections and enforces the direct-method-based tangent formula for strong reflections in reciprocal space. The proposed algorithm is extensively demonstrated on a total of 100 single-wavelength anomalous diffraction (SAD) experimental datasets, comprising both protein and nucleic acid structures of different qualities. Compared with the standard RAAR algorithm, the modified phase-retrieval algorithm exhibits significantly improved effectiveness and accuracy in SAD substructure determination, highlighting the importance of additional constraints for algorithmic performance. Furthermore, the proposed algorithm can be performed without human intervention under most conditions owing to the self-adaptive property of the input parameters, thus making it convenient to be integrated into the structural determination pipeline. In conjunction with the IPCAS software suite, we demonstrated experimentally that automatic de novo structure determination is possible on the basis of our proposed algorithm. Full Article text
nation Fixed-target pump–probe SFX: eliminating the scourge of light contamination By journals.iucr.org Published On :: 2024-07-09 X-ray free-electron laser (XFEL) light sources have enabled the rapid growth of time-resolved structural experiments, which provide crucial information on the function of macromolecules and their mechanisms. Here, the aim was to commission the SwissMX fixed-target sample-delivery system at the SwissFEL Cristallina experimental station using the PSI-developed micro-structured polymer (MISP) chip for pump–probe time-resolved experiments. To characterize the system, crystals of the light-sensitive protein light–oxygen–voltage domain 1 (LOV1) from Chlamydomonas reinhardtii were used. Using different experimental settings, the accidental illumination, referred to as light contamination, of crystals mounted in wells adjacent to those illuminated by the pump laser was examined. It was crucial to control the light scattering from and through the solid supports otherwise significant contamination occurred. However, the results here show that the opaque MISP chips are suitable for defined pump–probe studies of a light-sensitive protein. The experiment also probed the sub-millisecond structural dynamics of LOV1 and indicated that at Δt = 10 µs a covalent thioether bond is established between reactive Cys57 and its flavin mononucleotide cofactor. This experiment validates the crystals to be suitable for in-depth follow-up studies of this still poorly understood signal-transduction mechanism. Importantly, the fixed-target delivery system also permitted a tenfold reduction in protein sample consumption compared with the more common high-viscosity extrusion-based delivery system. This development creates the prospect of an increase in XFEL project throughput for the field. Full Article text
nation Structural characterization of TIR-domain signalosomes through a combination of structural biology approaches By journals.iucr.org Published On :: 2024-08-27 The TIR (Toll/interleukin-1 receptor) domain represents a vital structural element shared by proteins with roles in immunity signalling pathways across phyla (from humans and plants to bacteria). Decades of research have finally led to identifying the key features of the molecular basis of signalling by these domains, including the formation of open-ended (filamentous) assemblies (responsible for the signalling by cooperative assembly formation mechanism, SCAF) and enzymatic activities involving the cleavage of nucleotides. We present a historical perspective of the research that led to this understanding, highlighting the roles that different structural methods played in this process: X-ray crystallography (including serial crystallography), microED (micro-crystal electron diffraction), NMR (nuclear magnetic resonance) spectroscopy and cryo-EM (cryogenic electron microscopy) involving helical reconstruction and single-particle analysis. This perspective emphasizes the complementarity of different structural approaches. Full Article text
nation Tuning structural modulation and magnetic properties in metal–organic coordination polymers [CH3NH3]CoxNi1−x(HCOO)3 By journals.iucr.org Published On :: 2024-09-24 Three solid solutions of [CH3NH3]CoxNi1−x(HCOO)3, with x = 0.25 (1), x = 0.50 (2) and x = 0.75 (3), were synthesized and their nuclear structures and magnetic properties were characterized using single-crystal neutron diffraction and magnetization measurements. At room temperature, all three compounds crystallize in the Pnma orthorhombic space group, akin to the cobalt and nickel end series members. On cooling, each compound undergoes a distinct series of structural transitions to modulated structures. Compound 1 exhibits a phase transition to a modulated structure analogous to the pure Ni compound [Cañadillas-Delgado, L., Mazzuca, L., Fabelo, O., Rodríguez-Carvajal, J. & Petricek, V. (2020). Inorg. Chem. 59, 17896–17905], whereas compound 3 maintains the behaviour observed in the pure Co compound reported previously [Canadillas-Delgado, L., Mazzuca, L., Fabelo, O., Rodriguez-Velamazan, J. A. & Rodriguez-Carvajal, J. (2019). IUCrJ, 6, 105–115], although in both cases the temperatures at which the phase transitions occur differ slightly from the pure phases. Monochromatic neutron diffraction measurements showed that the structural evolution of 2 diverges from that of either parent compound, with competing hydrogen bond interactions that drive the modulation throughout the series, producing a unique sequence of phases. It involves two modulated phases below 96 (3) and 59 (3) K, with different q vectors, similar to the pure Co compound (with modulated phases below 128 and 96 K); however, it maintains the modulated phase below magnetic order [at 22.5 (7) K], resembling the pure Ni compound (which presents magnetic order below 34 K), resulting in an improper modulated magnetic structure. Despite these large-scale structural changes, magnetometry data reveal that the bulk magnetic properties of these solid solutions form a linear continuum between the end members. Notably, doping of the metal site in these solid solutions allows for tuning of bulk magnetic properties, including magnetic ordering temperature, transition temperatures and the nature of nuclear phase transitions, through adjustment of metal ratios. Full Article text
nation Synthesis, crystal structure and hydrogenation properties of MgxLi3 − xB48 − y (x = 1.11, y = 0.40) By journals.iucr.org Published On :: 2024-01-01 The ternary magnesium/lithium boride, MgxLi3 − xB48 − y (x = 1.11, y = 0.40, idealized formula MgLi2B48), crystallizes as its own structure type in P43212, which is closely related to the structural family comprising α-AlB12, Be0.7Al1.1B22 and tetragonal β-boron. The asymmetric unit of title structure contains two statistical mixtures Mg/Li in Wyckoff sites 8b with relative occupancies Mg:Li = 0.495 (9):0.505 (9) and 4a with Mg:Li = 0.097 (8):0.903 (8). The boron atoms occupy 23 8b sites and two 4a sites. One of the latter sites has a partial occupancy factor of 0.61 (2). Both unique Mg/Li atoms adopt a twelvefold coordination environment in the form of truncated tetrahedra (Laves polyhedra). These polyhedra are connected by triangular faces to four [B12] icosahedra. The boron atoms exhibit four kinds of polyhedra, namely pentagonal pyramid (coordination number CN = 6), distorted tetragonal pyramid (CN = 5), bicapped hexagon (CN = 8) and gyrobifastigium (CN = 8). At the gas hydrogenation of MgLi2B48 alloy, formation of the eutectic composite hydride LiBH4+Mg(BH4)2 and amorphous boron is observed. In the temperature range 543–623 K, the hydride eutectics decompose, forming MgH2, LiH, MgB4, B and H2. Full Article text
nation Synthesis and redetermination of the crystal structure of NbF5 By journals.iucr.org Published On :: 2023-11-30 Single crystals of NbF5, niobium(V) fluoride, have been obtained by the reaction of niobium metal in a stream of dilute elemental fluorine at 473 K and subsequent sublimation. The as-obtained bulk phase compound was shown to be pure by powder X-ray diffraction at 293 K and by IR and Raman spectroscopy. A single-crystal X-ray analysis was conducted at 100 K. In comparison to the previously reported structure model [Edwards (1964). J. Chem. Soc. pp. 3714–3718], the lattice parameters and fractional atom coordinates were determined to much higher precision and individual, anisotropic displacement parameters were refined for all atoms. Full Article text
nation The synthesis and structural properties of a chloridobis{N-[(4-methoxyphenyl)imino]pyrrolidine-1-carboxamide}zinc(II) (acetonitrile)trichloridozincate coordination complex By journals.iucr.org Published On :: 2024-01-01 The title complex, [ZnCl(C12H15N3O2)2][ZnCl3(CH3CN)], was synthesized and its structure was fully characterized through single-crystal X-ray diffraction analysis. The complex crystallizes in the orthorhombic system, space group Pbca (61), with a central zinc atom coordinating one chlorine atom and two pyrrolidinyl-4-methoxyphenyl azoformamide ligands in a bidentate manner, utilizing both the nitrogen and oxygen atoms in a 1,3-heterodiene (N=N—C=O) motif for coordinative bonding, yielding an overall positively (+1) charged complex. The complex is accompanied by a [(CH3CN)ZnCl3]− counter-ion. The crystal data show that the harder oxygen atoms in the heterodiene zinc chelate form bonding interactions with distances of 2.002 (3) and 2.012 (3) Å, while nitrogen atoms are coordinated by the central zinc cation with bond lengths of 2.207 (3) and 2.211 (3) Å. To gain further insight into the intermolecular interactions within the crystal, Hirshfeld surface analysis was performed, along with the calculation of two-dimensional fingerprint plots. This analysis revealed that H⋯H (39.9%), Cl⋯H/H⋯Cl (28.2%) and C⋯H/H⋯C (7.2%) interactions are dominant. This unique crystal structure sheds light on arrangement and bonding interactions with azoformamide ligands, and their unique qualities over similar semicarbazone and azothioformamide structures. Full Article text
nation Synthesis and crystal structure of a cadmium(II) coordination polymer based on 4,4'-(1H-1,2,4-triazole-3,5-diyl)dibenzoate By journals.iucr.org Published On :: 2024-01-09 The asymmetric unit of the title compound, catena-poly[[[aquabis(pyridine-κN)cadmium(II)]-μ2-4,4'-(1H-1,2,4-triazole-3,5-diyl)dibenzoato-κ4O,O':O'',O'''] 4.5-hydrate], {[Cd(C16H9N3O4)(C5H5N)2(H2O)]·4.5H2O}n or {[Cd(bct)(py)2(H2O)]·4.5H2O}n (I), consists of a Cd2+ cation coordinated to one bct2– carboxylate dianion, two molecules of pyridine and a water molecule as well as four and a half water molecules of crystallization. The metal ion in I possesses a pentagonal–bipyramidal environment with the four O atoms of the two bidentately coordinated carboxylate groups and the N atom of a pyridine molecule forming the O4N equatorial plane, while the N atom of another pyridine ligand and the O atom of the water molecule occupy the axial positions. The bct2– bridging ligand connects two metal ions via its carboxylic groups, resulting in the formation of a parallel linear polymeric chain running along the [1overline{1}1] direction. The coordinated water molecule of one chain forms a strong O—H⋯O hydrogen bond with the carboxylate O atom of a neighboring chain, leading to the formation of double chains with a closest distance of 5.425 (7) Å between the cadmium ions belonging to different chains. Aromatic π–π stacking interactions between the benzene fragments of the anions as well as between the coordinated pyridine molecules belonging to different chains results in the formation of sheets oriented parallel to the (overline{1}01) plane. As a result of hydrogen-bonding interactions involving the water molecules of crystallization, the sheets are joined together in a three-dimensional network. Full Article text
nation Crystal structure and characterization of a new lanthanide coordination polymer, [Pr2(pydc)(phth)2(H2O)3]·H2O By journals.iucr.org Published On :: 2024-01-31 A new lanthanide coordination polymer, poly[[triaquabis(μ4-phthalato)(μ3-pyridine-2,5-dicarboxylato)dipraseodymium] monohydrate], {[Pr2(C7H3NO4)2(C8H4O4)(H2O)3]·H2O}n or {[Pr2(phth)2(pydc)(H2O)3]·H2O}n, (pydc2− = pyridine-2,5-dicarboxylate and phth2− = phthalate) was synthesized and characterized, revealing the structure to be an assembly of di-periodic {Pr2(pydc)(phth)2(H2O)3}n layers. Each layer is built up by edge-sharing {Pr2N2O14} and {Pr2O16} dimers, which are connected through a new coordination mode of pydc2− and phth2−. These layers are stabilized by internal hydrogen bonds and π–π interactions. In addition, a three-dimensional supramolecular framework is built by interlayer hydrogen-bonding interactions involving the non-coordinated water molecule. Thermogravimetric analysis shows that the title compound is thermally stable up to 400°C. Full Article text
nation Structural characterization of a new samarium–sodium heterometallic coordination polymer By journals.iucr.org Published On :: 2024-02-06 Lanthanide-containing materials are of interest in the field of crystal engineering because of their unique properties and distinct structure types. In this context, a new samarium–sodium heterometallic coordination polymer, poly[tetrakis(μ2-2-formyl-6-methoxyphenolato)samarium(III)sodium(I)], {[SmNa(C8H7O3)4]·solvent}n (Sm-1), was synthesized and crystallized via slow evaporation from a mixture of ethanol and acetonitrile. The compound features alternating SmIII and NaI ions, which are linked by ortho-vanillin (o-vanillin) ligands to form a mono-periodic chain-like coordination polymer. The chains propagate along the [001] direction. Residual electron density of disordered solvent molecules in the void space could not be reasonably modeled, thus the SQUEEZE function was applied. The structural, vibrational, and optical properties are reported. Full Article text
nation Crystal structure and characterization of a new one-dimensional copper(II) coordination polymer containing a 4-aminobenzoic acid ligand By journals.iucr.org Published On :: 2024-02-20 A CuII coordination polymer, catena-poly[[[aquacopper(II)]-bis(μ-4-aminobenzoato)-κ2N:O;κ2O:N] monohydrate], {[Cu(pABA)2(H2O)]·H2O}n (pABA = p-aminobenzoate, C7H4NO2−), was synthesized and characterized. It exhibits a one-dimensional chain structure extended into a three-dimensional supramolecular assembly through hydrogen bonds and π–π interactions. While the twinned crystal shows a metrically orthorhombic lattice and an apparent space group Pbcm, the true symmetry is monoclinic (space group P2/c), with disordered Cu atoms and mixed roles of water molecules (aqua ligand/crystallization water). The luminescence spectrum of the complex shows an emission at 345 nm, cf. 349 nm for pABAH. Full Article text
nation Synthesis, crystal structure and thermal properties of catena-poly[[bis(4-methylpyridine)nickel(II)]-di-μ-thiocyanato], which shows an alternating all-trans and cis–cis–trans-coordination of the NiS2Np2Nt2 octahedra (p = 4-me By journals.iucr.org Published On :: 2024-06-21 The title compound, [Ni(NCS)2(C6H7N)2]n, was prepared by the reaction of Ni(NCS)2 with 4-methylpyridine in water. Its asymmetric unit consists of two crystallographically independent NiII cations, of which one is located on a twofold rotational axis whereas the second occupies a center of inversion, two independent thiocyanate anions and two independent 4-methylpyridine coligands in general positions. Each NiII cation is octahedrally coordinated by two 4-methylpyridine coligands as well as two N- and two S-bonded thiocyanate anions. One of the cations shows an all-trans, the other a cis–cis–trans configuration. The metal centers are linked by pairs of μ-1,3-bridging thiocyanate anions into [101] chains. X-ray powder diffraction shows that a pure crystalline phase has been obtained and thermogravimetry coupled to differential thermoanalysis reveals that the title compound loses half of the 4-methylpyridine coligands and transforms into Ni(NCS)2(C6H7N). Nearly pure samples of this compound can be obtained by thermal annealing and a Rietveld refinement demonstrated that it is isotypic to its recently reported Cd analog [Neumann et al., (2020). CrystEngComm. 22, 184–194] In its crystal structure, the metal cations are linked by one μ-1,3(N,S)- and one μ-1,3,3(N,S,S)-bridging thiocyanate anion into single chains that condense via the μ-1,3,3(N,S,S)-bridging anionic ligands into double chains. Full Article text