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12,029 items found (0 items not approved), displaying 61 to 70.[First/Prev] 3, 4, 5, 6, 7, 8, 9, 10 [Next/Last]

Instruments / Technical Area	Publication Details	Published
I22-Small angle scattering & Diffraction	Tomographic X-ray scattering based on invariant reconstruction: analysis of the 3D nanostructure of bovine bone Paolino De Falco , Richard Weinkamer , Wolfgang Wagermaier , Chenghao Li , Tim Snow , Nicholas J. Terrill , Himadri Gupta , Pawan Goyal , Martin Stoll , Peter Benner , Peter Fratzl Journal Of Applied Crystallography 54 DOI: 10.1107/S1600576721000881 Diamond Proposal Number(s): [18524] Open Access Show Abstract ▼ Abstract: Small-angle X-ray scattering (SAXS) is an effective characterization technique for multi-phase nanocomposites. The structural complexity and heterogeneity of biological materials require the development of new techniques for the 3D characterization of their hierarchical structures. Emerging SAXS tomographic methods allow reconstruction of the 3D scattering pattern in each voxel but are costly in terms of synchrotron measurement time and computer time. To address this problem, an approach has been developed based on the reconstruction of SAXS invariants to allow for fast 3D characterization of nanostructured inhomogeneous materials. SAXS invariants are scalars replacing the 3D scattering patterns in each voxel, thus simplifying the 6D reconstruction problem to several 3D ones. Standard procedures for tomographic reconstruction can be directly adapted for this problem. The procedure is demonstrated by determining the distribution of the nanometric bone mineral particle thickness (T parameter) throughout a macroscopic 3D volume of bovine cortical bone. The T parameter maps display spatial patterns of particle thickness in fibrolamellar bone units. Spatial correlation between the mineral nanostructure and microscopic features reveals that the mineral particles are particularly thin in the vicinity of vascular channels.	Apr 2021
B22-Multimode InfraRed imaging And Microspectroscopy	Thermal alteration of CM carbonaceous chondrites: Mineralogical changes and metamorphic temperatures A. J. King , P. J. Schofield , S. S. Russell Geochimica Et Cosmochimica Acta 298, 167 - 190 DOI: 10.1016/j.gca.2021.02.011 Diamond Proposal Number(s): [9614, 18213] Show Abstract ▼ Abstract: The CM carbonaceous chondrite meteorites provide a record of low temperature (<150 °C) aqueous reactions in the early solar system. A number of CM chondrites also experienced short-lived, post-hydration thermal metamorphism at temperatures of ∼200 °C to >750 °C. The exact conditions of thermal metamorphism and the relationship between the unheated and heated CM chondrites are not well constrained but are crucial to understanding the formation and evolution of hydrous asteroids. Here we have used position-sensitive-detector X-ray diffraction (PSD-XRD), thermogravimetric analysis (TGA) and transmission infrared (IR) spectroscopy to characterise the mineralogy and water contents of 14 heated CM and ungrouped carbonaceous chondrites. We show that heated CM chondrites underwent the same degree of aqueous alteration as the unheated CMs, however upon thermal metamorphism their mineralogy initially (300–500 °C) changed from hydrated phyllosilicates to a dehydrated amorphous phyllosilicate phase. At higher temperatures (>500 °C) we observe recrystallisation of olivine and Fe-sulphides and the formation of metal. Thermal metamorphism also caused the water contents of heated CM chondrites to decrease from ∼13 wt% to ∼3 wt% and a subsequent reduction in the intensity of the 3 μm feature in IR spectra. We estimate that the heated CM chondrites have lost ∼15 - >65% of the water they contained at the end of aqueous alteration. If impacts were the main cause of metamorphism, this is consistent with shock pressures of ∼20–50 GPa. However, not all heated CM chondrites retain shock features suggesting that some were instead heated by solar radiation. Evidence from the Hayabusa2 and ORSIRS-REx missions suggest that dehydrated materials may be common on the surfaces of primitive asteroids and our results will support upcoming analysis of samples returned from asteroids Ryugu and Bennu.	Apr 2021
Krios I-Titan Krios I at Diamond Krios II-Titan Krios II at Diamond Krios III-Titan Krios III at Diamond	CryoET structures of immature HIV Gag reveal six-helix bundle Luiza Mendonca , Dapeng Sun , Jiying Ning , Jiwei Liu , Abhay Kotecha , Mateusz Olek , Thomas Frosio , Xiaofeng Fu , Benjamin A. Himes , Alex B. Kleinpeter , Eric O. Freed , Jing Zhou , Christopher Aiken , Peijun Zhang Communications Biology 4 DOI: 10.1038/s42003-021-01999-1 Diamond Proposal Number(s): [18477, 21005, 21004] Open Access Show Abstract ▼ Abstract: Gag is the HIV structural precursor protein which is cleaved by viral protease to produce mature infectious viruses. Gag is a polyprotein composed of MA (matrix), CA (capsid), SP1, NC (nucleocapsid), SP2 and p6 domains. SP1, together with the last eight residues of CA, have been hypothesized to form a six-helix bundle responsible for the higher-order multimerization of Gag necessary for HIV particle assembly. However, the structure of the complete six-helix bundle has been elusive. Here, we determined the structures of both Gag in vitro assemblies and Gag viral-like particles (VLPs) to 4.2 Å and 4.5 Å resolutions using cryo-electron tomography and subtomogram averaging by emClarity. A single amino acid mutation (T8I) in SP1 stabilizes the six-helix bundle, allowing to discern the entire CA-SP1 helix connecting to the NC domain. These structures provide a blueprint for future development of small molecule inhibitors that can lock SP1 in a stable helical conformation, interfere with virus maturation, and thus block HIV-1 infection.	Apr 2021
I04-Macromolecular Crystallography	Structural basis of prolyl hydroxylase domain inhibition by molidustat William D. Figg , Michael A. Mcdonough , Rasheduzzaman Chowdhury , Yu Nakashima , Zhihong Zhang , James P. Holt‐martyn , Alen Krajnc , Christopher J. Schofield Chemmedchem 5 DOI: 10.1002/cmdc.202100133 Diamond Proposal Number(s): [18069] Open Access Show Abstract ▼ Abstract: Human prolyl‐hydroxylases (PHDs) are hypoxia‐sensing 2‐oxoglutarate (2OG) oxygenases, catalysis by which suppresses the transcription of hypoxia‐inducible factor target genes. PHD inhibition enables the treatment of anaemia/ischaemia‐related disease. The PHD inhibitor Molidustat is approved for the treatment of renal anaemia; it differs from other approved/late‐stage PHD inhibitors in lacking a glycinamide side chain. The first reported crystal structures of Molidustat and IOX4 (a brain‐penetrating derivative) complexed with PHD2 reveal how their contiguous triazole, pyrazolone and pyrimidine/pyridine rings bind at the active site. The inhibitors bind to the active‐site metal in a bidentate manner through their pyrazolone and pyrimidine nitrogens, with the triazole π‐π‐stacking with Tyr303 in the 2OG binding pocket. Comparison of the new structures with other PHD inhibitor complexes reveals differences in the conformations of Tyr303, Tyr310, and a mobile loop linking β2–β3, which are involved in dynamic substrate binding/product release.	Apr 2021
	Ce=O terminated CeO2 David Charles Grinter , Michael Allan , Hyun Jin Yang , Agustín Salcedo , Gustavo E. Murgida , Bobbie-Jean Shaw , Chi L. Pang , Hicham Idriss , M. Verónica Ganduglia-Pirovano , Geoff Thornton Angewandte Chemie International Edition DOI: 10.1002/anie.202101771 Open Access Show Abstract ▼ Abstract: Multiply‐bonded lanthanide oxo groups are rare in coordination compounds and have not previously been reported for a surface termination of a lanthanide oxide. Here we report the observation of a Ce=O terminated ceria surface in a CeO 2 (111)‐( [[EQUATION]] x [[EQUATION]] )R30° reconstruction of ~3 nm thick ceria islands prepared on Pt(111). This is evidenced by scanning tunnelling microscopy, low energy electron diffraction and high‐resolution electron energy loss spectroscopy (HREELS) measurements in conjunction with density functional theory (DFT) calculations. A Ce=O stretching frequency of 775 cm ‐1 is observed in HREELS, compared with 766 cm ‐1 calculated by DFT. The calculations also predict that the Ce=O bond is weak, with an oxygen vacancy formation energy of 0.85 eV. This could play an important role in the facile removal of lattice oxygen from CeO 2 , accompanied by the reduction of Ce IV to Ce III , which is a key attribute of ceria‐based systems in connection with their unique catalytic properties.	Apr 2021
I12-JEEP: Joint Engineering, Environmental and Processing	Evaluation of fracture toughness and residual stress in AISI 316L electron beam welds Mehdi Mokhtarishirazabad , Chris Simpson , Saurabh Kabra , Graeme Horne , Iain Palmer , Andrew Moffat , Christopher Truman , David Knowles , Mahmoud Mostafavi Fatigue & Fracture Of Engineering Materials & Structures 21 DOI: 10.1111/ffe.13472 Diamond Proposal Number(s): [21780] Show Abstract ▼ Abstract: Weld residual stress and fracture behavior of 316L electron beam weldments, which are of particular interest in power generation industry, were investigated in this work. Two butt‐weld joints were manufactured in stainless steel 316L plates of 6 mm and 25.4 mm thicknesses. Three complementary methods were used to measure the three orthogonal components of the residual stress in the weld coupons, and fracture tests were conducted on single edge notched bending specimens extracted from different regions of the welds and parent metals. The residual stress measurements showed a maximum value of 450 MPa in longitudinal direction, while it was less than 150 MPa in the other two orthogonal directions, revealing that in our material, and with the chosen weld parameters, the residual stresses were biaxial. The fracture resistance of the weldment and parent material was similar, with material microstructure differences being more significant than the measured residual stresses. The study suggests that 316L electron beam weldments are not susceptible to fracture failure due to their high ductility and ability to relieve residual stresses through gross plasticity. Electron beam welding may therefore be suggested as a reliable manufacturing technology for safety critical 316L components.	Apr 2021
B23-Circular Dichroism	CD imaging at high spatial resolution at Diamond B23 beamline: Evolution and applications Rohanah Hussain , Tamas Javorfi , Giuliano Siligardi Frontiers In Chemistry 9 DOI: 10.3389/fchem.2021.616928 Diamond Proposal Number(s): [26447] Open Access Show Abstract ▼ Abstract: Circular Dichroism imaging in the 190–650 nm spectral region pionered at Diamond Light Source B23 beamline, has been made possible by the highly collimated microbeam generated at the beamline and has been used to study the homogeneity of the supramolecular structures of thin films of chiral materials deposited on fused quartz substrates. This facility has been expanded with the installation of a Mueller Matrix Polarimeter, MMP, coupled to the beamlight, of which a preliminary data will be discussed. In the solid state, the measurement of CD related to the supramolecular structure is hampered by the presence of circular birefringence, linear dichroism, and linear birefringence that can only be evaluated using the MMP technique. The ability to characterize the chiroptical property of thin chiral films prepared under a variety of conditions and protocols such as drop cast, spin coating, spray at different temperatures and concentrations will enable the determination of the critical parameters for reproducible, uniform and homogeneous specimen preparation, which is the sine qua non for any commercial application. This is of particular importance for optoelectronic materials, but it can also be extended to a broad variety of materials with applications from biosensors to biological tissues.	Apr 2021
I07-Surface & interface diffraction	A two‐dimensional polyimide‐graphene heterostructure with ultra‐fast interlayer charge transfer Kejun Liu , Jiang Li , Haoyuan Qi , Mike Hambsch , Jonathan Rawle , Adrián Romaní Vázquez , Ali Shaygan Nia , Alexej Pashkin , Harald Schneider , Mirosllav Polozij , Thomas Heine , Manfred Helm , Stefan C. B. Mannsfeld , Ute Kaiser , Renhao Dong , Xinliang Feng Angewandte Chemie International Edition DOI: 10.1002/anie.202102984 Diamond Proposal Number(s): [25070] Show Abstract ▼ Abstract: Two‐dimensional polymers (2DPs) are a class of atomically/molecularly thin crystalline organic 2D materials. They are intriguing candidates for the development of unprecedented organic‐inorganic 2D van der Waals heterostructures (vdWHs) with exotic physicochemical properties. In this work, we demonstrate the on‐water surface synthesis of large‐area (cm 2 ), monolayer 2D polyimide (2DPI) with 3.1‐nm lattice. Such 2DPI comprises metal‐free porphyrin and perylene units linked by imide bonds. We further achieve a scalable synthesis of 2DPI‐graphene (2DPI‐G) vdWHs via a face‐to‐face co‐assembly of graphene and 2DPI on the water surface. Remarkably, femtosecond transient absorption spectroscopy reveals an ultra‐fast interlayer charge transfer (~60 fs) in the resultant 2DPI‐G vdWH upon protonation by acid, which is equivalent to that of the fastest reports among inorganic 2D vdWHs. Such large interlayer electronic coupling is ascribed to the interlayer cation‐π interaction between 2DP and graphene. Our work opens opportunities to develop 2DP‐based vdWHs via the on‐water surface synthesis strategy and highlights the unique interface‐induced optoelectronic properties.	Apr 2021
	Vagabond : bond-based parametrization reduces overfitting for refinement of proteins Helen M. Ginn Acta Crystallographica Section D Structural Biology 77 DOI: 10.1107/S2059798321000826 Open Access Show Abstract ▼ Abstract: Structural biology methods have delivered over 150 000 high-resolution structures of macromolecules, which have fundamentally altered our understanding of biology and our approach to developing new medicines. However, the description of molecular flexibility is instrinsically flawed and in almost all cases, regardless of the experimental method used for structure determination, there remains a strong overfitting bias during molecular model building and refinement. In the worst case this can lead to wholly incorrect structures and thus incorrect biological interpretations. Here, by reparametrizing the description of these complex structures in terms of bonds rather than atomic positions, and by modelling flexibility using a deterministic ensemble of structures, it is demonstrated that structures can be described using fewer parameters than in conventional refinement. The current implementation, applied to X-ray diffraction data, significantly reduces the extent of overfitting, allowing the experimental data to reveal more biological information in electron-density maps.	Apr 2021
I15-1-X-ray Pair Distribution Function (XPDF)	Generating the atomic pair distribution function without instrument or emission profile contributions Alan A. Coelho , Philip A. Chater , Michael J. Evans Journal Of Applied Crystallography 54, 444 - 453 DOI: 10.1107/S1600576721000765 Show Abstract ▼ Abstract: A method for generating the atomic pair distribution function (PDF) from powder diffraction data by the removal of instrument contributions, such as Kα2 from laboratory instruments or peak asymmetry from neutron time-of-flight data, has been implemented in the computer programs TOPAS and TOPAS-Academic. The resulting PDF is sharper, making it easier to identify structural parameters. The method fits peaks to the reciprocal-space diffraction pattern data whilst maximizing the intensity of a background function. The fit to the raw data is made `perfect' by including a peak at each data point of the diffraction pattern. Peak shapes are not changed during refinement and the process is a slight modification of the deconvolution procedure of Coelho [J. Appl. Cryst. (2018[Coelho, A. A. (2018a). J. Appl. Cryst. 51, 112-123.]), 51, 112–123]. Fitting to the raw data and subsequently using the calculated pattern as an estimation of the underlying signal reduces the effects of division by small numbers during atomic scattering factor and polarization corrections. If the peak shape is sufficiently accurate then the fitting process should also be able to determine the background if the background intensity is maximized; the resulting calculated pattern minus background should then comprise coherent scattering from the sample. Importantly, the background is not allowed complete freedom; instead, it comprises a scan of an empty capillary sample holder with a maximum of two additional parameters to vary its shape. Since this coherent scattering is a calculated pattern, it can be easily recalculated without instrumental aberrations such as capillary sample aberration or Kα2 from laboratory emission profiles. Additionally, data reduction anomalies such as incorrect integration of data from two-dimensional detectors, resulting in peak position errors, can be easily corrected. Multiplicative corrections such as polarization and atomic scattering factors are also performed. Once corrected, the pattern can be scaled to produce the total scattering structure factor F(Q) and from there the sine transform is applied to obtain the pair distribution function G(r).	Apr 2021

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