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9,950 items found (0 items not approved), displaying 1 to 10.[First/Prev] 1, 2, 3, 4, 5, 6, 7, 8 [Next/Last]

Instruments / Technical Area	Publication Details	Published
I12-JEEP: Joint Engineering, Environmental and Processing	Measurement of strain evolution in overloaded roller bearings using energy dispersive X-ray diffraction A. Reid , C. Simpson , I. Martinez , S. Kabra , T. Connolley , O. Magdysyuk , C. Charlesworth , M. Marshall , M. Mostafavi Tribology International 140 DOI: 10.1016/j.triboint.2019.105893 Diamond Proposal Number(s): [18468] Open Access Show Abstract ▼ Abstract: There are several mechanisms contributing towards detrimental damage in wind turbine gearbox bearings, with sudden overload events believed to reduce their expected operational life. The generation of subsurface plasticity, followed by rolling contact fatigue, may lead to the initiation of either surface or subsurface cracking. This study presents a novel technique capable of measuring subsurface strain evolution in a rotating roller bearing, using energy dispersive X-ray diffraction. A pre-overloaded bearing was tested dynamically and consequently failed prematurely, supporting the hypothesis that overloads accelerate bearing failure. Throughout the test, an increase in compressive radial strain was observed, indicative of material softening, generally associated with the unstable stage of rolling contact fatigue, which occurs prior to definitive bearing failure.	Dec 2019
I11-High Resolution Powder Diffraction	Synthesis and ion exchange properties of zirconogermanates Ryan George , Joseph A. Hriljac Mrs Advances 4, 965 - 970 DOI: 10.1557/adv.2018.639 Diamond Proposal Number(s): [18206] Show Abstract ▼ Abstract: Pure and Nb-doped zirconium germanate materials of composition K2-xZr1-xNbxGe3O9.H2O where x = 0, 0.1, 0.2 and 0.25 with the structure of the mineral umbite have been successfully synthesised. The parent material displays negligible ion exchange of K+ for Cs+ but the doped materials shows much improved exchange. Synchrotron X-ray diffraction shows substantial peak splitting which varies with increasing niobium content. Preliminary Rietveld refinements suggest a two phase model with a caesium and potassium rich doped umbite phase.	Dec 2019
I15-Extreme Conditions	Temperature-induced atomic structural evolution in a liquid Ga-based alloy Mengwan Li , Yongjiang Huang , Peng Xue , Songshan Jiang , Weinan Ru , Zhiqin Yang , Hangboce Yin , Dominik Daisenberger , Hongxian Shen , Jianfei Sun Vacuum 170 DOI: 10.1016/j.vacuum.2019.108966 Diamond Proposal Number(s): [9902, 8858, 17412] Show Abstract ▼ Abstract: The atomic-scale structural evolution of Ga68.5In21·5Sn10 (wt. %) liquid alloy has been explored utilizing in-situ high-energy synchrotron X-ray diffraction from room temperature (293 K) to around the melting point. During the process of decreasing temperature, bond lengths of dominant atomic pairs decrease, whereas the total coordination numbers of the first nearest neighbor shell increase. This structural transition is ascribed to the redistribution of atoms and/or clusters and the decrease of vacancies induced by decreasing temperature. Our results are supportive for further understanding the atomic-scale structural evolution of liquid alloys at the low-temperature condition.	Dec 2019
I12-JEEP: Joint Engineering, Environmental and Processing	A simultaneous X-ray diffraction–differential scanning calorimetry study into the phase transitions of mefenamic acid Yuying Pang , Asma Buanz , Richard Telford , Oxana V. Magdysyuk , Simon Gaisford , Gareth Williams Journal Of Applied Crystallography 52 DOI: 10.1107/S1600576719012500 Diamond Proposal Number(s): [187201] Show Abstract ▼ Abstract: In this study, the polymorphic transitions of mefenamic acid (MA) were studied by synchrotron X-ray powder diffraction combined with differential scanning calorimetry (XRD-DSC). The initial material was found to be phase-pure form I which, when heated, produces two endotherms that can be observed by DSC at 162.72 and 219.55°C. The former was found to correspond to a solid–solid enantiotropic transition from form I to a mixture of forms II and III. The latter is the melting point of form II. As form I is heated, significantly greater unit-cell expansion is seen in the a direction than in b and c, which can be explained by the stronger intermolecular interactions in the bc plane. Refinements of the reported MA structures against the patterns collected during heating revealed that at 175°C there exists a mixture of forms I, II and III, whereas only forms II and III remain at 205°C. However, reflections are observed at both temperatures which cannot be fitted with the known forms of MA. It is hypothesized that a new form of MA is produced upon heating. The stability of MA after the enantiotropic transition temperature is II > III > I, which differs from the previously reported II > I > III.	Dec 2019
I18-Microfocus Spectroscopy	Mantle plumes are oxidised Yves Moussallam , Marc-antoine Longpré , Catherine Mccammon , Alejandra Gomez-ulla , Estelle F. Rose-koga , Bruno Scaillet , Nial Peters , Emanuela Gennaro , Raphael Paris , Clive Oppenheimer Earth And Planetary Science Letters 527 DOI: 10.1016/j.epsl.2019.115798 Diamond Proposal Number(s): [17250] Show Abstract ▼ Abstract: From oxic atmosphere to metallic core, the Earth's components are broadly stratified with respect to oxygen fugacity. A simple picture of reducing oxygen fugacity with depth may be disrupted by the accumulation of oxidised crustal material in the deep lower mantle, entrained there as a result of subduction. While hotspot volcanoes are fed by regions of the mantle likely to have incorporated such recycled material, the oxygen fugacity of erupted hotspot basalts had long been considered comparable to or slightly more oxidised than that of mid-ocean ridge basalt (MORB) and more reduced than subduction zone basalts. Here we report measurements of the redox state of glassy crystal-hosted melt inclusions from tephra and quenched lava samples from the Canary and Cape Verde Islands, that we can independently show were entrapped prior to extensive sulphur degassing. We find high ferric iron to total iron ratios (Fe3+/∑Fe) of up to 0.27–0.30, indicating that mantle plume primary melts are significantly more oxidised than those associated with mid-ocean ridges and even subduction zone. These results, together with previous investigations from the Erebus, Hawaiian and Icelandic hotspots, confirm that mantle upwelling provides a return flow from the deep Earth for components of oxidised subducted lithosphere and suggest that highly oxidised material accumulates or is generated in the lower mantle. The oxidation state of the Earth's interior must therefore be highly heterogeneous and potentially locally inversely stratified.	Dec 2019
I07-Surface & interface diffraction	In−situ monitoring Poly(3-hexylthiophene) nanowire formation and shape evolution in solution via small angle neutron scattering Francesco Bastianini , Gabriel E. Pérez , Adam R. Hobson , Sarah E. Rogers , Andrew J. Parnell , Martin Grell , Alfredo Flores Gutiérrez , Alan D. F. Dunbar Solar Energy Materials And Solar Cells 202 DOI: 10.1016/j.solmat.2019.110128 Diamond Proposal Number(s): [8117] Show Abstract ▼ Abstract: The crystallization of poly(3-hexylthiophene) (P3HT) to form nanowires has attracted considerable interest because this process significantly increases the hole mobility when compared to amorphous P3HT, leading to improved performance in photovoltaic and other organic electronic devices. However, full characterization of the crystallization self-assembly of the polymer chains in solution has not been achieved yet, due to limited use of in−situ not destructive techniques. Here, we investigate the ageing-driven formation and evolution of regioregular (rr) P3HT nanostructures in chlorobenzene solution using small angle neutron scattering (SANS) and UV–Vis spectroscopy. We have monitored how the shape of the rr-P3HT aggregates evolves. The initial states for rr-P3HT chains are the random coils, which straighten to form rods. These subsequently π - π stack to form 2D lamellae, which further stack to create nanowires. The formation of nanowires is promoted both by the length of ageing and by low temperatures ( 4∘C ). Temperatures above >40∘C reverse the formation of nanowires. Additionally, atomic force microscopy (AFM) and grazing incidence wide angle x-ray scattering (GIWAXS) reveal that the nanowires can be successfully aligned during deposition by off-axis spin coating. Finally, the anisotropic conductivity of the aligned rr-P3HT nanowire films is reported. This is significant for applications such as gas sensing or organic thin film transistors, where increased conductivity and controlled nanostructure are desirable.	Nov 2019
I03-Macromolecular Crystallography I04-Macromolecular Crystallography	Crystal structure of the putative cyclase IdmH from the indanomycin nonribosomal peptide synthase/polyketide synthase Ieva Drulyte , Jana Obajdin , Chi H. Trinh , Arnout P. Kalverda , Marc W. Van Der Kamp , Glyn R. Hemsworth , Alan Berry Iucrj 6 DOI: 10.1107/S2052252519012399 Diamond Proposal Number(s): [15378] Open Access Show Abstract ▼ Abstract: Indanomycin is biosynthesized by a hybrid nonribosomal peptide synthase/polyketide synthase (NRPS/PKS) followed by a number of `tailoring' steps to form the two ring systems that are present in the mature product. It had previously been hypothesized that the indane ring of indanomycin was formed by the action of IdmH using a Diels–Alder reaction. Here, the crystal structure of a selenomethionine-labelled truncated form of IdmH (IdmH-Δ99–107) was solved using single-wavelength anomalous dispersion (SAD) phasing. This truncated variant allows consistent and easy crystallization, but importantly the structure was used as a search model in molecular replacement, allowing the full-length IdmH structure to be determined to 2.7 Å resolution. IdmH is a homodimer, with the individual protomers consisting of an α+β barrel. Each protomer contains a deep hydrophobic pocket which is proposed to constitute the active site of the enzyme. To investigate the reaction catalysed by IdmH, 88% of the backbone NMR resonances were assigned, and using chemical shift perturbation of [15N]-labelled IdmH it was demonstrated that indanomycin binds in the active-site pocket. Finally, combined quantum mechanical/molecular mechanical (QM/MM) modelling of the IdmH reaction shows that the active site of the enzyme provides an appropriate environment to promote indane-ring formation, supporting the assignment of IdmH as the key Diels–Alderase catalysing the final step in the biosynthesis of indanomycin through a similar mechanism to other recently characterized Diels–Alderases involved in polyketide-tailoring reactions. An animated Interactive 3D Complement (I3DC) is available in Proteopedia at https://proteopedia.org/w/Journal:IUCrJ:S2052252519012399.	Nov 2019
	High-throughput structures of protein–ligand complexes at room temperature using serial femtosecond crystallography Tadeo Moreno Chicano , Ali Ebrahim , Danny Axford , Martin V. Appleby , John H. Beale , Amanda K. Chaplin , Helen M. E. Duyvesteyn , Reza A. Ghiladi , Shigeki Owada , Darren A. Sherrell , Richard Strange , Hiroshi Sugimoto , Kensuke Tono , Jonathan A. R. Worrall , Robin L. Owen , Michael A. Hough Iucrj 6 DOI: 10.1107/S2052252519011655 Open Access Show Abstract ▼ Abstract: High-throughput X-ray crystal structures of protein–ligand complexes are critical to pharmaceutical drug development. However, cryocooling of crystals and X-ray radiation damage may distort the observed ligand binding. Serial femtosecond crystallography (SFX) using X-ray free-electron lasers (XFELs) can produce radiation-damage-free room-temperature structures. Ligand-binding studies using SFX have received only modest attention, partly owing to limited beamtime availability and the large quantity of sample that is required per structure determination. Here, a high-throughput approach to determine room-temperature damage-free structures with excellent sample and time efficiency is demonstrated, allowing complexes to be characterized rapidly and without prohibitive sample requirements. This yields high-quality difference density maps allowing unambiguous ligand placement. Crucially, it is demonstrated that ligands similar in size or smaller than those used in fragment-based drug design may be clearly identified in data sets obtained from <1000 diffraction images. This efficiency in both sample and XFEL beamtime opens the door to true high-throughput screening of protein–ligand complexes using SFX.	Nov 2019
I02-Macromolecular Crystallography	Structure-function relationships underlying the dual N-acetylmuramic and N-acetylglucosamine specificities of the bacterial peptidoglycan deacetylase PdaC Laia Grifoll-romero , Maria Angela Sainz-polo , David Albesa-jove , Marcelo Guerin , Xevi Biarnés , Antoni Planas Journal Of Biological Chemistry DOI: 10.1074/jbc.RA119.009510 Diamond Proposal Number(s): [15304] Show Abstract ▼ Abstract: Bacillus subtilis PdaC (BsPdaC) is a membrane-bound, multidomain peptidoglycan N-deacetylase acting on N-acetylmuramic (Mur-NAc) residues and conferring lysozyme resistance to modified cell wall peptidoglycans. BsPdaC contains a C-terminal family 4 carbohydrate esterase (CE4) catalytic domain, but unlike other MurNAc deacetylases, BsPdaC also has GlcNAc deacetylase activity on chitooligosaccharides (COSs), characteristic of chitin deacetylases. To uncover the molecular basis of this dual activity, here we determined the X-ray structure of the BsPdaC CE4 domain at 1.54 Å resolution and analyzed its mode of action on COS substrates. We found that the minimal substrate is GlcNAc3 and that activity increases with the degree of glycan polymerization. COS deacetylation kinetics revealed that BsPdaC operates by a multiple-chain mechanism starting at the internal GlcNAc units and leading to deacetylation of all but the reducing-end GlcNAc residues. Interestingly, BsPdaC shares higher sequence similarity with the peptidoglycan GlcNAc deacetylase SpPgdaA than with other MurNAc deacetylases. Therefore, we used ligand-docking simulations to analyze the dual GlcNAc- and MurNAc-binding specificities of BsPdaC and compared them with those of SpPgdA and BsPdaA, representing peptidoglycan deacetylases highly specific for GlcNAc or MurNAc residues, respectively. BsPdaC retains the conserved Asp–His–His metal-binding triad characteristic of CE4 enzymes acting on GlcNAc residues, differing from MurNAc deacetylases that lack the metal-coordinating Asp residue. BsPdaC contains short loops similar to those in SpPgdA, resulting in an open binding cleft that can accommodate polymeric substrates. We propose that PdaC is the first member of a new subclass of peptidoglycan MurNAc deacetylases.	Nov 2019
I03-Macromolecular Crystallography I04-1-Macromolecular Crystallography (fixed wavelength)	Crystal structure of the catalytic D2 domain of the AAA + ATPase p97 reveals a putative helical split‐washer‐type mechanism for substrate unfolding Lasse Stach , R. Marc Morgan , Linda Makhlouf , Alice Douangamath , Frank Von Delft , Xiaodong Zhang , Paul S. Freemont Febs Letters DOI: 10.1002/1873-3468.13667 Diamond Proposal Number(s): [16980] Show Abstract ▼ Abstract: Several pathologies have been associated with the AAA + ATPase p97, an enzyme essential to protein homeostasis. Heterozygous polymorphisms in p97 have been shown to cause neurological disease, while elevated proteotoxic stress in tumours has made p97 an attractive cancer chemotherapy target. The cellular processes reliant on p97 are well described. High‐resolution structural models of its catalytic D2 domain, however, have proved elusive, as has the mechanism by which p97 converts the energy from ATP hydrolysis into mechanical force to unfold protein substrates. Here, we describe the high‐resolution structure of the p97 D2 ATPase domain. This crystal system constitutes a valuable tool for p97 inhibitor development and identifies a potentially druggable pocket in the D2 domain. In addition, its P61 symmetry suggests a mechanism for substrate unfolding by p97.	Nov 2019

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