I11-High Resolution Powder Diffraction
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Diamond Proposal Number(s):
[33667]
Open Access
Abstract: The use of conventional zirconium alloys at temperatures above 400 °C is limited by high temperature strength and creep resistance. This has prevented the consideration of zirconium alloys for fusion and Generation IV fission plant designs operating at 500 °C–1000 °C. The physical metallurgy of zirconium is similar to titanium which has seen alloying advances allowing application temperatures up to 600 °C. Although the oxidation resistance of zirconium-based alloys is expected to be poor, in a water environment, new Generation-IV and fusion reactors are designed to operate using alternative coolants such as liquid metals and molten salts. Therefore, a new class of zirconium alloys in the Zr-Al-Sn-(Si,Cr,V) system, designed by analogy to near-
titanium alloys, were synthesised by arc melting and processed in a sequence of homogenisation, hot/cold rolling, recrystallisation, and ageing treatments. Microscopy and diffraction identified a refined fully lath grain structure reinforced by nanoscale lamellar or discrete coherent Zr3Al precipitates, with morphology and crystal structure differing with ageing times. Additionally alloying with Si, Cr, and V respectively leads to Zr2Si, ZrCr2, and ZrV2 incoherent precipitates. Tensile testing revealed a strengthening effect by Al, but with significant changes to ductility on ageing depending on the evolution of Zr3Al. Creep testing showed creep rates orders of magnitude better than conventional Zircaloy-4 and nuclear ferritic/martensitic steels, approaching near-
Ti alloys. The present work offers new insights and perspectives into how high-temperature zirconium alloys might be designed to meet the requirements for fusion and Gen-IV fission.
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Mar 2026
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I04-Macromolecular Crystallography
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Rachel L.
Palte
,
Mihir
Mandal
,
Justyna
Sikorska
,
Artjohn B.
Villafania
,
Meredith M.
Rickard
,
Robert J.
Bauer
,
Alexei V.
Buevich
,
Xiaomei
Chai
,
Jiafang
He
,
Zahid
Hussain
,
Markus
Koglin
,
Hannah B.
Macdonald
,
My S.
Mansueto
,
Klaus
Maskos
,
Joey L.
Methot
,
Jaclyn
Robustelli
,
Aileen
Soriano
,
Marcel J.
Tauchert
,
Sriram
Tyagarajan
,
Minjia
Zhang
,
Daniel J.
Klein
,
Jacqueline D.
Hicks
,
David G.
Mclaren
,
Sandra B.
Gabelli
,
Daniel F.
Wyss
Diamond Proposal Number(s):
[35460]
Open Access
Abstract: WRN helicase is an established synthetic lethal target for inhibition in the treatment of microsatellite instability-high (MSI-H) and mismatch repair deficient (MMRd) cancers. The identification of helicase inhibitors is challenging as high-throughput biochemical screening campaigns typically return few validated hits that are often inactive in cell-based assays. Herein, we highlight the power of non-covalent fragment-based lead discovery in locating new druggable allosteric sites on WRN, enabling us to bypass the challenging behavior of WRN during high-throughput screening hampering hit identification. During the fragment optimization process, structures of WRN with key prioritized fragments reveal multiple conformations of WRN with significant domain rotations up to 180°, including a WRN conformation not previously described. Rooted in a combination of biochemical, biophysical, and structural approaches, we present the detailed analyses of optimized chemical matter evolved from screening hits and the unique ability of WRN to accommodate diverse conformations as detailed by structural characterization.
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Jan 2026
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I04-Macromolecular Crystallography
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Ella K.
Reid
,
Connor G.
Miles
,
Henry O.
Lloyd-Laney
,
Alison K.
Nairn
,
Jessie
Branch
,
Nicholas
Garland
,
Nicholas D. J.
Yates
,
Alex
Ascham
,
Paul H.
Walton
,
Glyn R.
Hemsworth
,
Alison
Parkin
Open Access
Abstract: Lytic polysaccharide monooxygenases ([L]PMOs) are copper-containing enzymes that catalyse cleavage of the glycosidic bond, a process central to microbial biomass degradation. Here, we describe electrochemical methods used to investigate the Cu2+/1+ redox chemistry and the polysaccharide-free catalytic activity of two AA10 LPMOs: CjAA10B from Cellvibrio japonicus and CfAA10 from Cellulomonas fimi. Immobilisation of these enzymes on the surface of a graphite electrode allows for direct electrochemical measurements of Cu2+/1+ redox cycling as well as the ability of both LPMOs to reduce H2O2 vs O2. These measurements can be advantageous when compared to biological dye assays as they provide direct kinetic measurements and allow for investigation over a wider range of environmental conditions. Values of kcat and KM- are reported for H2O2 and O2 reduction by CjAA10B and CfAA10 from pH 5–7, with CfAA10 consistently outperforming CjAA10B. Both enzymes perform faster catalysis with H2O2 but when comparing the affinity-coupled specificity constant (kcat/KM), the LPMOs perform similarly with both H2O2 and O2, suggesting both substrates are viable. We also note an increase in redox signals as pH is decreased that correlates with EPR data suggesting a second species is formed <pH 5, postulated to occur due to the protonation of a glutamate residue (pKa ∼ 4.6). The increase in signal size with decreasing pH that is seen for the non-catalytic Cu2+/1+ transition is interpreted in light of an increasing proportion of electroactive species at low pH; such a change in activity with pH is notably not observed in the presence of substrate (H2O2 or O2). This suggests that substrate binding modulates the active site, disrupting the effect of protonation. These findings establish electrochemistry as a powerful tool for probing LPMO activity.
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Jan 2026
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I11-High Resolution Powder Diffraction
I15-1-X-ray Pair Distribution Function (XPDF)
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Diamond Proposal Number(s):
[32893, 39378]
Open Access
Abstract: Sr2MnO2Cu3.5S3 contains mixed-valent Mn ions Mn2+/3+ in axially elongated MnO4S2 octahedra connected via apical sulfide anions to copper-deficient antifluorite-type Cu4-δS3 layers where δ ∼ 0.5. Copper deficiency is charge-compensated by oxidation of Mn 3d states resulting in mixed-valency. The compound is tetragonal in P4/mmm at ambient temperatures (a = 4.016345(1) Å, c = 11.40708(5) Å). Below 190 K, superlattice reflections in diffraction data and an increase in resistivity, signal checkerboard charge-ordering of Mn2+ and Mn3+. The superstructure approximates to a √2a × √2a × 2c expansion of the room temperature cell in space group P42/nmc. However, satellite reflections signal a (3 + 2)D incommensurate modulation of Cu site occupancies in the Cu-deficient sulfide layers coupled with displacements of the sulfur positions; overall the superstructure below 190 K requires description in superspace group P42/nmc(a,0,0)0000(0,a,0)00s0. Analysis of total scattering measurements along with pair distribution functions supports the charge-ordered low temperature model and reveals local order of distinct Mn sites within the higher-temperature charge-disordered regime. Below TN = 27 K, long-range magnetic ordering is A-type antiferromagnetic with distinct moments for Mn2+ and Mn3+ ions directed perpendicular to the MnO2 planes and ordered ferromagnetically. Long-range antiferromagnetic order results from interlayer antiferromagnetic coupling. A metamagnetic transition at 1.1 T corresponds to a change to long-range interlayer ferromagnetic ordering via a spin-reorientation of magnetic moments and is associated with a slight decrease in the charge separation between the Mn sublattices, consistent with observations on mixed-valent perovskite and Ruddlesden–Popper-type oxide manganites.
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Jan 2026
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I19-Small Molecule Single Crystal Diffraction
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Diamond Proposal Number(s):
[30280]
Open Access
Abstract: Crystalline solvates, including hydrates, hold untapped potential in pharmaceutical development, yet their exploitation remains minimal due to the difficult and laborious task of unequivocally establishing their physical stabilities. We introduce Controlled Solvent-Activity Liquid-Assisted Grinding (CSA-LAG), a mechanochemical protocol that offers solvate phase boundary elucidation by varying the activity of a chosen solvent in defined binary/ternary mixtures and analysing the equilibrated resulting solid form. Using small API amounts, CSA-LAG reaches equilibrium within minutes and yields critical solvent activities that delimit neat, hydrated, solvated and competing-solvate domains. The method uses mixtures of known thermodynamic activities, requires far less material and time than traditional slurries and affords high reproducibility. Applied to four pharmaceutical compounds, CSA-LAG reproduces slurry boundaries and quantifies activity thresholds for single, stepwise and competitive solvations. Defining these boundaries enables rational form selection and process design either by avoiding or targeting solvates, whilst turning a month-scale empirical screening into a rapid, thermodynamically guided workflow.
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Jan 2026
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I19-Small Molecule Single Crystal Diffraction
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Diamond Proposal Number(s):
[35994]
Abstract: Gold catalysis provides access to a remarkable array of complex carbon scaffolds, but the use of silver salts to activate gold(I) chloride precatalysts can be problematic due to Ag(I) light sensitivity, hygroscopicity, redox activity, and interference with the desired catalysis. Although H-bond donors are a promising alternative to silver salts, they still suffer from much lower activity and narrower applicability, as Au–Cl cleavage remains rate limiting. To address these limitations, we have rationally designed a self-activating phosphine Au(I) chloride complex that incorporates a supramolecular chloride receptor in the form of an anthracene bisurea quintuple H-bond donor. In the absence of any additive, this complex promotes multiple intra- and intermolecular reactions, with a catalytic activity rivalling traditional inorganic chloride scavengers. Mechanistic studies for the model reaction show that the exceptional chloride binding ability of the anthracene bisurea unlocks access to a zwitterionic catalyst resting state where the Au─Cl bond has been cleaved, thus significantly reducing barriers for catalysis. The principles uncovered in this work show how supramolecular anion recognition moieties impact catalyst speciation and enhance performance, enabling for the first time H-bond donors to compete with inorganic chloride scavengers in terms of activity and generality.
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Jan 2026
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I24-Microfocus Macromolecular Crystallography
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Diamond Proposal Number(s):
[34223]
Open Access
Abstract: DNA polymerase β (Pol β) is an important polymerase that functions in DNA repair within the Base Excision Repair and Non-Homologous End-Joining pathways. It is estimated to function in the repair of up to 50,000 DNA lesions per cell per day, within the base excision repair pathway (BER). Given the significant role Pol β plays in repairing DNA, genetic variants of Pol β have the potential to perturb repair, resulting in mutation accumulation which can potentiate cancer formation. Here we identify an unstudied human germline variant of Pol β, the S180R variant (rs1585898410), which introduces a significant amino acid alteration within the dNTP binding pocket of the enzyme. We demonstrate that S180R is a low fidelity variant of Pol β due to its loss of the ability to discriminate correct nucleotides from incorrect nucleotides. We also show that this variant exhibits a much slower rate of nucleotide incorporation, which could further disrupt repair capacity in vivo. Structural data reveal that this variant not only has structural changes that may disrupt dNTP binding but also a loss of primer terminus positioning and dynamic flexibility of the fingers domain in the binary state, which likely are driving the low fidelity of S180R Pol β. This study highlights the importance of binary positioning and nucleotide coordinating residues for maintaining nucleotide selectivity, polymerase function, and fidelity. It also emphasizes the importance of further study of this human germline Pol β variant in vivo.
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Jan 2026
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I03-Macromolecular Crystallography
I04-Macromolecular Crystallography
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Diamond Proposal Number(s):
[35324, 26793]
Open Access
Abstract: Fragment-based inhibitor design is an established and widely used approach in drug discovery pipelines. Despite several examples of drugs originating from this approach, the identification of fragments still suffers from issues with solubility, reactivity, cost and worldwide accessibility. Here, we design a low-cost minimal fragment library (LoCoFrag100) for crystallographic screening, with an average cLogP of 0.03 (median 0.23) and an average of £20/g for each compound, facilitating assembly in any laboratory. Formatted in a 10 × 10 matrix to minimize Tanimoto similarity in the 20 cocktails, we demonstrate its applicability on three structurally distinct enzymes involved in microbial cell wall synthesis. Hit rates range from 1 to 6% among these enzymes, with three fragments suggesting avenues for inhibitor exploration.
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Jan 2026
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I24-Microfocus Macromolecular Crystallography
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Lídia Dos Passos
Lima
,
Dev
Sriranganadane
,
Daiane Laise
Da Silva
,
Natália C.
Drebes Dörr
,
Enzo Breviglieri Sichi
Mello
,
Caio Vinicius
Dos Reis
,
Rogério Ferreira
Lourenço
,
José Felipe Teixeira Da Silva
Santos
,
Anita
Salmazo
,
Brenno Wendler
Miranda
,
Katlin B.
Massirer
,
Rafael M.
Counago
,
Cristina E.
Alvarez-Martinez
Open Access
Abstract: Serine/threonine (Ser/Thr) kinases of the Hanks-type family are widespread in bacteria, playing key roles in signal transduction. The transmembrane Ser/Thr kinase PknS (XAC4127) from the phytopathogenic bacterium Xanthomonas citri is required for the expression of a type VI secretion system, which confers resistance to predation by the soil amoeba Dictyostelium discoideum. PknS exerts its function via activation of the cognate ECF-type alternative sigma factor EcfK, ultimately triggering the expression of type VI secretion system (T6SS) genes. In this study, we characterize PknS, demonstrating its ability to undergo autophosphorylation both in vitro and within X. citri cells. Structural analysis of the PknS kinase domain revealed the conservation of the canonical fold characteristic of Hanks-type kinases. PknS directly phosphorylates EcfK at five Ser/Thr residues located in two distinct regions of the sigma factor: the conserved σ2 domain (residue T51) and a nonconserved linker connecting domains σ2 and σ4 (residues T104, T106, S108, and S110). The conserved residue T51, previously shown to be essential for sigma factor activity in an EcfK homolog, corresponds to a site that directly interacts with the RNA polymerase β′ subunit. Site-directed mutagenesis analyses further revealed that the conserved residue T106 is also critical for EcfK function. Structural studies indicated that, in addition to T51, phosphorylation at T106 activates EcfK by promoting its interaction with a positively charged pocket within the RNA polymerase β′ subunit. Collectively, our findings describe a previously unknown signal transduction pathway involving a Hanks-type kinase and a sigma factor, providing new insights into the mechanisms of sigma factor activation via phosphorylation in bacteria.
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Jan 2026
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I03-Macromolecular Crystallography
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Daniel A.
Bonsor
,
Lorenzo I.
Finci
,
Jacob R.
Potter
,
Lucy C.
Young
,
Vanessa E.
Wall
,
Ruby
Goldstein De Salazar
,
Katie R.
Geis
,
Tyler
Stephens
,
Joseph
Finney
,
Dwight V.
Nissley
,
Frank
Mccormick
,
Dhirendra
Simanshu
Open Access
Abstract: RAF activation is essential for MAPK signaling and is mediated by RAS binding and the dephosphorylation of a conserved phosphoserine by the SHOC2–RAS–PP1C complex. MRAS forms a high-affinity SHOC2–MRAS–PP1C (SMP) complex, while canonical RAS isoforms (KRAS, HRAS, NRAS) form analogous but lower-affinity assemblies. Yet, cancers driven by oncogenic KRAS, HRAS, or NRAS remain strongly SHOC2-dependent, suggesting that these weaker complexes contribute to tumorigenesis. To elucidate how canonical RAS proteins form lower-affinity ternary complexes, the cryo-EM structure of the SHOC2–KRAS–PP1C (SKP) complex stabilized by Noonan syndrome mutations is described. The SKP architecture is similar to the SMP complex but forms fewer contacts and buries less surface area due to the absence of MRAS-specific structural features in KRAS that enhance complex stability. RAS inhibitors MRTX1133 and RMC-6236 alter Switch-I/II conformations, thereby blocking SKP assembly more effectively than they disrupt preformed complexes. These RAS inhibitors do not affect SMP formation because they do not bind MRAS. Since MRAS is upregulated in resistance to KRAS inhibition, we characterize a MRAS mutant capable of binding MRTX1133. This MRAS mutant can form an SMP complex, but MRTX1133 blocks its assembly, demonstrating the feasibility of dual SKP and SMP targeting. Overall, our findings define isoform-specific differences in SHOC2–RAS–PP1C complex formation and support a strategy to prevent both SKP and SMP assemblies to overcome resistance in RAS-driven cancers.
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Jan 2026
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