I18-Microfocus Spectroscopy
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Diamond Proposal Number(s):
[34311]
Abstract: Rice is a staple food for over half the world's population. This study uniquely investigates the spatial distribution of key micronutrients (Cu, Mn, Fe, Zn) in cooked brown, white, and parboiled rice using Synchrotron Micro-X-ray Fluorescence (sXRF) for the first time. Complementary analysis with Inductively Coupled Plasma Mass Spectrometry (ICP-MS) validates bulk elemental concentrations. Results from this dual-approach study reveal significantly higher micronutrient concentrations in brown rice compared to white or parboiled rice, with nutrients predominantly localised in the peripheral layers and minimal presence in the endosperm. Notably, sXRF imaging identified nutrient-rich pockets within the grain periphery, offering new perspectives on nutrient distribution beyond peripheral accumulation. Additional insights include the impact of rice section thickness (50 and 150 μm) and beam dwell times (0.5 and 30s) on sXRF sensitivity and resolution, highlighting trade-offs in detection capabilities, advancing our understanding of micronutrient localisation in cooked rice.
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Dec 2025
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B18-Core EXAFS
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Diamond Proposal Number(s):
[34446]
Open Access
Abstract: Understanding the redox behavior and structural stability of aliovalent substituents in ionic conductors is critical, as their variable oxidation states can inadvertently introduce electronic conductivity and alter transport mechanisms under different atmospheric conditions. Here, we report the atmosphere-dependent redox behavior and local coordination of Mo in LaNb0.9Mo0.1O4.05, focusing on its influence on phase transition and transport properties, where the as-sintered LaNb0.9Mo0.1O4.05 was systematically annealed under pure O2, pure N2, vacuum (∼1.6 × 10–8 mbar), and 5% H2/N2 at 800 °C for different dwell times. Electron paramagnetic resonance (EPR) spectroscopy results demonstrate the emergence of Mo5+ under 5% H2/N2. In situ X-ray absorption near edge structure (XANES) measurements reveal the reversible redox behavior of Mo, where Mo5+ formed under 5% H2/N2 reoxidizes to Mo6+ upon exposure to static air, while complementary in situ extended X-ray absorption fine structure (EXAFS) analysis shows that the Nb coordination environment also transitions from prototypical LaNbO4 structure under reducing conditions back to the Mo-substituted LaNbO4 structure upon reoxidation. This change of the oxidation states of Mo could correspondingly alter the band structure of the sample, which further enhances charge transport: the sample annealed in 5% H2/N2 for 24 h exhibits a reduced activation energy and increased electronic conductivity. These results highlight a strong coupling among substituent redox flexibility, local structure, and transport properties, providing an understanding of tailoring the properties of ionic conductors through controlled redox environments.
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Dec 2025
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I04-1-Macromolecular Crystallography (fixed wavelength)
I24-Microfocus Macromolecular Crystallography
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Diamond Proposal Number(s):
[25108, 18565]
Open Access
Abstract: The accessory secretion (aSec) system is a protein export pathway that is uniquely present in Gram-positive bacteria and is dedicated to the secretion of large, glycosylated cell wall-anchored adhesins called serine-rich repeat proteins (SRRPs). Strain-specific glycosylation of SRRPs has previously been reported in Limosilactobacillus reuteri and attributed to GtfC, a glycosyltransferase belonging to family 113, with LrGtfC100-23 from L. reuteri rat strain 100-23C showing specificity for UDP-Glc, while LrGtfC53608 from L. reuteri pig strain ATCC 53608, which differs at only ten amino-acid positions, shows a preference for UDP-GlcNAc. However, the structural basis underpinning GtfC sugar-donor specificity remains unclear. Here, we report X-ray crystal structures of the tetrameric LrGtfC100-23 in the apo form and its complexes with UDP and with the noncognate sugar donor UDP-N-acetylglucosamine (UDP-GlcNAc). Analysis of the LrGtfC100-23 structures identified candidate residues implicated in donor-sugar substrate specificity, which were supported by site-directed mutagenesis. Reciprocal swaps of candidate residues combined with thermal shift assays revealed that the W240C variant of LrGtfC100–23 could bind both UDP-sugar donors, while the P243S variant of LrGtfC53608 became specific for UDP-Glc, opening the door for glycoengineering approaches in bacteria.
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Dec 2025
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B07-B1-Versatile Soft X-ray beamline: High Throughput ES1
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Diamond Proposal Number(s):
[34919, 37955]
Open Access
Abstract: A combination of experimental methods and computational techniques have been used to investigate the composition of the zinc ferrite (ZnFe2O4) (1 1 1) single crystal surface under different preparation methods. Surface-sensitive XPS and NEXAFS measurements show that upon annealing in ultra-high vacuum (UHV), Zn depletion occurs, leading to the formation of an iron-rich (1 1 1) surface, whereas annealing in the presence of O2 gas maintains a more bulk-like ZnFe2O4 surface composition. Analysis of the Fe 2p photoemission (XPS) and Fe L edge X-ray absorption signals shows a clear difference in iron oxidation state and distribution between the two different preparation conditions. After annealing in UHV, a mixed Fe2+/Fe3+ oxidation state and a cation distribution like that of a magnetite (Fe3O4) structure is observed, whereas after annealing in oxygen gas only Fe3+, mostly in octahedral coordination, is observed, as expected for a ZnFe2O4 structure. Temperature-dependent XPS confirms significant Zn depletion in the near-surface region above 500 °C under UHV, with almost no Zn remaining at 600 °C; under an O2 atmosphere no zinc depletion is observed up to 600 °C. A theoretical model based on DFT simulations illustrates how reduction from ZnFe2O4 to Fe3O4 with formation of O2 and Zn gas is thermodynamically feasible under UHV conditions, whereas the same reaction is not favourable at higher oxygen partial pressures. Our findings demonstrate the strong impact that UHV treatment has on zinc ferrite surfaces, and cautions that UHV environments, routinely employed for surface analysis, can themselves induce substantial modifications to the surface, thereby complicating the interpretation of measurements in the context of catalytically relevant conditions.
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Dec 2025
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B18-Core EXAFS
I18-Microfocus Spectroscopy
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Diamond Proposal Number(s):
[33674, 35117, 35776, 40942]
Open Access
Abstract: Metal–organic frameworks (MOFs) are entering water technologies on the premise that abiotic stability predicts ecological safety. We overturn this assumption by showing that UiO-66 – often regarded as chemically and structurally robust – remains intact after 7-day aging in natural borehole water yet undergoes rapid in vivo transformation in Daphnia magna. Synchrotron Microfocus X-ray absorption spectroscopy (XAS) revealed collapse of the ordered Zr–carboxylate coordination into disordered Zr–O environments within the gut; Extended X-ray Absorption Fine Structure (EXAFS) showed loss of second-shell features, and Transmission Electron Microscopy (TEM) confirmed loss of crystallinity with nanoscale aggregates appearing within 24 h of ingestion. Although acute immobilization was limited (48 h EC50 ≈ 26.5 μg mL–1), a sublethal, environmentally relevant exposure (10 μg mL–1) caused pronounced chronic effects: brood initiation was delayed by 3–5 days and cumulative reproduction decreased by ∼74% without mortality. We attribute these outcomes to gut-level transformation and associated energetic/physiological burdens, not captured by standard acute tests. These results show that abiotic stability does not necessarily imply biological inertness and highlight the need to integrate in vivo transformation pathways with chronic end points in environmental risk assessment for water-sector materials. This perspective provides a mechanistic basis to inform Safe-and-Sustainable-by-Design (SSbD) MOFs before widespread deployment in water treatment.
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Dec 2025
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I22-Small angle scattering & Diffraction
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Open Access
Abstract: A liquid crystal (LC) polymethylsiloxane (PMS) with rod-like aromatic side-groups attached via an alkylene spacer and bearing three n-dodecyl end-tails is found to form an unusual cubic structure. In a normal LC double gyroid (DG), the two chiral subspaces, one each side of the G-surface, are occupied by one network each. Here each such network is split into two aromatic strands that wind around the central polysiloxane bundle, forming a double helix, resulting in a four-network gyroid (4NG). While in previous normal LC DGs the network twist was assumed to follow that of the subspace, in 4NG the twist sense of the double-helix is opposite to that of the subspace., i.e., while a right-handed subspace twists by +70.5° between junctions, the double-helix “supertwists” by −109.5°, and the opposite is true for the left-handed subspace. Detailed analysis by X-ray diffraction, DSC, and depolarized fluorescence (DF) shows a gradual but significant reversible change in the degree of mixing between the aromatic side groups and the polysiloxane backbones at 120 °C–130 °C in 4NG. Also, a significant increase in the system mobility starts only at ∼40 °C above the melting point, indicating persistence of local double-helical segments even in the melt.
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Dec 2025
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Abstract: The low-temperature performance of mixed-composition perovskite solar cells (PSCs) reflects the complex interplay among thermal effects, bandgap renormalization, and structural phase behavior. Temperature-dependent structural, optical, and electrical measurements reveal a maximum power conversion efficiency at 263 K, which coincides with the onset of the cubic-tetragonal phase coexistence. At this temperature, symmetry lowering is observed, accompanied by a split emission band and increased current–voltage hysteresis, consistent with structural heterogeneity. Device simulations show that any benefit from mixed-phase band alignment is conditional on effective interphase passivation. Consequently, the mixed phase is best described as a loss-minimum condition at well-passivated cubic–tetragonal interphases with stable collection. Our findings identify a narrow mixed-phase window in which phase coexistence couples to the optoelectronic response and enhances the device performance, providing fundamental insight into temperature-dependent structure–property relations in hybrid perovskites.
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Dec 2025
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I24-Microfocus Macromolecular Crystallography
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Francesca
Coscia
,
Ioannis
Riziotis
,
Antonina
Andreeva
,
Delhi
Kalwan
,
Jennifer
De Jong
,
Philip
Hinchliffe
,
Fabio
Parmeggiani
,
Paul R.
Race
,
Steven G.
Burston
,
Alex
Bateman
,
Rob
Barringer
Diamond Proposal Number(s):
[31440]
Open Access
Abstract: Many proteins harbor covalent intramolecular bonds that enhance their stability and resistance to thermal, mechanical, and proteolytic insults. Intramolecular isopeptide bonds represent one such covalent interaction, yet their distribution across protein domains and organisms has been largely unexplored. Here, we sought to address this by employing a large-scale prediction of intramolecular isopeptide bonds in the AlphaFold database using the structural template-based software Isopeptor. Our findings reveal an extensive phyletic distribution in bacterial and archaeal surface proteins resembling fibrillar adhesins and pilins. All identified intramolecular isopeptide bonds are found in two structurally distinct folds, CnaA-like or CnaB-like, from a relatively small set of related Pfam families, including 10 novel families that we predict to contain intramolecular isopeptide bonds. One CnaA-like domain of unknown function, DUF11 (renamed here to “CLIPPER”) is broadly distributed in cell-surface proteins from Gram-positive bacteria, Gram-negative bacteria, and archaea, and is structurally and biophysically characterized in this work. Using x-ray crystallography, we resolve a CLIPPER domain from a Gram-negative fibrillar adhesin that contains an intramolecular isopeptide bond and further demonstrate that it imparts thermostability and resistance to proteolysis. Our findings demonstrate the extensive distribution of intramolecular isopeptide bond-containing protein domains in nature and structurally resolve the previously cryptic CLIPPER domain.
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Dec 2025
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B18-Core EXAFS
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Diamond Proposal Number(s):
[29950]
Open Access
Abstract: Aims: To investigate the phase changes of bismuth oxide in contact with sodium hypochlorite responsible for tooth discolouration. Methodology: Bismuth oxide (monoclinic α−phase; C) was mixed with sodium hypochlorite at 20°C, 37°C, and 60°C (B20, B37, B60) for a period of 24 weeks with weekly refreshing of solutions. The products were imaged by scanning electron and optical microscopy and characterized by thermographic analysis (TGA), phase analysis by X-ray diffraction (XRD) using Bragg Brentano geometry and Pilatus detector, infrared spectroscopy (FT-IR), and X-ray absorption fine structure (XAFS). Results: The interaction of bismuth oxide with sodium hypochlorite resulted in a change in microstructure and colour. The thermographic assessment showed a change in mass (5%–10% weight change) and colour reversal to the yellow bismuth oxide at ~450°C. Phase changes dependent on temperature were demonstrated with δ-bismuth oxide, sodium bismuthate and bismuth oxychloride formed as by-products at the different temperatures. Conclusions: The δ-phase bismuth oxide formation led to the material darkening which will cause tooth discolouration in a clinical setting. Due to the phase changes, the material chemistry after the interaction is different from that of the material placed in the tooth. The by-products of the reaction have not been tested for use in patients. It is recommended to ban the use of bismuth oxide from dental materials and other clinical use due to its instability. The clinical guidance for endodontic treatment needs to be changed to reflect this.
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Dec 2025
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B21-High Throughput SAXS
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Sung Ryul
Choi
,
Thorsten B.
Blum
,
Matteo
Giono
,
Bibhas
Roy
,
Ioannis
Vakonakis
,
Dominic
Schmid
,
Nicole
Oelgarth
,
Apisha
Ranganathan
,
Alvar D.
Gossert
,
G. V.
Shivashankar
,
Alfred
Zippelius
,
Michel O.
Steinmetz
Open Access
Abstract: Microtubules have long been recognized as upstream mediators of intracellular signaling, but the mechanisms underlying this fundamental function remain elusive. Here, we identify the structural basis by which microtubules regulate the guanine nucleotide exchange factor H1 (GEFH1), a key activator of the Ras homolog family member A (RhoA) pathway. We show that specific features of the microtubule lattice bind the C1 domain of GEFH1, leading to the sequestration and inactivation of this signaling protein. Targeted mutations in C1 residues disrupt this interaction, triggering GEFH1 release and activation of RhoA-dependent immune responses. Building on this sequestration-and-release mechanism, we identify microtubule-binding C1 domains in additional signaling proteins, including other guanine nucleotide exchange factors (GEFs), kinases, a GTPase-activating protein (GAP), and a tumor suppressor, and show that microtubule-mediated regulation via C1 domains is conserved in the Ras association domain-containing protein 1A (RASSF1A). Our findings establish a structural framework for understanding how microtubules can function as spatiotemporal signal sensors, integrating and processing diverse signaling pathways to control important cellular processes.
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Dec 2025
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