I21-Resonant Inelastic X-ray Scattering (RIXS)
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Open Access
Abstract: A photon carrying one unit of angular momentum can change the spin angular momentum of a magnetic system with one unit (ΔMs = ±1) at most. This implies that a two-photon scattering process can manipulate the spin angular momentum of the magnetic system with a maximum of two units. Herein we describe a triple-magnon excitation in α-Fe2O3, which contradicts this conventional wisdom that only 1- and 2-magnon excitations are possible in a resonant inelastic X-ray scattering experiment. We observe an excitation at exactly three times the magnon energy, along with additional excitations at four and five times the magnon energy, suggesting quadruple and quintuple-magnons as well. Guided by theoretical calculations, we reveal how a two-photon scattering process can create exotic higher-rank magnons and the relevance of these quasiparticles for magnon-based applications.
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May 2023
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I03-Macromolecular Crystallography
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Diamond Proposal Number(s):
[24948]
Open Access
Abstract: We report a chemo-biocatalytic cascade for the synthesis of substituted pyrroles, driven by the action of an irreversible, thermostable, pyridoxal 5′-phosphate (PLP)-dependent, C–C bond-forming biocatalyst (ThAOS). The ThAOS catalyzes the Claisen-like condensation between various amino acids and acyl-CoA substrates to generate a range of α-aminoketones. These products are reacted with β-keto esters in an irreversible Knorr pyrrole reaction. The determination of the 1.6 Å resolution crystal structure of the PLP-bound form of ThAOS lays the foundation for future engineering and directed evolution. This report establishes the AOS family as useful and versatile C–C bond-forming biocatalysts.
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May 2023
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Krios II-Titan Krios II at Diamond
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Diamond Proposal Number(s):
[25452]
Open Access
Abstract: Phages are viruses that infect bacteria and dominate every ecosystem on our planet. As well as impacting microbial ecology, physiology and evolution, phages are exploited as tools in molecular biology and biotechnology. This is particularly true for the Ff (f1, fd or M13) phages, which represent a widely distributed group of filamentous viruses. Over nearly five decades, Ffs have seen an extraordinary range of applications, yet the complete structure of the phage capsid and consequently the mechanisms of infection and assembly remain largely mysterious. In this work, we use cryo-electron microscopy and a highly efficient system for production of short Ff-derived nanorods to determine a structure of a filamentous virus including the tips. We show that structure combined with mutagenesis can identify phage domains that are important in bacterial attack and for release of new progeny, allowing new models to be proposed for the phage lifecycle.
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May 2023
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B21-High Throughput SAXS
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Biswanath
Hansda
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Jhilam
Majumder
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Biplab
Mondal
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Akash
Chatterjee
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Subhadeep
Das
,
Sourav
Kumar
,
Ratan
Gachhui
,
Valeria
Castelletto
,
Ian W.
Hamley
,
Prosenjit
Sen
,
Arindam
Banerjee
Diamond Proposal Number(s):
[29895]
Abstract: A histidine-based amphiphilic peptide (P) has been found to form an injectable transparent hydrogel in phosphate buffer solution over a pH range from 7.0 to 8.5 with an inherent antibacterial property. It also formed a hydrogel in water at pH = 6.7. The peptide self-assembles into a nanofibrillar network structure which is characterized by high-resolution transmission electron microscopy, field-emission scanning electron microscopy, atomic force microscopy, small-angle X-ray scattering, Fourier-transform infrared spectroscopy, and wide-angle powder X-ray diffraction. The hydrogel exhibits efficient antibacterial activity against both Gram-positive bacteria Staphylococcus aureus (S. aureus) and Gram-negative bacteria Escherichia coli (E. coli). The minimum inhibitory concentration of the hydrogel ranges from 20 to 100 μg/mL. The hydrogel is capable of encapsulation of the drugs naproxen (a non-steroidal anti-inflammatory drug), amoxicillin (an antibiotic), and doxorubicin, (an anticancer drug), but, selectively and sustainably, the gel releases naproxen, 84% being released in 84 h and amoxicillin was released more or less in same manner with that of the naproxen. The hydrogel is biocompatible with HEK 293T cells as well as NIH (mouse fibroblast cell line) cells and thus has potential as a potent antibacterial and drug releasing agent. Another remarkable feature of this hydrogel is its magnification property like a convex lens.
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May 2023
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I15-1-X-ray Pair Distribution Function (XPDF)
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Open Access
Abstract: Membranes with ultrahigh permeance and practical selectivity could greatly decrease the cost of difficult industrial gas separations, such as CH4/N2 separation. Advanced membranes made from porous materials, such as metal–organic frameworks, can achieve a good gas separation performance, although they are typically formed on support layers or mixed with polymeric matrices, placing limitations on gas permeance. Here an amorphous glass foam, agfZIF-62, wherein a, g and f denote amorphous, glass and foam, respectively, was synthesized by a polymer-thermal-decomposition-assisted melting strategy, starting from a crystalline zeolitic imidazolate framework, ZIF-62. The thermal decomposition of incorporated low-molecular-weight polyethyleneimine evolves CO2, NH3 and H2O gases, creating a large number and variety of pores. This greatly increases pore interconnectivity but maintains the crystalline ZIF-62 ultramicropores, allowing ultrahigh gas permeance and good selectivity. A self-supported circular agfZIF-62 with a thickness of 200–330 µm and area of 8.55 cm2 was used for membrane separation. The membranes perform well, showing a CH4 permeance of 30,000–50,000 gas permeance units, approximately two orders of magnitude higher than that of other reported membranes, with good CH4/N2 selectivity (4–6).
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May 2023
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Y.
Liu
,
D. M.
Sanchez
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M. R.
Ware
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E. G.
Champenois
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J.
Yang
,
J. P. F.
Nunes
,
A.
Attar
,
M.
Centurion
,
J. P.
Cryan
,
R.
Forbes
,
K.
Hegazy
,
M. C.
Hoffmann
,
F.
Ji
,
M.-F.
Lin
,
D.
Luo
,
S. K.
Saha
,
X.
Shen
,
X. J.
Wang
,
T. J.
Martínez
,
T. J. A.
Wolf
Open Access
Abstract: Electrocyclic reactions are characterized by the concerted formation and cleavage of both σ and π bonds through a cyclic structure. This structure is known as a pericyclic transition state for thermal reactions and a pericyclic minimum in the excited state for photochemical reactions. However, the structure of the pericyclic geometry has yet to be observed experimentally. We use a combination of ultrafast electron diffraction and excited state wavepacket simulations to image structural dynamics through the pericyclic minimum of a photochemical electrocyclic ring-opening reaction in the molecule α-terpinene. The structural motion into the pericyclic minimum is dominated by rehybridization of two carbon atoms, which is required for the transformation from two to three conjugated π bonds. The σ bond dissociation largely happens after internal conversion from the pericyclic minimum to the electronic ground state. These findings may be transferrable to electrocyclic reactions in general.
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May 2023
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B18-Core EXAFS
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Nicola
Schiaroli
,
Leila
Negahdar
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Mads
Lützen
,
Phuoc
Hoang Ho
,
Lisa J.
Allen
,
Alejandro
Natoli
,
Francesca
Ospitali
,
Francesco
Maluta
,
Enrique
Rodríguez-Castellón
,
Christian D.
Damsgaard
,
Giuseppe
Fornasari
,
Andrew M.
Beale
,
Patricia
Benito
Abstract: Pd-In2O3 catalysts are among the most promising alternatives to Cu-ZnO-Al2O3 for synthesis of CH3OH from CO2. However, the intrinsic activity and stability of In2O3 per unit mass should be increased to reduce the content of this scarcely available element and to enhance the catalyst lifetime. Herein, we propose and demonstrate a strategy for obtaining highly dispersed Pd and In2O3 nanoparticles onto an Al2O3 matrix by a one-step coprecipitation followed by calcination and activation. The activity of this catalyst is comparable with that of a Pd-In2O3 catalyst (0.52 vs. 0.55 gMeOH h-1 gcat-1 at 300°C, 30 bar, 40,800 ml h-1 gcat-1) but the In2O3 loading decreases from 98 to 12 wt.% while improving the long-term stability by three-fold at 30 bar. In the new Pd-In2O3-Al2O3 system, the intrinsic activity of In2O3 is highly increased both in terms of STY normalized to In specific surface area and In2O3 mass (4.32 vs 0.56 g gMeOH h-1 gIn2O3-1 of a Pd- In2O3 catalyst operating at 300°C, 30 bar, 40,800 ml h-1 gcat-1).The combination of ex situ and in situ catalyst characterizations during reduction provides insights into the interaction between Pd and In and with the support. The enhanced activity is likely related to the close proximity of Pd and In2O3, wherein the H2 splitting activity of Pd promotes, in combination with CO2 activation over highly dispersed In2O3 particles, facile formation of CH3OH.
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May 2023
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I24-Microfocus Macromolecular Crystallography
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Diamond Proposal Number(s):
[19951]
Open Access
Abstract: Facultative anaerobic bacteria such as Escherichia coli have two α2β2 heterotetrameric trifunctional enzymes (TFE), catalyzing the last three steps of the β-oxidation cycle: soluble aerobic TFE (EcTFE) and membrane-associated anaerobic TFE (anEcTFE), closely related to the human mitochondrial TFE (HsTFE). The cryo-EM structure of anEcTFE and crystal structures of anEcTFE-α show that the overall assembly of anEcTFE and HsTFE is similar. However, their membrane-binding properties differ considerably. The shorter A5-H7 and H8 regions of anEcTFE-α result in weaker α-β as well as α-membrane interactions, respectively. The protruding H-H region of anEcTFE-β is therefore more critical for membrane-association. Mutational studies also show that this region is important for the stability of the anEcTFE-β dimer and anEcTFE heterotetramer. The fatty acyl tail binding tunnel of the anEcTFE-α hydratase domain, as in HsTFE-α, is wider than in EcTFE-α, accommodating longer fatty acyl tails, in good agreement with their respective substrate specificities.
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May 2023
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I09-Surface and Interface Structural Analysis
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Maria
Basso
,
Elena
Colusso
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Chiara
Carraro
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Curran
Kalha
,
Aysha A.
Riaz
,
Giada
Bombardelli
,
Enrico
Napolitani
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Yu
Chen
,
Jacek
Jasieniak
,
Laura E.
Ratcliff
,
Pardeep K.
Thakur
,
Tien-Lin
Lee
,
Anna
Regoutz
,
Alessandro
Martucci
Diamond Proposal Number(s):
[29451]
Abstract: The thermochromic properties of vanadium dioxide (VO2) offer great advantages for energy-saving smart windows, memory devices, and transistors. However, the crystallization of solution-based thin films at temperatures lower than 400°C remains a challenge. Photonic annealing has recently been exploited to crystallize metal oxides, with minimal thermal damage to the substrate and reduced manufacturing time. Here, VO2 thin films, obtained via a green sol-gel process, were crystallized by pulsed excimer laser annealing. The influence of increasing laser fluence and pulse number on the film properties was systematically studied through optical, structural, morphological, and chemical characterizations. From temperature profile simulations, the temperature rise was confirmed to be confined within the film during the laser pulses, with negligible substrate heating. Threshold laser parameters to induce VO2 crystallization without surface melting were found. With respect to furnace annealing, both the crystallization temperature and the annealing time were substantially reduced, with VO2 crystallization being achieved within only 60 s of laser exposure. The laser processing was performed at room temperature in air, without the need of a controlled atmosphere. The thermochromic properties of the lasered thin films were comparable with the reference furnace-treated samples.
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May 2023
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I22-Small angle scattering & Diffraction
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Abstract: In this thesis, we report the ability to fabricate hydrogels using low molecular weight gelators (LMWGs) and the subsequent characterisation of their mechanical properties over a variety of different length scales. These materials have been investigated due to their potential use in a wide range of biomedical applications including drug delivery, tissue engineering, cell culture and wound healing.
We describe the localised gelation of LMWGs on electrode surfaces via electrochemically generated pH gradients. The electrofabrication of hydrogels on electrode surfaces has shown great potential in the field of biomedicine, with applications ranging from antimicrobial wound dressings, tissue engineering scaffolds and biomimetic materials.
First, we describe the largest reported di- and tri-peptide-based hydrogels on electrode surfaces via the electrochemical oxidation of hydroquinone. Expanding upon previous work which focuses on the fabrication of hydrogels on the nanometre to millimetre scale, we deposit hydrogels around 3 cm3 in size. Furthermore, we demonstrate that there is an upper limit to how large the hydrogels can grow which is determined by the size of the pH gradient from the electrode surface. To grow hydrogels of this size, much longer deposition times of two to five hours are required than in previous reports. When the gelator/hydroquinone solution is left exposed to the open atmosphere for this amount of time, the hydroquinone in solution oxidises to benzoquinone/quinhydrone before it can be consumed electrochemically. This inhibits the electrochemical reaction and reduces gelation efficiency. To prevent this, we build a system that can perform the fabrication process under an inert nitrogen atmosphere. Using this system, we show how the choice of gelator affects the mechanical properties of the hydrogel and the resulting material phenomena that cause these changes. As well as this, we show how this approach can be used to grow multi-layered hydrogels, with each layer presenting different chemical and mechanical properties.
Secondly, we report the first known example of electrodeposition for a LMWG molecule using an electrochemically generated basic pH gradient at electrode surfaces. This approach has previously been used to fabricate hydrogels of the biopolymer chitosan using the galvanostatic reduction of hydrogen peroxide. During the electrochemical reduction of hydrogen peroxide, hydroxide ions are produced. As a result, a basic pH zone is generated at the electrode, triggering solutions of chitosan to form immobilised hydrogels on the electrode surface. Using this approach, we show how electrodeposition at high pH can be applied to our LMWG system.
We then show that we can electrochemically form hydrogels at high pH, with the gel properties being greatly improved by the addition and increased concentration of hydrogen peroxide. Following from this, we then show the simultaneous formation of two low molecular weight hydrogels at acidic and basic pH extremes. To achieve this, we couple the electrochemical reduction of hydrogen peroxide and the electrochemical oxidation of hydroquinone described in the previous chapter.
Finally, we report the electrodeposition of five carbazole-protected amino acid hydrogels on electrode surfaces via the electrochemical oxidation of hydroquinone. As well as this, we report the full to partial electropolymerisation of the pre-assembled hydrogels in perchloric acid. For the less bulky carbazole-protected amino acids, the full collapse of the hydrogel to form electrochromic polymers on the electrode surface is achieved. However, for the bulkier gelators, little to no evidence of polymerisation occurs. We believe this is due to the bulky side chain on the gelator backbone preventing the molecular reorganization required for polymerization to occur.
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May 2023
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