I11-High Resolution Powder Diffraction
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Open Access
Abstract: A family of seven silver(I)-perfluorocarboxylate-quinoxaline coordination polymers, [Ag 4 (O 2 CR F ) 4 (quin) 4 ] 1 - 5 (R F = (CF 2 ) n-1 CF 3 ) 4 , n = 1 to 5); [Ag 4 (O 2 C(CF 2 ) 2 CO 2 ) 2 (quin) 4 ] 6 ; [Ag 4 (O 2 CC 6 F 5 ) 4 (quin) 4 ] 7 (quin = quinoxaline), denoted by composition as 4:4:4 phases , was synthesised from reaction of the corresponding silver(I) perfluorocarboxylate with excess quinoxaline. Compounds 1 - 7 adopt a common 2D layered structure in which 1D silver-perfluorcarboxylate chains are crosslinked by ditopic quinoxaline ligands. Solid-state reaction upon heating, involving loss of one equivalent of quinoxaline, yielding new crystalline 4:4:3 phases [Ag 4 (O 2 C(CF 2 ) n-1 CF 3 ) 4 (quin) 3 ] n ( 8 - 10 , n = 1 to 3), was followed in situ by PXRD and TGA studies. Crystal structures were confirmed by direct syntheses and structure determination. The solid-state reaction converting 4:4:4 to 4:4:3 phase materials involves cleavage and formation of Ag–N and Ag–O bonds to enable the structural rearrangement. One of the 4:4:3 phase coordination polymers ( 10 ) shows the remarkably high dielectric constant in the low electric field frequency range.
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Jun 2022
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I11-High Resolution Powder Diffraction
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Shanshan
Liu
,
Yinlin
Chen
,
Bin
Yue
,
Chang
Wang
,
Bin
Qin
,
Yuchao
Chai
,
Guangjun
Wu
,
Jiangnan
Li
,
Xue
Han
,
Ivan
Da Silva
,
Pascal
Manuel
,
Sarah J.
Day
,
Naijia
Guan
,
Stephen P.
Thompson
,
Sihai
Yang
,
Landong
Li
Diamond Proposal Number(s):
[29649]
Abstract: The development of cost-effective sorbents for direct capture of trace CO 2 (<1%) from the atmosphere is an important and challenging task. Natural or commercial zeolites are promising sorbents, but their performance in adsorption of trace CO 2 has been poorly explored to date. Herein, we report a systematic study on capture of trace CO 2 by commercial faujasite zeolites, where we found that the extra-framework cations played a key role on their performance. Under dry conditions, Ba-X displays high dynamic uptake of 1.79 and 0.69 mmol g -1 at CO 2 concentrations of 10000 and 1000 ppm, respectively, and shows excellent recyclability in the temperature-swing adsorption processes. K-X exhibits perfect moisture resistance, and >95 % dry CO 2 uptake can be preserved under relative humidity of 74%. In situ solid-state NMR spectroscopy, synchrotron X-ray diffraction and neutron diffraction reveal two binding sites for CO 2 in these zeolites, namely the basic framework oxygen atoms and the divalent alkaline earth metal ions. This study unlocks the potential of low-cost natural zeolites for applications in direct air capture.
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Jun 2022
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I19-Small Molecule Single Crystal Diffraction
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Diamond Proposal Number(s):
[22411]
Abstract: Extremely high electrophilic metal complexes, composed by a metal cation and very electron poor σ–donor ancillary ligands, are expected to be privileged catalysts for oxidation reactions in organic chemistry. However, their low lifetime prevents any use in catalysis. Here we show the synthesis of fluorinated pyridine–Pd 2+ coordinate cages within the channels of an anionic tridimensional metal organic framework (MOF), and their use as efficient metal catalysts for the aerobic oxidation of aliphatic alcohols to carboxylic acids without any additive. Mechanistic studies strongly support that the MOF–stabilized coordination cage with perfluorinated ligands unleashes the full electrophilic potential of Pd 2+ to dehydrogenate primary alcohols, without any base, and also to activate O 2 for the radical oxidation to the aldehyde intermediate. This study opens the door to design catalytic perfluorinated complexes for challenging organic transformations, where an extremely high electrophilic metal site is required.
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Dec 2021
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B23-Circular Dichroism
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Diamond Proposal Number(s):
[17621, 19225]
Abstract: Solid-state ECD (ss-ECD) spectra of a model microcrystalline solid, finasteride, dispersed into a KCl pellet were recorded by using the synchrotron radiation source at the Diamond B23 beamline. Scanning a surface of 36 mm2 with a step of 0.5 mm, we measured a set of ECD imaging (ECDi) spectra very different from each other and from the ss-ECD recorded with a bench-top instrument (1 cm2 area). This is due to the anisotropic part of the ECD (ACD), which averages to zero in solution or on a large number of randomly oriented crystallites, but can otherwise be extremely large. Two-way singular value decomposition (SVD) analysis, through experimental and simulated TDDFT spectra, disclosed that the measured and theoretical principal components are in line with each other. This finding demonstrates that the observed isotropic ss-ECD spectrum is governed by the anisotropy of locally oriented crystals. It also introduces a new quality for ss-ECD measurements and opens a new future for probing and mapping chiral materials in the solid state such as active pharmaceutical ingredients (APIs).
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Dec 2021
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I03-Macromolecular Crystallography
I04-1-Macromolecular Crystallography (fixed wavelength)
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David J.
Fallon
,
Stephanie
Lehmann
,
Chun‐wa
Chung
,
Alex
Phillipou
,
Christian
Eberl
,
Ken G. M.
Fantom
,
Francesca
Zappacosta
,
Vipulkumar K.
Patel
,
Marcus
Bantscheff
,
Christopher J.
Schofield
,
Nicholas C. O.
Tomkinson
,
Jacob T.
Bush
Diamond Proposal Number(s):
[20024]
Abstract: We present a one-step Ugi reaction protocol for the expedient synthesis of photoaffinity probes for live-cell MS-based proteomics. The reaction couples an amine affinity function with commonly used photoreactive groups, and a variety of handle functionalities. Using this technology, a series of pan-BET (BET: bromodomain and extra-terminal domain) selective bromodomain photoaffinity probes were obtained by parallel synthesis. Studies on the effects of photoreactive group, linker length and irradiation wavelength on photocrosslinking efficiency provide valuable insights into photoaffinity probe design. Optimal probes were progressed to MS-based proteomics to capture the BET family of proteins from live cells and reveal their potential on- and off-target profiles.
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Sep 2021
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I02-Macromolecular Crystallography
I03-Macromolecular Crystallography
I04-Macromolecular Crystallography
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Gideon J.
Davies
,
Rhianna J.
Rowland
,
Yurong
Chen
,
Imogen
Breen
,
Liang
Wu
,
Wendy A.
Offen
,
Thomas
Beenakker
,
Qin
Su
,
Adrianus M. C. H.
Van Den Nieuwendijk
,
Johannes M. F. G.
Aerts
,
Marta
Artola
,
Herman S.
Overkleeft
Diamond Proposal Number(s):
[13587, 18598]
Abstract: Gaucher disease (GD) is a lysosomal storage disorder caused by inherited deficiencies in β-glucocerebrosidase (GBA). Current treatments require rapid disease diagnosis and a means of monitoring therapeutic efficacy, both of which may be supported by the use of GBA-targeting activity-based probes (ABPs). Here, we report the synthesis and structural analysis of a range of cyclophellitol epoxide and aziridine inhibitors and ABPs for GBA. We demonstrate their covalent mechanism-based mode of action and uncover binding of the new N- functionalised aziridines to the ligand binding cleft. These inhibitors became scaffolds for the development of ABPs; the O6-fluorescent tags of which bind in an allosteric site at the dimer interface. Considering GBA’s preference for O6- and N -functionalised reagents, we synthesised a bi-functional aziridine ABP which we hoped would offer a more powerful imaging agent. Whilst this ABP binds to two unique active site clefts of GBA, no further benefit in potency was achieved over our first generation ABPs. Nevertheless, such ABPs should serve useful in the study of GBA in relation to GD and inform the design of future probes.
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Sep 2021
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I03-Macromolecular Crystallography
I04-Macromolecular Crystallography
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Abstract: Ferritins are nanocage proteins that store iron ions in their central cavity as hydrated ferric oxide biominerals. In mammals, further the L (light) and H (heavy) chains constituting cytoplasmic maxi-ferritins, an additional type of ferritin has been identified, the mitochondrial ferritin (MTF). Human MTF (hMTF) is a functional homopolymeric H-like ferritin performing the ferroxidase activity in its ferroxidase site (FS), in which Fe(II) is oxidized to Fe(III) in the presence of dioxygen. To better investigate its ferroxidase properties, here we performed time-lapse X-ray crystallography analysis of hMTF, providing structural evidence of how iron ions interact with hMTF and of their binding to the FS. Transient iron binding sites, populating the pathway along the cage from the iron entry channel to the catalytic center, were also identified. Furthermore, our kinetic data at variable iron loads indicate that the catalytic iron oxidation reaction occurs via a diferric peroxo intermediate followed by the formation of ferric-oxo species, with significant differences with respect to human H-type ferritin.
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Aug 2021
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I19-Small Molecule Single Crystal Diffraction
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Diamond Proposal Number(s):
[18953]
Open Access
Abstract: Determining the relative configuration or enantiomeric excess of a substance may be achieved using NMR spectroscopy by employing chiral shift reagents (CSRs). Such reagents non-covalently interact with the chiral solute, resulting in each chiral form experiencing different magnetic anisotropy, which is reflected in their NMR spectra. The Keplerate polyoxometalate (POM) is a molybdenum-based, water-soluble, discrete inorganic structure with a pore-accessible inner cavity, decorated by differentiable ligands. Through ligand exchange from the self-assembled nanostructure we have synthesized a set of chiral Keplerate host molecules. By exploiting interactions of analyte molecules at the surface pores we establish the relative configuration of chiral amino alcohol guests (phenylalaninol and 2-amino-1-phenylethanol) in aqueous solvent and determine their enantiomeric excess by 1 H NMR. The use of POMs as chiral shift reagents represents an application of the class that is yet to be well established and opens avenues into aqueous host-guest chemistry with self-assembled recognition agents.
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Jul 2021
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I11-High Resolution Powder Diffraction
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Diamond Proposal Number(s):
[22322]
Abstract: The flexibility of the zeolite Rho framework offers great potential for tunable molecular sieving. The fully copper-exchanged form of Rho and mixed Cu,H- and Cu,Na-forms have been prepared. EPR spectroscopy reveals Cu 2+ cations are present in the dehydrated forms and Rietveld refinement shows these prefer S6R sites, away from the d8r windows that control diffusion. Fully exchanged Cu-Rho remains in an open form upon dehydration, the d8r windows remain nearly circular and the occupancy of window sites is low, so that it adsorbs CO 2 rapidly at room temperature. Breakthrough tests with 10% CO 2 /40% CH 4 mixtures show that Cu 4.9 -Rho is able to produce pure methane, albeit with a relatively low capacity at this p CO2 due to the weak interaction of CO 2 with Cu cations. This is in strong contrast with Na-Rho, where cations in narrow elliptical window sites enable CO 2 to be adsorbed with high selectivity and uptake but too slowly to enable the production of pure methane in similar breakthrough experiments. A series of Cu,Na-Rho materials was prepared to improve uptake and selectivity compared to Cu-Rho, and kinetics compared to Na-Rho. Remarkably, Cu,Na-Rho with >2 Cu cations per unit cell exhibited exsolution, due to the preference of Na cations for narrow S8R sites in distorted Rho and of Cu cations for S6R sites in the centric, open form of Rho. The exsolved Cu,Na-Rho showed improved performance in CO 2 /CH 4 breakthrough tests, producing pure CH 4 with improved uptake and CO 2 /CH 4 selectivity compared to that of Cu 4.9 -Rho.
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Jul 2021
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I15-1-X-ray Pair Distribution Function (XPDF)
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Diamond Proposal Number(s):
[12102]
Abstract: Amorphous TixOy with high surface area has attracted significant interest as photocatalyst with higher activity in ultraviolet (UV) light-induced water splitting applications compared to commercial nanocrystalline TiO2. Under photocatalytic operation conditions, the structure of the molecular titanium alkoxide precursor rearranges upon hydrolysis and leads to higher connectivity of the structure-building units. Structurally ordered domains with sizes smaller than 7 Å form larger aggregates. The experimental scattering data can be explained best with a structure model consisting of an anatase-like core and a distorted shell. Upon exposure with UV light, the white TixOy suspension turns dark corresponding to the reduction of Ti 4+ to Ti 3+ as confirmed by electron energy loss spectroscopy (EELS). Heat-induced crystallisation was followed by in situ temperature-dependent total scattering experiments. First, ordering in the Ti-O environment takes place upon to 350 °C. Above this temperature, the distorted anatase core starts to grow but the structure obtained at 400 °C is still not fully ordered.
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Jun 2021
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