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1.
Nat Commun ; 15(1): 267, 2024 Jan 24.
Article in English | MEDLINE | ID: mdl-38267429

ABSTRACT

Ultrafast photoinduced phase transitions at room temperature, driven by a single laser shot and persisting long after stimuli, represent emerging routes for ultrafast control over materials' properties. Time-resolved studies provide fundamental mechanistic insight into far-from-equilibrium electronic and structural dynamics. Here we study the photoinduced phase transformation of the Rb0.94Mn0.94Co0.06[Fe(CN)6]0.98 material, designed to exhibit a 75 K wide thermal hysteresis around room temperature between MnIIIFeII tetragonal and MnIIFeIII cubic phases. We developed a specific powder sample streaming technique to monitor by ultrafast X-ray diffraction the structural and symmetry changes. We show that the photoinduced polarons expand the lattice, while the tetragonal-to-cubic photoinduced phase transition occurs within 100 ps above threshold fluence. These results are rationalized within the framework of the Landau theory of phase transition as an elastically-driven and cooperative process. We foresee broad applications of the streaming powder technique to study non-reversible and ultrafast dynamics.

2.
J Synchrotron Radiat ; 30(Pt 5): 1003-1012, 2023 Sep 01.
Article in English | MEDLINE | ID: mdl-37462688

ABSTRACT

Following Phase 2 of the upgrade of the ESRF in which the storage ring was replaced by a new low-emittance ring along with many other facility upgrades, the status of ID22, the high-resolution powder-diffraction beamline, is described. The beamline has an in-vacuum undulator as source providing X-rays in the range 6-75 keV. ID22's principle characteristics include very high angular resolution as a result of the highly collimated and monochromatic beam, coupled with a 13-channel Si 111 multi-analyser stage between the sample and a Dectris Eiger2 X 2M-W CdTe pixel detector. The detector's axial resolution allows recorded 2θ values to be automatically corrected for the effects of axial divergence, resulting in narrower and more-symmetric peaks compared with the previous fixed-axial-slit arrangement. The axial acceptance can also be increased with increasing diffraction angle, thus simultaneously improving the statistical quality of high-angle data. A complementary Perkin Elmer XRD1611 medical-imaging detector is available for faster, lower-resolution data, often used at photon energies of 60-70 keV for pair-distribution function analysis, although this is also possible in high-resolution mode by scanning up to 120°â€…2θ at 35 keV. There are various sample environments, allowing sample temperatures from 4 K to 1600°C, a capillary cell for non-corrosive gas atmospheres in the range 0-100 bar, and a sample-changing robot that can accommodate 75 capillary samples compatible with the temperature range 80 K to 950°C.

3.
Nat Commun ; 13(1): 3003, 2022 May 30.
Article in English | MEDLINE | ID: mdl-35637233

ABSTRACT

Nanostructures with specific crystallographic planes display distinctive physico-chemical properties because of their unique atomic arrangements, resulting in widespread applications in catalysis, energy conversion or sensing. Understanding strain dynamics and their relationship with crystallographic facets have been largely unexplored. Here, we reveal in situ, in three-dimensions and at the nanoscale, the volume, surface and interface strain evolution of single supported platinum nanocrystals during reaction using coherent x-ray diffractive imaging. Interestingly, identical {hkl} facets show equivalent catalytic response during non-stoichiometric cycles. Periodic strain variations are rationalised in terms of O2 adsorption or desorption during O2 exposure or CO oxidation under reducing conditions, respectively. During stoichiometric CO oxidation, the strain evolution is, however, no longer facet dependent. Large strain variations are observed in localised areas, in particular in the vicinity of the substrate/particle interface, suggesting a significant influence of the substrate on the reactivity. These findings will improve the understanding of dynamic properties in catalysis and related fields.

4.
Rev Sci Instrum ; 91(6): 065103, 2020 Jun 01.
Article in English | MEDLINE | ID: mdl-32611058

ABSTRACT

The electric-field-induced and temperature induced dynamics of domains, defects, and phases play an important role in determining the macroscopic functional response of ferroelectric and piezoelectric materials. However, distinguishing and quantifying these phenomena remains a persistent challenge that inhibits our understanding of the fundamental structure-property relationships. In situ dark field x-ray microscopy is a new experimental technique for the real space mapping of lattice strain and orientation in bulk materials. In this paper, we describe an apparatus and methodology for conducting in situ studies of thermally and electrically induced structural dynamics and demonstrate their use on ferroelectric BaTiO3 single crystals. The stable temperature and electric field apparatus enables simultaneous control of electric fields up to ≈2 kV/mm at temperatures up to 200 °C with a stability of ΔT = ±0.01 K and a ramp rate of up to 0.5 K/min. This capability facilitates studies of critical phenomena, such as phase transitions, which we observe via the microstructural change occurring during the electric-field-induced cubic to tetragonal phase transition in BaTiO3 at its Curie temperature. With such systematic control, we show how the growth of the polar phase front and its associated ferroelastic domains fall along unexpected directions and, after several cycles of electric field application, result in a non-reversible lattice strain at the electrode-crystal interface. These capabilities pave the way for new insights into the temperature and electric field dependent electromechanical transitions and the critical influence of subtle defects and interfaces.

5.
Inorg Chem ; 55(21): 11337-11341, 2016 Nov 07.
Article in English | MEDLINE | ID: mdl-27740772

ABSTRACT

Reacting Cs2O1.3, TiTe, TiO2, and Te under inert conditions gives powders of Cs1-xTi2Te2O (x ≈ 0.2). Small single crystals of the same phase were obtained from a CsCl salt melt in closed ampoules. This cesium dititanium ditelluride oxide (P4/mmm, a = 4.0934(3) Å, c = 8.9504(9) Å) is isostructural to CeCr2Si2C and contains layers of face-sharing trans-TiTe4O2 octahedra that are separated by Cs. As Ti occupies only one crystallographic site, its average oxidation state is +2.6, for the Cs deficit x = 0.2. The formally intermediate Ti valence state agrees well with the metallic conductivity and temperature-independent paramagnetic behavior. No superconductivity is observed down to 0.1 K in Cs0.8Ti2Te2O, but the fact that this structure type can accommodate Te2- suggests that electron doping of structurally closely related pnictide oxide superconductors, for example, BaTi2Bi2O, might be possible.

6.
J Pharm Sci ; 105(7): 2129-38, 2016 07.
Article in English | MEDLINE | ID: mdl-27287516

ABSTRACT

Ice formation and recrystallization is a key phenomenon in freezing and freeze-drying of pharmaceuticals and biopharmaceuticals. In this investigation, high-resolution synchrotron X-ray diffraction is used to quantify the extent of disorder of ice crystals in binary aqueous solutions of a cryoprotectant (sorbitol) and a protein, bovine serum albumin. Ice crystals in more dilute (10 wt%) solutions have lower level of microstrain and larger crystal domain size than these in more concentrated (40 wt%) solutions. Warming the sorbitol-water mixtures from 100 to 228 K resulted in partial ice melting, with simultaneous reduction in the microstrain and increase in crystallite size, that is, recrystallization. In contrast to sorbitol solutions, ice crystals in the BSA solutions preserved both the microstrain and smaller crystallite size on partial melting, demonstrating that BSA inhibits ice recrystallization. The results are consistent with BSA partitioning into quasi-liquid layer on ice crystals but not with a direct protein-ice interaction and protein sorption on ice surface. The study shows for the first time that a common (i.e., not-antifreeze) protein can have a major impact on ice recrystallization and also presents synchrotron X-ray diffraction as a unique tool for quantification of crystallinity and disorder in frozen aqueous systems.


Subject(s)
Cryoprotective Agents/chemistry , Proteins/chemistry , Calorimetry, Differential Scanning , Crystallization , Freeze Drying , Freezing , Particle Size , Pharmaceutical Solutions , Serum Albumin, Bovine/chemistry , Sorbitol/chemistry , Synchrotrons , X-Ray Diffraction
7.
Chemistry ; 22(13): 4626-31, 2016 Mar 18.
Article in English | MEDLINE | ID: mdl-26879367

ABSTRACT

The novel host-guest compound [Cs6Cl][Fe24Se26] (I4/mmm; a=11.0991(9), c=22.143(2) Å) was obtained by reacting Cs2Se,CsCl, Fe, and Se in closed ampoules. This is the first member of a family of compounds with unique Fe-Se topology, which consists of edge-sharing, extended fused cubane [Fe8Se6Se8/3] blocks that host a guest complex ion, [Cs6Cl](5+). Thus Fe is tetrahedrally coordinated and divalent with strong exchange couplings, which results in an ordered antiferromagnetic state below TN =221 K. At low temperatures, a distribution of hyperfine fields in the Mössbauer spectra suggests a structural distortion or a complex spin structure. With its strong Fe-Se covalency, the compound is close to electronic itinerancy and is, therefore, prone to exhibit tunable properties.


Subject(s)
Cesium/chemistry , Chlorides/chemistry , Ferrous Compounds/chemistry , Organometallic Compounds/chemistry , Crystallography, X-Ray , Models, Molecular , Spectrum Analysis
8.
Chemistry ; 21(21): 7938-43, 2015 May 18.
Article in English | MEDLINE | ID: mdl-25876532

ABSTRACT

Through a solid-state reaction, a practically phase pure powder of Ba3 V2 S4 O3 was obtained. The crystal structure was confirmed by X-ray single-crystal and synchrotron X-ray powder diffraction (P63 , a=10.1620(2), c=5.93212(1) Å). X-ray absorption spectroscopy, in conjunction with multiplet calculations, clearly describes the vanadium in charge-disproportionated V(III) S6 and V(V) SO3 coordinations. The compound is shown to be a strongly correlated Mott insulator, which contradicts previous predictions. Magnetic and specific heat measurements suggest dominant antiferromagnetic spin interactions concomitant with a weak residual ferromagnetic component, and that intrinsic geometric frustration prevents long-range order from evolving.

9.
J Mol Biol ; 421(1): 100-11, 2012 Aug 03.
Article in English | MEDLINE | ID: mdl-22575890

ABSTRACT

Antibodies and prorenin mutants have long been used to structurally characterize prorenin, the inactive proenzyme form of renin. They were designed on the basis of homology models built using other aspartyl protease proenzyme structures since no structure was available for prorenin. Here, we present the first X-ray structure of a prorenin. The current structure of prorenin reveals that, in this zymogene, the active site of renin is blocked by the N-terminal residues of the mature version of the renin molecule, which are, in turn, covered by an Ω-shaped prosegment. This prevents access of substrates to the active site. The departure of the prosegment on activation induces an important global conformational change in the mature renin molecule with respect to prorenin: similar to other related enzymes such as pepsin or gastricsin, the segment that constitutes the N-terminal ß-strand in renin is displaced from the renin active site by about 180° straight into the position that corresponds to the N-terminal ß-strand of the prorenin prosegment. This way, the renin active site will become completely exposed and capable of carrying out its catalytic functions. A unique inactivation mechanism is also revealed, which does not make use of a lysine against the catalytic aspartates, probably in order to facilitate pH-independent activation [e.g., by the (pro)renin receptor].


Subject(s)
Renin/chemistry , Renin/metabolism , Amino Acid Sequence , Antibodies/metabolism , Catalytic Domain , Crystallography, X-Ray , Enzyme Activation , Humans , Lysine , Models, Molecular , Molecular Sequence Data , Protein Conformation , Receptors, Cell Surface/metabolism , Renin/genetics , Prorenin Receptor
10.
Acta Crystallogr D Biol Crystallogr ; 66(Pt 5): 539-48, 2010 May.
Article in English | MEDLINE | ID: mdl-20445229

ABSTRACT

Different polymorphs of rasburicase, a recombinant urate oxidase enzyme (Uox) from Aspergillus flavus, were obtained as a series of polycrystalline precipitates. Different crystallization protocols were followed in which the salt type, pH and polyethylene glycol 8000 (PEG 8000) concentration were varied. The related crystalline phases were characterized by means of high-resolution synchrotron X-ray powder diffraction. In all cases, Uox complexed with the inhibitor 8-azaxanthine (AZA) was not altered from its robust orthorhombic I222 phase by variation of any of the factors listed above. However, in the absence of AZA during crystallization ligand-free Uox was significantly affected by the type of salt, resulting in different crystal forms for the four salts tested: sodium chloride, potassium chloride, ammonium chloride and ammonium sulfate. Remarkable alterations of some of these phases were observed upon gradual increase of the exposure time of the sample to the synchrotron beam in addition to variation of the PEG 8000 concentration. When Uox was crystallized in Tris buffer or pure water in the absence of salt, a distinct polymorph of orthorhombic symmetry (P2(1)2(1)2) was obtained that was associated with significantly altered lattice dimensions in comparison to a previously reported isosymmetrical structure. The latter form of Uox exhibits enhanced stability to variation of pH and PEG 8000 concentration accompanied by minor modifications of the unit-cell dimensions in the ranges under study. Accurate lattice parameters were extracted for all crystalline phases. This study reveals the rich phase diagram of Uox, a protein of high pharmaceutical importance, which is associated with an enhanced degree of polymorphism. The outcome of our analysis verifies previously reported results as well as demonstrating polymorphs that have altered unit-cell dimensions with respect to known structural models.


Subject(s)
Aspergillus flavus/enzymology , Urate Oxidase/chemistry , Crystallization , Crystallography, X-Ray , Phase Transition
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