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The polymorphism of human insulin upon pH variation was characterized via X-ray powder diffraction, employing a crystallization protocol previously established for co-crystallization with phenolic derivatives. Two distinct rhombohedral (R3) polymorphs and one cubic (I213) polymorph were identified with increasing pH, corresponding to the T6, T3R3 f and T2 conformations of insulin, respectively. The structure of the cubic T2 polymorph was determined via multi-profile stereochemically restrained Rietveld refinement at 2.7 Å resolution. This constitutes the first cubic insulin structure to be determined from crystals grown in the presence of zinc ions, although no zinc binding was observed. The differences of the polycrystalline variant from other cubic insulin structures, as well as the nature of the pH-driven phase transitions, are discussed in detail.

Regular injections of insulin provide life-saving benefits to millions of diabetics. Apart from native insulin and insulin analogue formulations, microcrystalline insulin suspensions are also commercially available. The onset of action of the currently available basal insulins relies on the slow dissociation of insulin hexamers in the subcutaneous space due to the strong binding of small organic ligands. With the aim of identifying insulin–ligand complexes with enhanced pharmacokinetic and pharmacodynamic profiles, the binding affinity of two resorcinol-based molecules (4-chlororesorcinol and 4-bromoresorcinol) and the structural characteristics of insulin upon co-crystallization with them were investigated in the present study. `In solution' measurements were performed via saturation transfer difference (STD) NMR. Co-crystallization upon pH variation resulted in the production of polycrystalline precipitates, whose structural characteristics (i.e. unit-cell symmetry and dimension) were assessed. In both cases, different polymorphs (four and three, respectively) of monoclinic symmetry (P21 and C2 space groups) were identified via X-ray powder diffraction. The results demonstrate the efficiency of a new approach that combines spectroscopy and diffraction techniques and provides an innovative alternative for high-throughput examination of insulin and other therapeutic proteins.

The structures of polycrystalline Ca3RE2(BO3)4(RE = La, Pr, Nd, Sm, Gd, Tb, Dy, Ho, Er, Y; space groupPnma) orthoborates were determined using powder X-ray diffraction. Trends in the unit-cell dimensions and yet unreported trends in other structural properties (interatomic distances and the fractional occupation of three Ca/RE sites) for these compounds are demonstrated as a function of RE ionic radius. The unit-cell volume andaunit-cell parameter present a linear dependence, while thebandcunit-cell parameters change in a nonlinear manner. For the whole series, the RE atoms are present at all three cationic sites (labelled asM1,M2 andM3), but the fractional occupancies depend on the RE ionic radius. The small rare-earth atoms tend to enter mainly theM3 site; for the larger rare earths, the occupancy of this site decreases sharply. The occupancy of theM1 site by RE atoms is around 0.5 and tends to increase with increasing RE ionic radius. TheM2 site is the least preferentially occupied by RE ions, but the occupancy discernibly increases with rising radius as well. These findings are assembled with properties of isostructural strontium and barium borates, allowing prediction of occupancy schemes for not yet investigated compounds from theA3RE2(BO3)4(A= Ca, Ba, Sr).

The rational design of metal-organic frameworks (MOFs) is highly important for the development of new proton conductors. Porphyrinylphosphonate-based MOFs, providing the directed tuning of physical and chemical properties of materials through the modification of a macrocycle, are potentially high-conducting systems. In this work the synthesis and characterization of novel anionic Zn-containing MOF based on palladium(ii) meso-tetrakis(3-(phosphonatophenyl))porphyrinate, IPCE-2Pd, are reported. Moreover, the proton-conductive properties and structures of two anionic Zn-containing MOFs based on previously described nickel(ii) and novel palladium(ii) porphyrinylphosphonates, IPCE-2M (M = Ni(ii) or Pd(ii)), are compared in details. The high proton conductivity of 1.0 × 10-2 S cm-1 at 75 °C and 95% relative humidity (RH) is revealed for IPCE-2Ni, while IPCE-2Pd exhibits higher hydrolytic and thermal stability of the material (up to 420 °C) simultaneously maintaining a comparable value of conductivity (8.11 × 10-3 S cm-1 at 95 °C and 95% RH). The nature of the porphyrin metal center is responsible for the features of crystal structure of materials, obtained under identical reaction conditions. The structures of IPCE-2Pd and its dehydrated derivative IPCE-2Pd-HT are determined from the synchrotron powder diffraction data. The presence of phosphonic groups in compared materials IPCE-2M affords a high concentration of proton carriers that together with the sorption of water molecules leads to a high proton conductivity.

Powder X-ray diffraction (PXRD) has been employed extensively for the structural characterization of materials, quantitative analysis of multicomponent mixtures, phase identification, texture, and ...

This study focuses on the polymorphism of human insulin (HI) upon the binding of the phenolic derivativesp-coumaric acid ortrans-resveratrol over a wide pH range. The determination of the structural behaviour of HI via X-ray powder diffraction (XRPD) and single-crystal X-ray diffraction (SCXRD) is reported. Four distinct polymorphs were identified, two of which have not been reported previously. The intermediate phase transitions are discussed. One of the novel monoclinic polymorphs displays the highest molecular packing among insulin polymorphs of the same space group to date; its structure was elucidated by SCXRD. XRPD data collection was performed using a variety of instrumental setups and a systematic comparison of the acquired data is presented. A laboratory diffractometer was used for screening prior to high-resolution XRPD data collection on the ID22 beamline at the European Synchrotron Radiation Facility. Additional measurements for the most representative samples were performed on the X04SA beamline at the Swiss Light Source (SLS) using the MYTHEN II detector, which allowed the detection of minor previously untraceable impurities and dramatically improved thed-spacing resolution even for poorly diffracting samples.

The structure of calcium europium orthoborate, Ca3Eu2(BO3)4, was determined using high-resolution powder X-ray diffraction data collected at the ID22 beamline (ESRF) under ambient conditions, as well as at high temperature. Rietveld refinement allowed determination of the lattice constants and structural details, including the Ca/Eu ratios at the three cationic sites and their evolution with temperature. Clear thermal expansion anisotropy was found, and slope changes of lattice-constant dependencies on temperature were observed at 923 K. Above this temperature the changes in occupation of the Ca/Eu sites occur, exhibiting a tendency towards a more uniform Eu distribution over the three Ca/Eu sites. Possible structural origins of the observed thermal expansion anisotropy are discussed.

In this study, the first crystal structure of a novel crystal form of human insulin bound tometa-cresol in an acidic environment is reported. The combination of single-crystal and powder X-ray diffraction crystallography led to the detection of a previously unknown monoclinic phase (P21). The structure was identified from the powder patterns and was solved using single-crystal diffraction data at 2.2 Å resolution. The unit-cell parameters at pH 6.1 area= 47.66,b = 70.36,c = 84.75 Å, β = 105.21°. The structure consists of two insulin hexamers per asymmetric unit. The potential use of this insulin form in microcrystalline drugs is discussed.

Electrical switching of ferroelectric domains and subsequent domain wall motion promotes strong piezoelectric activity; however, light scatters at refractive index discontinuities such as those found at domain wall boundaries. Thus, simultaneously achieving large piezoelectric effect and high optical transmissivity is generally deemed infeasible. Here, it is demonstrated that the ferroelectric domains in perovskite Pb(In1/2 Nb1/2 )O3 Pb(Mg1/3 Nb2/3 )O3 -PbTiO3 domain-engineered crystals can be manipulated by electrical field and mechanical stress to reversibly and repeatably, with small hysteresis, transform the opaque poly-domain structure into a highly transparent mono-domain state. This control of optical properties can be achieved at very low electric fields (less than 1.5 kV cm-1 ) and is accompanied by a large (>10000 pm V-1 ) piezoelectric coefficient that is superior to that of linear state-of-the-art materials by a factor of three or more. The coexistence of tunable optical transmissivity and high piezoelectricity paves the way for a new class of photonic devices. This article is protected by copyright. All rights reserved.

The determination of crystal structures from powder X-ray diffraction (PXRD) data by using direct-space methods is significantly limited by the degrees of conformational freedom (DOF). This limit c...

While proteins can often be stabilized by maintaining them in the frozen state, water-to-ice transformation can also lead to degradation of protein molecules. A new method to study protein/ice interaction is presented herein, which is based on measuring the characteristic features of X-ray diffraction (XRD) patterns of hexagonal ice (Ih). Aqueous solutions of four different proteins and several small molecular weight solutes are studied using high-resolution synchrotron X-ray diffraction at the ID22 beamline at the European Synchrotron Radiation Facility. The beamline is optimized to eliminate the instrumental broadening of diffraction lines and reduce the preferred orientation effects, thereby enabling quantitative analysis of the XRD data. The analysis demonstrates that two pharmaceutical proteins, recombinant human albumin (rHA) and monoclonal antibody (mAb), have a pronounced effect on the properties of ice crystals. In particular, the size of the crystalline domains is significantly smaller, and the microstrain is larger, in the solutions of the pharmaceutical proteins, when compared with a model protein (lysozyme), an antifreeze protein, and sucrose and histidine. Neither of the proteins studied exhibit preferred interaction with specific crystalline faces of Ih. The results are consistent with indirect interaction of the pharmaceutical proteins with ice, in which protein molecules are accumulated in the quasi-liquid layer next to growing ice crystallization front. Direct interaction would indicate a sorption of protein molecules on ice crystals, whereas “indirect interaction” terminology is used to describe any interference of proteins with ice crystals without sorption involved. Lysozyme molecules, on the other hand, do not exhibit any evidence of interaction (either direct or indirect) with ice crystals. This is the first report, to the best of our knowledge, of major difference in protein/ice interaction between different types of non-antifreeze proteins. In addition, we report an unexpected finding of a second population of ice crystals, with a much smaller (a few nm) size of crystalline domains. The second (minor) population is tentatively identified as a high-pressure form of ice, possibly IceIII or IceIX. This observation highlights a potential role of mechanical stresses and local pressure in freeze-induced destabilization of proteins.

The structures of polycrystalline Ca

International audience; A crystallographic approach incorporating multinuclear high field solid state NMR (SSNMR), X-ray structure determinations, TEM observation, and density functional theory (DFT) was used to characterize two polymorphs of rubid-ium cryolite, Rb3AlF6. The room temperature phase was found to be ordered and crystallizes in the Fddd (n°70) space group with a = 37.26491(1) Å, b = 12.45405(4) Å, c = 17.68341(6) Å. Comparison of NMR measurements and computational results revealed the dynamic rotations of the AlF6 octahedra. Using in-situ variable temperature MAS NMR measurements, the chemical exchange between rubidium sites was observed. The β-phase, i.e. high temperature polymorph, adopts the ideal cubic double-perovskite structure, space group 3 ̅ , with a = 8.9930(2) Å at 600 °C. Additionally, a series of polymorphs of K3AlF6 has been further characterized by high field high temperature SSNMR and DFT computation.

An analysis of known synthetic methods for dibenzoylmethanide (dbm−) complexes of lanthanides of different nuclearity, viz. [Ln(dbm)3(H2O)], [Ln4(dbm)10(OH)2], [Ln5(dbm)10(OH)5] and [KLn(dbm)4]n (Ln = Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Yb) has been carried out. These methods have been optimized, the range of lanthanides for the compounds extended, and novel complex species, viz. [KLn(Me2CO)(dbm)4]2 (Ln = Eu, Dy, Yb) and [Nd3(dbm)8(OH)(H2O)], have been produced. The nature of the lanthanides in some cases affects the composition of the products formed. The compound [KEu(Me2CO)(dbm)4]2 in solution can transform to [KEu(dbm)3(OBz)]n, containing benzoate (OBz−). For the seven new complexes, the crystal structures have been determined by X-ray diffraction. Photoluminescent properties of the europium complexes have been studied. Their composition and structure influence the emission band shape and quantum yields. Two solid solutions of heterolanthanide complexes [ErxYb5–x(dbm)10(OH)5] (x = 1.2, 2.0) have been prepared, as shown by high-resolution powder XRD analysis.

Formation of stable porous frameworks based on cyclic peptoids can be triggered by strategic choice of appropriate side chains. In this contribution we demonstrate that substitution of distal propargyl side chains with methoxyethyl groups in a fully propargylated cyclic octamer peptoid (cyclo-(Npa)8 1) greatly improves the solid state stability inducing permanent one-dimensional porosity of the compound (cyclo-[(NPa)3(Nme)]2 2, Npa = N-(propargyl)glycine, Nme = N-(methoxyethyl)glycine). In both compounds the macrocycles align along the shortest cell axis to form tubes that are filled with guest molecules. In situ hydration and dehydration single crystal X-ray diffraction studies on compound 2 demonstrated the improved stability of the host framework. Hirshfeld surface analysis and lattice energy calculations, also supported by energy frameworks analysis, clarified the determinant packing motifs in the studied compounds explaining the improved stability in terms of architectural robustness. Methoxyethyl si...

Uncertainties in the structure determination of peptide analogs of boronic acid, exacerbated by the many coordination modes of boron, represent an obstacle in understanding their role in living organisms and thus also in developing the next generation of anticancer drugs. For that reason, we present here a general experimental-computational strategy allowing structure determination of complex boronic acid derivatives with extensive conformational variability. We demonstrate successful solution of the crystal structures of two nonsolvated polymorphs of ixazomib citrate directly from synchrotron powder diffraction data, which is challenging because the two molecules in the asymmetric unit cell that exhibit 32 degrees of conformational freedom push the limits of current solution procedures. We used a novel two-step Rietveld refinement based on DFT-D restraints to improve information quality derived from powder diffraction data to be comparable with that of single-crystal solutions. NMR crystallography was ap...

Flavivirus infections often provoke life-threatening diseases of epidemic magnitudes, thus extensive research is currently directed towards the development of efficient vaccines and approved antiviral compounds. We present here the expression, purification, crystallization and preliminary X-ray diffraction analysis of one of the components of the flavivirus replication complex, the non-structural protein 5 (NS5) mRNA methyltransferase (MTase) domain, from an emerging pathogenic flavivirus, dengue virus 3 (DEN3). Polycrystalline precipitates of DEN3 NS5 MTase, suitable for X-ray powder diffraction (XRPD) measurements, were produced in the presence of PEG 8000 (25–32.5% (w/v)), 0.1 M Tris-Amino, in a pH range from 7.0 to 8.0. A polymorph of orthorhombic symmetry (space group: P21212, a=61.9 Å, b=189.6 Å, c=52.4 Å) was identified via XRPD. These results are the first step towards the complete structural determination of this molecule via XRPD and a parallel demonstration of the applicability of the method.

Materials of the Ca 9 RE(VO 4 ) 7 (CRVO) formula (RE = rare earth) and whitlockite-related structures are considered for applications in optoelectronics, e.g. , in white-light emitting diodes and lasers. In the CRVO structure, the RE atoms are known to share the site occupation with Ca atoms at two or three among four Ca sites, with partial occupancy values depending on the choice of the RE atom. In this work, the structure and quality of a Czochralski-grown crystal of this family, Ca 9 Gd(VO 4 ) 7 (CGVO), are studied using X-ray diffraction methods. The room-temperature structure is refined using the powder diffraction data collected at a high-resolution synchrotron beamline ID22 (ESRF, Grenoble); for comparison purposes, a laboratory diffraction pattern was collected and analyzed, as well. The site occupancies are discussed on the basis of comparison with literature data of isostructural synthetic crystals of the CRVO series. The results confirm the previously reported site-occupation scheme and indicate a tendency of the CGVO compound to adopt a Gd-deficient composition. Moreover, the thermal expansion coefficient is determined for CGVO as a function of temperature in the 302–1023 K range using laboratory diffraction data. Additionally, for CGVO and six other single crystals of the same family, thermal expansion is studied in the 298–473 K range, using the dilatometric data. The magnitude and anisotropy of thermal expansion, being of importance for laser applications, are discussed for these materials.

A practical synthesis of new phosphoramidite, phosphite and diamidophosphite P , N -ligands derived from ( R , R )-tartaric acid was carried out. A study of these chiral inducers showed them to provide up to 93% ee in the Pd-catalyzed asymmetric allylations of ( E )-1,3-diphenylallyl acetate, up to 84% ee in the Pd-catalyzed asymmetric alkylation of cinnamyl acetate with ethyl 2-oxocyclohexane-1-carboxylate and up to 63% ee in the Pd-catalyzed desymmetrization of N , N ′-ditosyl- meso -cyclopent-4-ene-1,3-diol biscarbamate. The effects of the structural modules, such as the nature of the phosphorus-containing ring or exocyclic substituent as well as of the nature of palladium source on the catalytic activity and enantioselectivity were investigated.

A versatile approach for the synthesis of [1,2,4]triazolodipyrimidinones with various annulations of the triazole and pyrimidine rings was developed. The isomeric triazolodipyrimidinones were obtained by the stepwise condensation of partially hydrogenated [1,2,4]triazolo[1,5-a]pyrimidin-2-amines with β-ketoesters or diethyl ethoxymethylenemalonate, alkoxy base-mediated cyclization of the enamines, and subsequent cascade rearrangement of the 10-oxo-[1,2,4]triazolo[1,5-a:4,3-a′]dipyrimidines.

The structure of calcium europium orthoborate, Ca

The localization and distribution of germanium atoms in the framework positions of Ge-BEC zeolite upon silylation have been studied using synchrotron XRD and 19F NMR. The high thermal stability of Ge-BEC material synthesized using 1-benzyl-1,4-diazabicyclo[2.2.2]octane as the structure-directing agent (SDA) has been observed, enabling the preparation of calcined Ge-BEC. Unexpectedly, the inhomogeneous enrichment of double-four membered ring (d4r) subunits in the BEC structure with germanium has been observed. The interaction of germanosilicate with (NH4)2SiF6 led to the selective substitution of germanium atoms in T2 and T3 positions with silicon, while fluoride anions preferably occupy positions inside d4r subunits.

Series of the mixed cobaltites-ferrites RCo1−xFexO3 (x = 0.1–0.9) and cobaltites-chromites RCo0.5Cr0.5O3 (R = Pr, Nd, Sm, Eu, Gd, Tb, Dy, Er) with the orthorhombic perovskite structure (space group Pbnm) have been prepared from stoichiometric amounts of rare earth oxides, Co3O4, Fe2O3 and Cr2O3 by solid-state reaction in air at 1473–1573 K. In situ high-temperature X-ray synchrotron powder diffraction revealed anomalous lattice expansion of both series, which is reflected in a sigmoidal dependence of the unit cell dimensions and in abnormal anisotropic increase of the thermal expansion coefficients (TEC). Depending on the composition, several broad maxima in the temperature range of 500−1000 K are observed, which are evidently connected with the transitions of Co3+ cations to the higher spin states. The observed anomalies in the mixed cobaltites-ferrites and cobaltites-chromites are less pronounced compared with the corresponding “pure” cobaltites.

Transition from an amorphous to a crystalline phase and stabilization of amorphous phases is a common strategy in biomineralization. Although no such phenomenon has yet been reported for biogenic calcium oxalate systems, it was recently demonstrated for synthetic calcium oxalate monohydrate (COM). Here we focused on COM raphides—needle shaped biominerals—synthesized by Duckweed. Although these raphides show some birefringence in polarized light, implying their crystallinity, they diffracted poorly when examined by x-ray diffraction in our experiments. By means of transmission electron microscopy coupled with electron diffraction experiments we demonstrated that raphides from Duckweed are completely amorphous in their tip region and transform into a crystalline phase under the electron beam after a few seconds of exposure. To the best of our knowledge, this is the first report on biogenic amorphous calcium oxalate produced by a living organism.

Natural or artificially manufactured peptides attract scientific interest worldwide owing to their wide array of pharmaceutical and biological activities. X-ray structural studies are used to provide a precise extraction of information, which can be used to enable a better understanding of the function and physicochemical characteristics of peptides. Although it is vulnerable to disassociation, one of the most vital human peptide hormones, somatostatin, plays a regulatory role in the endocrine system as well as in the release of numerous secondary hormones. This study reports the successful crystallization and complete structural model of octreotide, a stable octapeptide analogue of somatostatin. Common obstacles in crystallographic studies arising from the intrinsic difficulties of obtaining a suitable single-crystal specimen were efficiently overcome as polycrystalline material was employed for synchrotron and laboratory X-ray powder diffraction (XPD) measurements. Data collection and preliminary analysis led to the identification of unit-cell symmetry [orthorhombic,P212121,a= 18.5453 (15),b= 30.1766 (25),c= 39.798 (4) Å], a process which was later followed by complete structure characterization and refinement, underlying the efficacy of the suggested (XPD) approach.

© 2018 Académie des sciences Cultural heritage materials are often complex and heterogeneous, with a multi-scale architecture. Phases from a variety of crystalline forms co-exist in a wide grain size distribution, with each of these phases keeping in their structural arrangement a memory of the transformations that occurred to the material. Over the last two decades, X-ray diffraction has been applied successfully to the study of cultural heritage materials, with the use of synchrotron facilities offering new possibilities to describe the structural features of such complex materials. The long-range and/or short-range organization of the different crystallographic phases as well as their global position/dispersion in the material are closely related to the properties of the material (optical, mechanical…), its manufacturing process, functionality, or long-term conservation. In this paper, possible diffraction setups and data collection strategies are discussed in order to retrieve adequate data from crystalline and amorphous phases and to take into account single-crystal contributions.

Aim: Synthesis of novel bronchodilatory active indole–pyridine conjugates. Results/methodology: Indole–pyridine conjugates (6a–n, 8a–i and 10a–c) were synthesized in a facile pathway through reaction of 2-[(1-alkyl-1H-indol-3-yl)methylene]malononitriles 4a,b with the corresponding ketone-containing compounds (5a–f, 7a–c and 9a,b) in the presence of sodium alkoxide. Single (6l, 8 g) and powder (6k, 8d) x-ray studies supported the structures. Results: Histamine precontracted isolated tracheal rings of guinea pig exhibited the potent bronchodilation properties of 6c (about double-fold potency relative to the standard reference, theophylline). Some of the synthesized conjugates (8d, 6c, 6f and 6e) revealed promising reduction of IL-8 production during lipopolysaccharide-induced airway inflammatory bioassay. Computational studies (3D pharmacophore, 2D-QSAR ‘quantitative structure–activity relationship’) showed high approximations to the bronchodilation properties and explained the parameters controlling biological observations.

The synthesis of 3D covalent organic frameworks (COFs) adopting novel topologies is challenging, and so far 3D COFs have only been reported for nets based on building blocks with tetrahedral geometry. We demonstrate the targeted synthesis of an anionic 3D COF crystallizing in a three-coordinated srs net by exploiting a recently developed linkage for the formation of anionic silicate COFs based on hypercoordinate silicon nodes. The framework, named SiCOF-5, was synthesized by reticulating dianionic hexacoordinate [SiO6]2– nodes with triangular triphenylene building blocks and adopts a two-fold interpenetrated srs-c net with an overall composition of Na2[Si(C18H6O6)] (where C18H6O6 is triphenylene-2,3,6,7,10,11-hexakis(olate)). A key requirement for the crystallization of SiCOF-5 was the careful control over the nucleation and growth rate by gradual generation of the silicon source during the course of the reaction.

Two 3-(arylmethylidene)pyrrolidine-2,5-diones, 12a and 12b, were synthesized and characterized by powder X-ray diffraction utilizing a high-resolution synchrotron X-ray powder technique. The basic difference between the theoretical (AM1, PM3 and DFT computational studies) and experimental (X-ray diffraction) structures is the relative orientation of aryl groups attached to the pyrrolidinyl nitrogen and exocyclic olefinic linkage. The lattice form controlling the X-ray structure is responsible for these observations. Pyrrolidines 12a, b reveal vasodilation bio-properties with potency higher than that of doxazosin (clinically applicable α1-adrenergic receptor blocker).

Ag0.8In2.4Te4 (= AgIn3Te5) and Ag0.5In2.5Te4 (= AgIn5Te8) form solid solutions with CdIn2Te4, which are interesting as materials for photovoltaics or with respect to their thermoelectric properties. The corresponding crystal structures are related to the chalcopyrite type. Rietveld refinements of high-resolution synchrotron powder diffraction data measured at K-absorption edges of Cd, Ag, In, and Te and electron diffraction reveal the symmetry as well as the element and vacancy distribution in Ag0.8In2.4Te4 (= AgIn3Te5)/Ag0.5In2.5Te4 (= AgIn5Te8) mixed crystals such as Ag0.25Cd0.5In2.25Te4 and Ag0.2Cd0.75In2.1Te4. All compounds of the solid solution series (CdIn2Te4)x(Ag0.5In2.5Te4)1-x exhibit the HgCu2I4 structure type (space group I4̅2m) with completely ordered vacancies but disordered cations. The uniform cation distribution and thus the local charge balance are comparable to that of CdIn2Te4. In contrast, Ag0.8In2.4Te4 (= AgIn3Te5) crystallizes in the space group P4̅2c with disordered cations and partially ordered vacancies. This is corroborated by bond-valence sum calculations and the fact that there is a Vegard-like behavior for compounds with 0.5x in the pseudobinary system (CdIn2Te4)x(Ag0.8In2.4Te4)1-x. Owing to the different structures, there is no complete solid solution series between CdIn2Te4 and AgIn3Te5. All compounds in this work are n-type semiconductors with a low electrical conductivity (∼1 S/m) and rather high absolute Seebeck coefficients (up to -750 μV/mK; 225 °C). Electrical band gaps (Eg) determined from the Seebeck coefficients as well as (more reliably) from the electrical conductivity range between 0.19 and 1.13 eV.

New magnesium-based bulk metallic glasses Mg60Cu30Y10 have been prepared by pressure casting. Glassy alloys were successfully annealed to become nanocomposite containing 200 nm crystallites in an amorphous matrix. The microstructure of bulk glassy alloy and nanocomposite obtained during heat treatment was examined by X-ray diffraction and scanning and high-resolution electron microscopy. Metallic glass has been also studied to explain the structural characteristics by the reverse Monte Carlo (RMC) modeling based on the diffraction data. The HRTEM images allow to indicate some medium-range order (MRO) regions about 2–3 nm in size and formation of local atomic clusters. The RMC modeling results confirmed some kinds of short range order (SRO) structures. It was found that the structure of bulk metallic glass formed by the pressure casting is homogeneous. The composite material contained very small particles in the amorphous matrix. Homogeneous glassy alloy had better corrosion resistance than a composite containing nanocrystalline particles in a glassy matrix.

The crystal structure of α-Fe2O3and α-Cr2O3is usually described with the corundum-type trigonal crystal structure based on the space group R\bar 3c. There are, however, some observations of the magnetic ordering of both α-Fe2O3and α-Cr2O3that are incompatible with the trigonal symmetry. We show experimental evidence based on X-ray powder diffraction and supported by transmission electron microscopy that the symmetry of the crystal structure of both α-Fe2O3and α-Cr2O3is monoclinic and it is described with the space groupC2/c(derived from R\bar 3c by removing the threefold rotation axis). The magnetic orderings of α-Fe2O3and α-Cr2O3are compatible with the magnetic space groupsC2/candC2/c′, respectively. These findings are in agreement with the idea from Curie [(1894),J. Phys.3, 393–415] that the dissymmetry of the magnetic ordering should be associated with a dissymmetry of the crystal structure.

By means of powder neutron diffraction we investigate changes in the magnetic structure of the coplanar noncollinear antiferromagnet ${\mathrm{Mn}}_{3}\mathrm{Ge}$ caused by an application of hydrostatic pressure up to 5 GPa. At ambient conditions the kagom\'e layers of Mn atoms in ${\mathrm{Mn}}_{3}\mathrm{Ge}$ order in a triangular ${120}^{\ensuremath{\circ}}$ spin structure. Under high pressure the spins acquire a uniform out-of-plane canting, gradually transforming the magnetic texture to a noncoplanar configuration. With increasing pressure the canted structure fully transforms into the collinear ferromagnetic one. We observed that magnetic order is accompanied by a noticeable magnetoelastic effect, namely, spontaneous magnetostriction. The latter induces an in-plane magnetostrain of the hexagonal unit cell at ambient pressure and flips to an out-of-plane strain at high pressures in accordance with the change of the magnetic structure.

Calcium oxalate crystals are the most common biominerals found in plants. They also make their presence known as painful kidney stones in humans and animals. Their function in plants is extraordinarily versatile and encompasses calcium storage and defense mechanisms against herbivores and detoxification processes. Since plants containing calcium oxalate crystals are often exposed to metallic environments, we studied the interaction of such environmental metals with calcium oxalate in vitro. We showed that selected metals are indeed incorporated into synthetic calcium oxalate, and in a manner that depends on their ionic radius when precipitated in solution. One such mechanism of incorporation is based on the replacement of calcium ions by other metal cations within the host unit cell. The unit cell of calcium oxalate expands when incorporating elements with larger atomic radii and shrinks when doped with elements possessing ionic radii smaller than that of calcium. In this systematic study, metal-doped calcium oxalate crystals were characterized by means of high-resolution synchrotron X-ray powder diffraction, energy-dispersive X-ray spectroscopy, inductively coupled plasma atomic emission spectroscopy, and transmission electron microscopy. Better understanding of metal incorporation into mineral hosts might lead to ways of developing new and more efficient sorbent materials for detoxification processes.

A novel important class of nanoporous crystalline solids, metal–organic frameworks (MOFs), composed of organic ligands (linkers) and metal ions, is now considered as a platform for the development of various functional hybrid materials. In order to design new MOF-based asymmetric catalysts, two terephthalic acid derivatives, namely 2-{[1-(1-tert-butoxycarbonyl)-L-prolyl]amino}terephthalic acid, C18H22N2O7, (1), and 2-(L-prolylamino)terephthalic acid, C13H14N2O5, (2), which could find potential applications as chiral linkers for the construction of enantioselective MOFs, were synthesized and their powder samples were measured at synchrotron station ID22 (ESRF). Each sample contained two unknown crystalline phases, so four new crystal structures were determined, namely, the 2.24-hydrate of (1), (1a) (space groupC2221), and the 2.08-hydrate of (1), (1b) (P2221), which are crystallohydrates, and two polymorphs of (2),i.e.(2a) (C2221) and (2b) (P212121), and were validated with DFT-d (dispersion-corrected density functional theory) optimizations.

A superstructure of the rocksalt-type observed in quenched CVT-grown single crystals of Ge3.25(7)Sn1.10(3)Sb1.10(3)Te6 was elucidated by X-ray diffraction using fourfold twinned crystals (space group P 3 ¯ m 1 , a=4.280(1) A, c=20.966(3) A). The structure is built up of distorted rocksalt-type building blocks typical for long-range ordered GST materials and substitution variants thereof. In contrast to those phases, an exclusive ABC-type cubic stacking sequence of the Te-atom layers is present. High-resolution electron microscopy reveals spheroidal domains with this structure (average diameter 25 nm) whose stacking direction is perpendicular to the 〈1 1 1〉 directions of the basic rocksalt-type structure. Additional slab-like domains with a lateral extension up to 1 µm occasionally result in a hierarchical structure motif. Due to the similar electron counts of the elements involved, resonant diffraction was used in order to elucidate the element distribution in rocksalt-type building blocks of the stable layered compound 39R-Ge3SnSb2Te7 ( R 3 ¯ m , a=4.24990(4) A, c=73.4677(9) A). Sb tends to occupy the atom site close to the van der Waals gaps while Ge concentrates in the center of the building blocks.

The new low valent iridiumindiumoxogallate Ir2In12Ga4O15 was prepared by heating intimate mixtures of Ir, In, In2O3, and Ga2O3 in a platinum crucible under an atmosphere of argon (1400 K, 70 h). The compound has an orange color. X-ray powder diffraction patterns can be indexed on the basis of a primitive orthorhombic unit cell with lattice parameters a = 1954.5(1) pm, b = 674.0(1) pm, and c = 745.9(1) pm. The crystal structure of Ir2In12Ga4O15 was solved from powder diffraction data and refined using the Rietveld method (Pnn2, R(prof.) = 4.4 %, R(int.) = 2.5 %). Ir2In12Ga4O15 is according to [IrIn5In2/2]9+2[GaO4]5–2[Ga2O7]8– an ortho-gallate-pyro-gallate with chains of corner sharing [IrIn7]9+ polyhedra, [GaO4]5–2 tetrahedra, and [Ga2O7]8– double tetrahedra. The Ir–In distances within the IrIn7 polyhedra are shorter than in Ir–In intermetallic phases and lie between 256–261 pm.

Compounds containing two nine-membered peroxide rings bridged by an ethane, ethene, or ethyne group were synthesized by the reactions of 1,2-bis[dichloro(alkyl)silyl]ethanes, (E)-1,2-bis[dichloro(methyl)silyl]ethene, or 1,2-bis[dichloro(methyl)silyl]ethyne with 1,1′-dihydroperoxydicycloalkyl peroxides. Each ring is formed by the replacement of two geminal chlorine atoms at the silicon atom with the hydroperoxide groups of one peroxide molecule. The cyclization is regioselective. The possible 12-membered bicyclic peroxide products are not produced. Unexpectedly, the peroxides are extremely explosive. The reactions of 1,2-bis[dichloro(alkyl)silyl]ethanes with 1,1-dihydroperoxy-tert-butylcyclohexane give only bicyclic peroxides containing two six-membered rings also through the replacement of two geminal chlorine atoms at the silicon atom by the hydroperoxide groups of one dihydroperoxide molecule.

Lineshape analysis of high resolution synchrotron radiation diffraction patterns of polycrystalline α-Fe 2 O 3 powders show distortions from trigonal (space group R-3c) symmetry. The symmetry lowering is observed for α-Fe 2 O 3 polycrystalline powders from several commercial vendors. The experimental observations can be explained by assuming a monoclinic symmetry (space group C2/c). The relative differences between the monoclinic and the hexagonal lattice constants are of the order of 10 −4 . The monoclinic symmetry of the crystal structure of α-Fe 2 O 3 (C2/c) is in agreement with magnetic space group analysis [American Mineralogist 95 (2010) 974].

High-resolution synchrotron X-ray powder diffraction (XRD) combined with the Rietveld refinement method and confocal laser scanning microscopy (CLSM) were utilized in this study to elucidate the interaction between a recombinant biomineralization protein (perlucin) fused to green fluorescent protein (GFP) and synthetic calcite. Although recombinant perlucin is insoluble, its solubility was increased via fusion to the highly soluble GFP. We demonstrate that GFP-perlucin derivatives become incorporated into the calcite structure and induce concentration-dependent anisotropic lattice distortions along the host’s c-axis. In contrast, GFP alone is hardly incorporated at all. The observed lattice distortions and peculiar microstructure of the crystals are comparable to those previously observed in biogenic calcite. Taking advantage of biotechnology to optimize individual protein properties, such as the solubility of an otherwise insoluble protein derivative, is a promising route toward the synthesis of new and ...

The reactions of 1,2-bis(dimethylchlorosilyl)ethane (1), 1,2-bis(dimethylchlorosilyl)ethene (6), and 1,2-bis(dimethylchlorosilyl)ethyne (7) with gem-bis(hydroperoxides) 2a–h and 1,1′-bis(hydroperoxy)bis(cycloalkyl)peroxides 4a–c were found to proceed in an unusual way. Thus, the reactions do not give the expected polymeric peroxides; instead, they produce cyclic silicon-containing peroxides containing 2, 4, or 6 silicon atoms in the ring: 9- (3a–h), 12- (5a–c), 18- (8, 12), 24- (9, 10), 27- (13), and 36-membered (11) compounds. The size of the rings produced in the reactions increases in the series 1,2-bis(dimethylchlorosilyl)ethane < 1,2-bis(dimethylchlorosilyl)ethene < 1,2-bis(dimethylchlorosilyl)ethyne. The resulting 9- and 12-membered cyclic peroxides are stable under ambient conditions. These compounds were isolated by chromatography and characterized by 1H, 13C, and 29Si NMR spectroscopy, X-ray diffraction, elemental analysis, and high-resolution mass spectrometry. The yields vary from 77 to 95%. St...