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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 595 records · Page 33
All sourcesNASA NTRSDOE OSTI
DOE OSTI2015

The oxygenating constituent of 3,6-diketocamphane monooxygenase from the CAM plasmid of Pseudomonas putida: the first crystal structure of a type II Baeyer–Villiger monooxygenase

The first crystal structure of a type II Baeyer–Villiger monooxygenase reveals a different ring orientation of its FMN cofactor compared with other related bacterial luciferase-family enzymes. The three-dimensional structures of the native enzyme and the FMN complex of the overexpressed form of the oxygenating component of the type II Baeyer–Villiger 3,6-diketocamphane monooxygenase have been determined to 1.9 Å resolution. The structure of this dimeric FMN-dependent enzyme, which is encoded on the large CAM plasmid of Pseudomonas putida, has been solved by a combination of multiple anomalous dispersion from a bromine crystal soak and molecular replacement using a bacterial luciferase model. The orientation of the isoalloxazine ring of the FMN cofactor in the active site of this TIM-barrel fold enzyme differs significantly from that previously observed in enzymes of the bacterial luciferase-like superfamily. The Ala77 residue is in a cis conformation and forms a β-bulge at the C-terminus of β-strand 3, which is a feature observed in many proteins of this superfamily.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2015

Crystal structure of a new amine nitrate: 4-dimethylaminopyridinium nitrate (C{sub 7}H{sub 11}N{sub 2})NO{sub 3}

The title compound (C{sub 7}H{sub 11}N{sub 2})NO{sub 3} (I) was obtained by the slow evaporation method at room temperature. Its crystal structure consists of organic cations (C{sub 7}H{sub 11}N{sub 2}){sup +} and nitrate anions (NO{sub 3}){sup –} linked by two types of hydrogen bonds. Each monoprotonated nitrogen atom, called bifurcated, is engaged in two N–H···O hydrogen bonds with two symmetric oxygen atoms. In addition, the crystal structure stability is established by C–H···O hydrogen bonds that ensure the formation of infinite layers, parallel to (001) plane. These layers are related together through π···π interactions established between aromatic amines.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2014

Phase transformation of Ca{sub 4}[Al{sub 6}O{sub 12}]SO{sub 4} and its disordered crystal structure at 1073 K

The phase transformation of Ca{sub 4}[Al{sub 6}O{sub 12}]SO{sub 4} and the crystal structure of its high-temperature phase were investigated by differential thermal analysis, temperature-dependent Raman spectroscopy and high-temperature X-ray powder diffraction (CuKα{sub 1}). We determined the starting temperature of the orthorhombic-to-cubic transformation during heating (=711 K) and that of the reverse transformation during cooling (=742 K). The thermal hysteresis was negative (=−31 K), suggesting the thermoelasticity of the transformation. The space group of the high temperature phase is I4{sup ¯}3m with the unit-cell dimensions of a=0.92426(2) nm and V=0.78955(2) nm{sup 3} (Z=2) at 1073 K. The initial structural model was derived by the direct methods and further refined by the Rietveld method. The final structural model showed the orientational disordering of SO{sub 4} tetrahedra. The maximum-entropy method-based pattern fitting method was used to confirm the validity of the split-atom model, in which conventional structure bias caused by assuming intensity partitioning was minimized. At around the transformation temperature during heating, the vibrational spectra, corresponding to the Raman-active SO{sub 4} internal stretching mode, showed the continuous and gradual change in the slope of full width at half maximum versus temperature curve. This strongly suggests that the orthorhombic-to-cubic phase transformation would be principally accompanied by the statistical disordering in orientation of the SO{sub 4} tetrahedra, without distinct dynamical reorientation. - Graphical abstract: (Left) Three-dimensional electron-density distributions of the SO{sub 4} tetrahedron with the split-atom model, and (right) a bird's eye view of electron densities on the plane parallel to (111). - Highlights: • Crystal structure of Ca{sub 4}[Al{sub 6}O{sub 12}]SO{sub 4} at 1073 K is determined by powder XRD. • The atom arrangements are represented by the split-atom model. • The MPF method is used to confirm the validity of the model. • The phase transition is accompanied by orientational disordering of SO{sub 4} tetrahedra.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2022

X-ray crystal structure of the Escherichia coli RadD DNA repair protein bound to ADP reveals a novel zinc ribbon domain

Genome maintenance is an essential process in all cells. In prokaryotes, the RadD protein is important for survival under conditions that include DNA-damaging radiation. Precisely how RadD participates in genome maintenance remains unclear. Here we present a high-resolution X-ray crystal structure of ADP-bound Escherichia coli RadD, revealing a zinc-ribbon element that was not modelled in a previous RadD crystal structure. Insights into the mode of nucleotide binding and additional structure refinement afforded by the new RadD model will help to drive investigations into the activity of RadD as a genome stability and repair factor.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2023

Role of orbital selectivity on crystal structures and electronic states in BiMnO 3 and LaMnO 3 perovskites

Correlated oxides, such as BiMnO 3 and LaMnO 3 , show a complex interplay of electronic correlations and crystal structure exhibiting multiple first-order phase transitions, some without a clear order parameter. The quantitative theoretical description of this temperature-dependent electronic-structural interplay in the vicinity of a Mott transition is still a challenge. Here we address this issue by simultaneously considering both structural and electronic degrees of freedom, within a self-consistent density functional theory with embedded dynamical mean field theory. Our results show the existence of novel electronic states characterized by the coexistence of insulating, semimetallic, and metallic orbitals. This state is in agreement with resonant x-ray scattering. Here we also show that electronic entropy plays a decisive role in both electronic and structural phase transitions. By self-consistent determination of both the electronic state and the corresponding crystal structure, we show that the temperature evolution of these phases can be quantitatively explained from first principles, thus demonstrating the predictive power of the theoretical method for both the structural and the electronic properties.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2018

Synthesis, Crystal Structure, and Magnetic Properties of the YbFeTi{sub 2}O{sub 7} Compound

We report on the synthesis conductions and results of experimental investigations of the crystal structure and magnetic properties of a new magnetic compound YbFeTi{sub 2}O{sub 7}. According to the X-ray diffractometry data, the crystal structure of the investigated compound is described by the rhombic space group Pcnb with unit cell parameters of a = 9.8115(1) Å, b = 13.5106(2) Å, and c = 7.31302(9) Å and atomic disordering in the distribution of iron ions Fe{sup 3+} over five structural sites. The magnetic measurements in the lowtemperature region revealed a kink in the temperature dependence of the magnetic moment and its dependence on the sample magnetic prehistory. The experimental results obtained suggest that with a decrease in temperature the sample passes from the paramagnetic state to the spin-glass-like magnetic state characterized by a freezing temperature of T{sub f} = 4.5 K at the preferred antiferromagnetic exchange coupling in the sample spin system. The chemical pressure variation upon replacement of rare-earth ion R by Yb in the RFeTi{sub 2}O{sub 7} system does not change the crystal lattice symmetry and magnetic state.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2014

Fano resonance control in a photonic crystal structure and its application to ultrafast switching

We experimentally demonstrate a photonic crystal structure that allows easy and robust control of the Fano spectrum. Its operation relies on controlling the amplitude of light propagating along one of the light paths in the structure from which the Fano resonance is obtained. Short-pulse dynamic measurements show that besides drastically increasing the switching contrast, the transmission dynamics itself is strongly affected by the nature of the resonance. The influence of slow-recovery tails implied by a long carrier lifetime can thus be reduced using a Fano resonance due to a hitherto unrecognized reshaping effect of the nonlinear Fano transfer function. As an example, we present a system application of a Fano structure, demonstrating its advantages by the experimental realization of 10 Gbit/s all-optical modulation with optical control power less than 1 mW.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2012

A study of the crystal structures and the phase transitions of the ordered double perovskites Sr{sub 2}ScSbO{sub 6} and Ca{sub 2}ScSbO{sub 6}

The crystal structures and phase transitions of the two ordered double perovskites Sr{sub 2}ScSbO{sub 6} and Ca{sub 2}ScSbO{sub 6} were studied using conventional X-ray and neutron powder-diffraction methods. The crystal structures of both compounds have the P2{sub 1}/n space group symmetry at room temperature, resulting from Sc/Sb ordering. The evolution with temperature of the structure of the Sr containing compound shows the presence of three phase transitions with the following sequence: P2{sub 1}/n{yields}I2/m{yields}I4/m{yields}Fm3{sup Macron }m, at about 400, 560 and 650 K, respectively. The smaller size of Ca cation, with respect to that of Sr cation, leads to a large distortion of Ca{sub 2}ScSbO{sub 6} at room temperature. This fact in turn causes that the Ca containing compound shows only the first phase transition from P2{sub 1}/n to I2/m at high temperature at about 1440 K. The analysis of the phase transitions and the refinements have done using the symmetry-adapted modes and the tools of the Bilbao Crystallographic Server. - Graphical abstract: Representation of the new structure resulting from the coupling of the unidimensional GM{sup 4+} and X{sup 3+} modes with the a{sup +}b{sup -}b{sup -} tilting scheme associated to P2{sub 1}/n and the temperature evolution of the amplitudes of the GM{sup 1+}, GM{sup 3+}, GM{sup 4+} and GM{sup 5+} modes of I2/m and I4/m space groups obtained from the NPD data of Sr{sub 2}ScSbO{sub 6}. Highlights: Black-Right-Pointing-Pointer Study of two compounds of the antimony double perovskite family. Black-Right-Pointing-Pointer Determination of the structures at room temperature. Black-Right-Pointing-Pointer Determination of high-temperature phase transitions by X-ray and neutron powder diffraction. Black-Right-Pointing-Pointer Using the symmetry-adapted modes to study the phase transitions.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2010

Crystal structure and substrate specificity of the [beta]-ketoacyl-acyl carrier protein synthase III (FabH) from Staphylococcus aureus

{beta}-Ketoacyl-ACP synthase III (FabH), an essential enzyme for bacterial viability, catalyzes the initiation of fatty acid elongation by condensing malonyl-ACP with acetyl-CoA. We have determined the crystal structure of FabH from Staphylococcus aureus, a Gram-positive human pathogen, to 2 {angstrom} resolution. Although the overall structure of S. aureus FabH is similar to that of Escherichia coli FabH, the primer binding pocket in S. aureus FabH is significantly larger than that present in E. coli FabH. The structural differences, which agree with kinetic parameters, provide explanation for the observed varying substrate specificity for E. coli and S. aureus FabH. The rank order of activity of S. aureus FabH with various acyl-CoA primers was as follows: isobutyryl- > hexanoyl- > butyryl- > isovaleryl- >> acetyl-CoA. The availability of crystal structure may aid in designing potent, selective inhibitors of S. aureus FabH.

36 MATERIALS SCIENCE↗
DOE OSTI2010

Two inorganic-organic hybrid materials based on polyoxometalate anions and methylene blue: Preparations, crystal structures and properties

Two novel inorganic-organic hybrid materials based on an organic dye cation methylene blue (MB) and Lindqvist-type POM polyanions, [C{sub 22}H{sub 18}N{sub 3}S]{sub 2}Mo{sub 6}O{sub 19} 2DMF (1) and [C{sub 22}H{sub 18}N{sub 3}S]{sub 2}W{sub 6}O{sub 19} 2DMF (2) were synthesized under ambient conditions and characterized by CV, IR spectroscopy, solid diffuse reflectance spectrum, UV-vis spectra in DMF solution, luminescent spectrum and single crystal X-ray diffraction. Crystallographic data reveal that compounds 1 and 2 are isostructural and both crystallize in the triclinic space group P1-bar . Their crystal structures present that the layers of organic molecules and inorganic anions array alternatively, and there exist strong {pi}...{pi} stacking interactions between dimeric MB cations and near distance interactions among organic dye cations, Lindqvist-type POM polyanions and DMF molecules. The solid diffuse reflectance spectra and UV-vis spectra in DMF solution appear new absorption bands ascribed to the charge-transfer transition between the cationic MB donor and the POM acceptors. Studies of the photoluminescent properties show that the formation of 1 and 2 lead to the fluorescence quenching of starting materials. -- Graphical abstract: Their crystal structures present that the layers of organic molecules and inorganic anions array alternatively, and there exist strong {pi}...{pi} stacking interactions between dimeric MB cations. Display Omitted

36 MATERIALS SCIENCE↗
DOE OSTI2014

Crystal structure and luminescence properties of a novel red-emitting phosphor BaAlBO{sub 3}F{sub 2}:Eu{sup 3+}

A series of novel red-emitting phosphors BaAlBO{sub 3}F{sub 2}:xEu{sup 3+} (0.001≤x≤0.08) were first synthesized via a high temperature solid-state reaction. X-ray diffraction and photoluminescence spectroscopy were used to characterize the crystal structure and photoluminescence properties of the phosphor, respectively. The phosphor can be effectively excited with a 395 nm light, and shows a dominant {sup 5}D{sub 0}−{sup 7}F{sub 2} emission with chromatic coordination of 0.628 and 0.372. The optimal doping concentration is about 0.04. Rietveld refinement results and the luminescence behavior of Eu{sup 3+} indicate that the Eu{sup 3+} ion occupies a C{sub 3} symmetry site, and the host BaAlBO{sub 3}F{sub 2} has a hexagonal structure with P-6 space group. In addition, the phosphor could be a potential candidate as red-emitting phosphor for application in white light-emitting diode. - Graphical abstract: The luminescence behavior and Rietveld refinement of BaAlBO{sub 3}F{sub 2}:Eu{sup 3+} indicate that the red-emitting phosphor has potential application in white LED and the host has a hexagonal structure with P-6 space group. - Highlights: • A novel red-emitting phosphor BaAlBO{sub 3}F{sub 2}:Eu{sup 3+} is first synthesized. • The crystal structure of BaAlBO{sub 3}F{sub 2} is confirmed. • The phosphor shows potential application in white LED.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2016

Crystal structures and magnetic properties of polyethylene glycol (PEG-4000) and silica-encapsulated nickel ferrite (NiFe{sub 2}O{sub 4}) nanoparticles

Crystal structures and magnetic properties of polyethylene glycol (PEG-4000) and silica encapsulated nickel ferrite (NiFe{sub 2}O{sub 4}) nanoparticles comparable sizes have been studied in detail. NiFe{sub 2}O{sub 4} were prepared by co-precipitation methods. Crystalline size is 4.8 ± 0.2 nm became 1.6 ± 0.1 nm and 10.6 ± 0.3 nm after encapsulated PEG-4000 and silica, respectively. Transmission electron microscopy (TEM) showed that encapsulated PEG-4000 and silica decreased agglomeration, controlled shape of nanoparticles more spherical and dispersed. Coercivity of NiFe{sub 2}O{sub 4} was 46.2 Oe and then increased after encapsulated PEG-4000 to 47.8 Oe can be related to the multi-domains of NiFe{sub 2}O{sub 4} as influence the crystalline size was decreased. Meanwhile, after encapsulated silica, coercivity of NiFe{sub 2}O{sub 4} became 93 Oe as influence the crystalline size was increased at single-domains due to its strong shape anisotropy. Magnetization value decreased from 5.7 emu/g to 5.3 emu/g and 3.6 emu/g after encapsulated PEG-4000 and silica, respectively. The remanent magnetization showed decreasing when saturation magnetization decreased, and conversely. However, it also depends on presence of α-Fe{sub 2}O{sub 3} phases and their material non magnetic of encapsulating. Based on the result, The magnetic properties exhibit a strong dependence on the crystalline size as influence PEG-4000 and silica encapsulated NiFe{sub 2}O{sub 4} nanoparticles.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2015

Synthesis, single crystal structure and energy optimization of a multicomponent salt of imidazole and tetrabromoterepthalic acid

Single crystal of a multicomponent salt (IMTBTP) of imidazole with tetrabromoterepthalic acid has been synthesized by slow evaporation method at room temperature. The crystal structure of the salt has been determined by single crystal x-ray diffraction technique. The supramolecular structure analysis reveals that the multicomponent salt is formed by noncovalent hydrogen bonding interaction and Br···π interaction. The energy optimization and HOMO-LUMO energy gap calculation have been carried out by Density Functional Theory.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2015

Study of the crystal structure of silicon nanoislands on sapphire

The results of studies of the crystal structure of silicon nanoislands on sapphire are reported. It is shown that the principal defects in silicon nanoislands on sapphire are twinning defects. As a result of the formation of such defects, different crystallographic orientations are formed in silicon nanoislands on sapphire. In the initial stages of the molecular-beam epitaxy of silicon on sapphire, there are two basic orientations: the (001) orientation parallel to the surface and the (001) orientation at an angle of 70° to the surface.

36 MATERIALS SCIENCE↗
DOE OSTI2012

The co-crystal structure of ubiquitin carboxy-terminal hydrolase L1 (UCHL1) with a tripeptide fluoromethyl ketone (Z-VAE(OMe)-FMK)

UCHL1 is a 223 amino acid member of the UCH family of deubiquitinating enzymes (DUBs), found abundantly and exclusively expressed in neurons and the testis in normal tissues. Two naturally occurring variants of UCHL1 are directly involved in Parkinson's disease (PD). Not only has UCHL1 been linked to PD, but it has oncogenic properties, having been found abnormally expressed in lung, pancreatic, and colorectal cancers. Although inhibitors of UCHL1 have been described previously the co-crystal structure of the enzyme bound to any inhibitor has not been reported. Herein, we report the X-ray structure of UCHL1 co-crystallized with a peptide-based fluoromethylketone inhibitor, Z-VAE(OMe)-FMK (VAEFMK) at 2.35 {angstrom} resolution. The co-crystal structure reveals that the inhibitor binds in the active-site cleft, irreversibly modifying the active-site cysteine; however, the catalytic histidine is still misaligned as seen in the native structure, suggesting that the inhibitor binds to an inactive form of the enzyme. Our structure also reveals that the inhibitor approaches the active-site cleft from the opposite side of the crossover loop as compared to the direction of approach of ubiquitin's C-terminal tail, thereby occupying the P1{prime} (leaving group) site, a binding site perhaps used by the unknown C-terminal extension of ubiquitin in the actual in vivo substrate(s) of UCHL1. This structure provides a view of molecular contacts at the active-site cleft between the inhibitor and the enzyme as well as furnishing structural information needed to facilitate further design of inhibitors targeted to UCHL1 with high selectivity and potency.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2013

4-Hydroxy-N′-[(1E)-1-(4-methylphenyl)ethylidene]benzohydrazide: Synthesis, crystal structure, and spectroscopic studies

The titled compound has been synthesized by reaction of 4′-methylacetophenon with 4-hydrox-ybenzohydrazide in presence of catalytic amount of glacial acetic acid. The compound is characterized by elemental analysis, IR, {sup 1}H NMR, {sup 13}C NMR and UV-visible spectra. The crystal structure was determined by X-ray diffraction method. Both X-ray data and NMR spectra indicate that the molecule exists in a trans configuration with respect to the C=N bond. The observation of strong ν(C=O) peak in IR spectra of the aroylhydrazone compound suggests that it is in keto form in solid state. X-ray diffraction results confirm this suggestion. In the crystal structure, there are N-H...O and O-H...O hydrogen bonds and weak C-H...π interaction.

36 MATERIALS SCIENCE↗
DOE OSTI2015

Effects of aluminum substitution on the crystal structure and magnetic properties in Zn{sub 2}Y-type hexaferrites

Crystal structure and magnetic properties of multiferroic Y-type hexaferrites Ba{sub 0.5}Sr{sub 1.5}Zn{sub 2}(Fe{sub 1−x}Al{sub x}){sub 12}O{sub 22} (x = 0, 0.04, 0.08, and 0.12) were investigated. The Z- and M-type impurity phases decrease with increasing Al content, and the pure phase samples can be obtained by modulating Al-doping. Lattice distortion exists in Al-doped samples due to the different radius of Al ion (0.535 Å) and Fe ion (0.645 Å). The microstructural morphologies show that the hexagonal shape grains can be observed in all the samples, and grain size decreases with increasing Al content. As for magnetic properties of Ba{sub 0.5}Sr{sub 1.5}Zn{sub 2}(Fe{sub 1−x}Al{sub x}){sub 12}O{sub 22}, there exist rich thermal- and field-driven magnetic phase transitions. Temperature dependence of zero-field cooling magnetization curves from 5 K to 800 K exhibit three magnetic phase transitions involving conical spin phase, proper-screw spin phase, ferromagnetic phase, and paramagnetic phase, which can be found in all the samples. Furthermore, the phase-transition temperatures can be modulated by varying Al content. In addition, four kinds of typical hysteresis loops are observed in pure phase sample at different temperatures, which reveal different magnetization processes of above-motioned magnetic spin structures. Typically, triple hysteresis loops in low magnetic field range from 0 to 0.5 T can be observed at 5 K, which suggests low-field driven magnetic phase transitions from conical spin order to proper-screw spin order and further to ferrimagnetic spin order occur. Furthermore, the coercive field (H{sub C}) and the saturation magnetization (M{sub S}) enhance with increasing Al content from x = 0 to 0.08, and drop rapidly at x = 0.12, which could be attribute to that in initial Al-doped process the pitch of spin helix increases and therefore magnetization enhances, but conical spin phase eventually collapses in higher-concentration Al-doping.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗