Rotating-anode X-ray Generator Research Articles

A novel experimental approach for nanostructure analysis: simultaneous small-angle X-ray and neutron scattering.

Exploiting small-angle X-ray and neutron scattering (SAXS/SANS) on the same sample volume at the same time provides complementary nanoscale structural information in two different contrast situations. Unlike an independent experimental approach, the truly combined SAXS/SANS experimental approach ensures the exactness of the probed samples, particularly for in situ studies. Here, an advanced portable SAXS system that is dimensionally suitable for installation in the D22 zone of ILL is introduced. The SAXS apparatus is based on a Rigaku switchable copper/molybdenum microfocus rotating-anode X-ray generator and a DECTRIS detector with a changeable sample-to-detector distance of up to 1.6 m in a vacuum chamber. A case study is presented to demonstrate the uniqueness of the newly established method. Temporal structural rearrangements of both the organic stabilizing agent and organically capped gold colloidal particles during gold nanoparticle growth are simultaneously probed, enabling the immediate acquisition of correlated structural information. The new nano-analytical method will open the way for real-time investigations of a wide range of innovative nanomaterials and will enable comprehensive in situ studies on biological systems. The potential development of a fully automated SAXS/SANS system with a common control environment and additional sample environments, permitting a continual and efficient operation of the system by ILL users, is also introduced.

Influence of Heat Treatment Temperature of Graphene Oxide on the Transport of Charge in Nanocomposites with Pressure Sensitive Paints

The vast majority of polymeric materials are insulators, which limits their application in some areas, such as electronics and sensors, and research is being carried out to increase the conductivity through the insertion of nanocharges, mainly of origin such as graphene and carbon nanotubes. Thus, the change in the electrochemical properties generated in pressure sensitive paints (PSP) was analyzed by adding thermally reduced graphene oxide at two temperatures. Graphite oxide (GrO) was produced by the Hummers method, which was thermally reduced in a Splemby furnace, at temperatures of 400 ºC (752ºF) and 1000 ºC (1832ºF), at a speed of 10 ˚C / min, with a step of 15 minutes. The reduced graphene oxide (rGO) was ultrasonically mixed with the paint UniFIB® UF: 400-470 at a concentration of 4 mg/ml and then dripped 4 times on aeronautical steel and aluminum 2024 electrodes, and dried at room temperature. Crystallographic structures were determined using X-ray diffractometer Panalytical XPertPRO, with a rotating anode X-ray generator working at 5˚≤2θ≤90˚, with Cu monochromatic radiation (0,154 nm) and Fourier Transform Infrared Spectroscopy(FT-IR) using a Perkin Elmer Spectrum Onespectrometer, with transmission by KBr pads technique. Electrochemical Impedance Spectroscopy (EIS) characterization was performed through Autolab PGSTAT 302 potentiostat-galvanostat, using three electrode cell - at work of composite electrode, at auxiliary of Pt mesh; reference of Ag/AgCl. The diffractograms, Figure 1, are similar to those in the literature [1], indicating that rGO was obtained. This can be confirmed by comparing the FTIR spectra of the produced material and commercial rGO, Figure 2, and it was possible to verify the transformation obtained after the heat treatment, when comparing the spectrum of the GrO and rGO, noting the difference in the intensity of the oxygen groups. In addition, it can be seen that the thermal process of 1000 ˚C was more efficient in the removal of oxygen than the 400 ˚C, as indicated by the bands of approximately 1740 cm-1 (- C = O) and 1200 cm-1 (-COC-), whereas in the treatment of 1000 ˚C there was a reduction of both, while in the 400 ˚C the band of 1740 cm-1 was reduced and there was an increase in 1200 cm-1, which shows that the treatment of 400 ˚C was sufficient to transform the less stable (mainly hydroxylic) species of GrO into metastable oxygenated species (carbonyls and alkoxy). For the electrodes produced, it was possible to notice that rGO probably facilitates the locomotion of the electrons in the existing bonds in the paint, and each substrate used has a tendency to donate or receive electrons, which varies according to the type of bond involved. This trend seems to be verified in Nyquist Plot. Table 2 was obtained from them, and made it possible to analyze the electrochemical properties of the double layer formed on the surface of each electrode. The double layer formed on the rGO@Paint composite electrode using rGO annealed at 400 ° C has lower ohmic resistance when tested on both metals. In the case of the one prepared with rGO annealed at 1000 ˚C, the ohmic resistance value doubles in the case of steel and quintuple in the case of Aluminum. This fact demonstrates that rGO with higher degree of oxygen groups generates a greater migration of charge between the obtained electrodes and the electrolyte. The paint insulating character is significantly mitigated after the addition of nanometer powder, but the rGO reduction process can not be performed in order to completely expel the oxygen groups from the paint, since these are probably responsible for the migration of charge between the components of the composite electrode and between this and the electrolyte, as suggested by Duan [2], when analyzing the effect of oxygenated groups on the sensitivity of studied sensor, it was noted the greater the amount of oxygenated groups, the more intense the charge transfer.

Phase imaging using focused polycapillary optics

Conventional radiographic techniques depend on attenuation, which provides low contrast between soft tissues. However, X rays can accumulate large differential phase delays even in weakly absorbing materials. This can produce significantly higher contrast. One technique for taking advantage of phase effects, propagation-based phase imaging, can yield marked edge enhancement but requires spatially coherent intense sources. Microfocus sources have sizes on the order of tens of microns but necessarily are low power and hence require long exposures. In this project, X-ray optical and computational techniques were explored to develop both edge-enhancement and phase imaging using a large spot conventional source. A polycapillary optic was employed to create a small secondary source from a large spot rotating anode X-ray generator. The secondary spot created by the focusing polycapillary optic was 114 µm ± 50 µm. Images of a 1.6 mm polyethylene rod were taken at varying distances from the optic. Edge enhancement was observed with a maximum edge-enhancement-to-noise ratio of 6.5. Insect images were also acquired and analyzed. Phase reconstructions were computed using two different approaches, weak attenuation and phase attenuation duality. Pure phase images were successfully reconstructed from the phase contrast images by employing the weak attenuation model.

Combined optic system based on polycapillary X-ray optics and single-bounce monocapillary optics for focusing X-rays from a conventional laboratory X-ray source

Two combined optic systems based on polycapillary X-ray optics and single-bounce monocapillary optics (SBMO) were designed for focusing the X-rays from a conventional laboratory X-ray source. One was based on a polycapillary focusing X-ray lens (PFXRL) and a single-bounce ellipsoidal capillary (SBEC), in which the output focal spot with the size of tens of micrometers of the PFXRL was used as the “virtual” X-ray source for the SBEC. The other system was based on a polycapillary parallel X-ray lens (PPXRL) and a single-bounce parabolic capillary (SBPC), in which the PPXRL transformed the divergent X-ray beam from an X-ray source into a quasi-parallel X-ray beam with the divergence of sever milliradians as the incident illumination of the SBPC. The experiment results showed that the combined optic systems based on PFXRL and SBEC with a Mo rotating anode X-ray generator with the focal spot with a diameter of 300μm could obtain a focal spot with the total gain of 14,300 and focal spot size of 37.4μm, and the combined optic systems based on PPXRL and SBPC with the same X-ray source mentioned above could acquire a focal spot with the total gain of 580 and focal spot size of 58.3μm, respectively. The two combined optic systems have potential applications in micro X-ray diffraction, micro X-ray fluorescence, micro X-ray absorption near edge structure, full field X-ray microscopes and so on.

A laboratory-based hard x-ray monochromator for high-resolution x-ray emission spectroscopy and x-ray absorption near edge structure measurements.

We report the development of a laboratory-based Rowland-circle monochromator that incorporates a low power x-ray (bremsstrahlung) tube source, a spherically bent crystal analyzer, and an energy-resolving solid-state detector. This relatively inexpensive, introductory level instrument achieves 1-eV energy resolution for photon energies of ∼5 keV to ∼10 keV while also demonstrating a net efficiency previously seen only in laboratory monochromators having much coarser energy resolution. Despite the use of only a compact, air-cooled 10 W x-ray tube, we find count rates for nonresonant x-ray emission spectroscopy comparable to those achieved at monochromatized spectroscopy beamlines at synchrotron light sources. For x-ray absorption near edge structure, the monochromatized flux is small (due to the use of a low-powered x-ray generator) but still useful for routine transmission-mode studies of concentrated samples. These results indicate that upgrading to a standard commercial high-power line-focused x-ray tube or rotating anode x-ray generator would result in monochromatized fluxes of order 10(6)-10(7) photons/s with no loss in energy resolution. This work establishes core technical capabilities for a rejuvenation of laboratory-based hard x-ray spectroscopies that could have special relevance for contemporary research on catalytic or electrical energy storage systems using transition-metal, lanthanide, or noble-metal active species.

Fast SAXS data at home--Your personal SAXS beamline

Small angle X-ray scattering (SAXS) is a useful technique for extracting structural information from biological samples in solution. Our SAXS instrument, the BioSAXS-1000, combines Kratky collimation with confocal optics to achieve maximum X-ray flux on the sample without beam shape corrections. Recently, we offered three new upgrades to the BioSAXS-1000: (1) 2.3 times more flux with the OptiSAXS optic, (2) automatic sample loading, and (3) automatic data analysis. Here, we evaluate the quality of SAXS data collected in short exposure times on the BioSAXS-1000 with these 3 upgrades by using X-rays supplied by an FR-X rotating anode X-ray generator. We measured a concentration series for each of several protein standards (lysozyme, HSA, etc.). Our results show that 1-minute exposures were sufficient to determine the basic structural parameters: radius of gyration, extrapolated intensity at zero angle, and molecular weight. The upgraded BioSAXS-1000 provides a beamline experience in the home laboratory.

In-house simultaneous collection of small-angle X-ray scattering, wide-angle X-ray diffraction and Raman scattering data from polymeric materials

An in-house X-ray scattering system, which can simultaneously measure small-angle X-ray scattering (SAXS) and wide-angle X-ray diffraction (WAXD) data, as well Raman scattering data, has been developed to study the phase transitions of polymeric materials. To date, these types of measurements have been limited to synchrotron radiation. The present system is an in-house SAXS system combined with a WAXD detector and a Raman spectrometer. A rotating-anode X-ray generator and multilayer optic are employed to provide a high-flux X-ray beam. Two two-dimensional hybrid pixel detectors are utilized for the rapid-scan time-resolved SAXS and WAXD measurements. The Raman unit consists of a compact probe with a near-infrared excitation laser operating at a wavelength of 1064 nm. This long-wavelength laser produces less fluorescence than conventional excitation lasers with wavelengths of 532 or 785 nm. The performance of this system was tested by investigating the thermally induced ferroelectric phase transition of vinylidene fluoride–trifluoroethylene (VDF-TrFE) copolymers. It has been demonstrated that the combination of SAXS, WAXD and Raman techniques gives useful information for revealing the relationship between the structural change in the crystal lattice and the morphological change in the lamellar stacking mode in polymer samples of complicated hierarchical structure.

The base of the ribosomal P stalk fromMethanococcus jannaschii: crystallization and preliminary X-ray studies

The lateral P stalk in archaeal/eukaryotic ribosomes and the L12 stalk in bacterial ribosomes play a pivotal role in specific binding to the ribosome and recruiting translational factors during protein biosynthesis. The P stalk consists of the ribosomal proteins L11, P0 and P1. The proteins P0 and P1 form the complex that binds 23S rRNA through the N-terminal domain of the P0 protein. Ribosomal protein L11 binds to the same region of 23S rRNA and together with the protein P0 forms the base of the stalk. The structure of the ribosomal protein L11 from archaea has been solved, but with several missing segments. Here, the preparation and crystallization of a ternary complex consisting of the ribosomal protein L11, the two-domain N-terminal fragment of the ribosomal protein P0 and a specific fragment of 23S rRNA from the archaeon Methanococcus jannaschii are reported. The crystals belonged to the monoclinic space group P2(1), with unit-cell parameters a = 72.4, b = 88.5, c = 95.2 Å, β = 102.2°. A complete diffraction data set has been collected to a resolution of 2.9 Å using an in-house rotating-anode X-ray generator.

Autoproteolytic Activation of a Symbiosis-regulated Truffle Phospholipase A2

Fungal phospholipases are members of the fungal/bacterial group XIV secreted phospholipases A(2) (sPLA(2)s). TbSP1, the sPLA(2) primarily addressed in this study, is up-regulated by nutrient deprivation and is preferentially expressed in the symbiotic stage of the ectomycorrhizal fungus Tuber borchii. A peculiar feature of this phospholipase and of its ortholog from the black truffle Tuber melanosporum is the presence of a 54-amino acid sequence of unknown functional significance, interposed between the signal peptide and the start of the conserved catalytic core of the enzyme. X-ray diffraction analysis of a recombinant TbSP1 form corresponding to the secreted protein previously identified in T. borchii mycelia revealed a structure comprising the five α-helices that form the phospholipase catalytic module but lacking the N-terminal 54 amino acids. This finding led to a series of functional studies that showed that TbSP1, as well as its T. melanosporum ortholog, is a self-processing pro-phospholipase A(2), whose phospholipase activity increases up to 80-fold following autoproteolytic removal of the N-terminal peptide. Proteolytic cleavage occurs within a serine-rich, intrinsically flexible region of TbSP1, does not involve the phospholipase active site, and proceeds via an intermolecular mechanism. Autoproteolytic activation, which also takes place at the surface of nutrient-starved, sPLA(2) overexpressing hyphae, may strengthen and further control the effects of phospholipase up-regulation in response to nutrient deprivation, also in the context of symbiosis establishment and mycorrhiza formation.

Preliminary X-ray crystallographic studies on acetate kinase (AckA) from Salmonella typhimurium in two crystal forms.

Acetate kinase (AckA) catalyzes the reversible transfer of a phosphate group from acetyl phosphate to ADP, generating acetate and ATP, and plays a central role in carbon metabolism. In the present work, the gene corresponding to AckA from Salmonella typhimurium (StAckA) was cloned in the IPTG-inducible pRSET C vector, resulting in the attachment of a hexahistidine tag to the N-terminus of the expressed enzyme. The recombinant protein was overexpressed, purified and crystallized in two different crystal forms using the microbatch-under-oil method. Form I crystals diffracted to 2.70 Å resolution when examined using X-rays from a rotating-anode X-ray generator and belonged to the monoclinic space group C2, with unit-cell parameters a = 283.16, b = 62.17, c = 91.69 Å, β = 93.57°. Form II crystals, which diffracted to a higher resolution of 2.35 Å on the rotating-anode X-ray generator and to 1.90 Å on beamline BM14 of the ESRF, Grenoble, also belonged to space group C2 but with smaller unit-cell parameters (a = 151.01, b = 78.50, c = 97.48 Å, β = 116.37°). Calculation of Matthews coefficients for the two crystal forms suggested the presence of four and two protomers of StAckA in the asymmetric units of forms I and II, respectively. Initial phases for the form I diffraction data were obtained by molecular replacement using the coordinates of Thermotoga maritima AckA (TmAckA) as the search model. The form II structure was phased using a monomer of form I as the phasing model. Inspection of the initial electron-density maps suggests dramatic conformational differences between residues 230 and 300 of the two crystal forms and warrants further investigation.

X-ray structure of a galactose-specific lectin from Spatholobous parviflorous

A galactose-specific seed lectin from Spatholobous parviflorus (SPL) has been purified, crystallized and its X-ray structure solved. It is the first lectin purified and crystallized from the genus Spatholobus (family: Fabaceae). The crystals belong to the space group P1, with a=60.792Å, b=60.998Å, c=78.179Å, α=78.68°, β=88.62°, γ=104.32°. The data were collected at 2.04Å resolution under cryocondition, on a MAR image-plate detector system, mounted on a rotating anode X-ray generator. The coordinates of Dolichos biflorus lectin (1lu1) were successfully used for the structure solution by molecular replacement method. The primary structure of the SPL was not known earlier and it was unambiguously visible in the electron density. S. parviflorus lectin is a hetero-dimeric-tetramer with two alpha and two beta chains of 251 and 239 residues respectively. SPL has two metal ions, Ca2+ and Mn2+, bound to a loop region of each chain. The SPL monomers are in jelly roll form.

Crystallization and preliminary X-ray studies of a galactose-specific lectin from the seeds of Spatholobus parviflorus.

A galactose-specific seed lectin was purified from the legume Spatholobus parviflorus and crystallized using the hanging-drop vapour-diffusion technique. Thecrystals belonged to space group P1, with unit-cell parameters a = 60.998, b=60.792, c = 78.179 Å, α = 101.32, β = 91.38, γ = 104.32°. X-ray diffraction data were collected under cryoconditions (100 K) to a resolution of 2.04 Å using a MAR image-plate detector system mounted on a rotating-anode X-ray (Cu Kα) generator. Molecular replacement using legume-lectin coordinates as a search model gave a tetrameric structure.

Crystallization and preliminary X-ray diffraction analysis of a galactose-specific lectin from the seeds of Butea monosperma.

The galactose-specific lectin from the seeds of Butea monosperma has been crystallized by the hanging-drop vapour-diffusion technique. The crystals belonged to space group P1, with unit-cell parameters a = 78.45, b = 78.91, c = 101.85 Å, α = 74.30, β = 76.65, γ = 86.88°. X-ray diffraction data were collected to a resolution of 2.44 Å under cryoconditions (100 K) using a MAR image-plate detector system mounted on a rotating-anode X-ray generator. Molecular-replacement calculations carried out using the coordinates of several structures of legume lectins as search models indicate that the galactose-specific lectin from B. monosperma forms an octamer.

Development of X‐ray diffractometer for in‐situ observation of thin‐film crystal growth equipped with focusing monochromator

AbstractX‐ray crystal truncation rod scattering measurement is a kind of X‐ray diffraction/scattering measurement, which is a very powerful technique to analyze interface structures quantitatively and non‐destructively. The X‐ray CTR scattering measurement can reveal layer thicknesses, distributions of atoms, surface roughness, and lattice constants at an atomic‐scale. In our previous works, synchrotron radiation (SR) has been utilized as an X‐ray source for the measurement, since it is generally considered that a strong X‐ray is necessary to measure the very weak CTR scattering signal. In this work, using a conventional X‐ray source, i.e., rotating anode X‐ray generator operated at 300 mA and 50 kV, we successfully developed an X‐ray diffractometer that can be used for the X‐ray CTR scattering measurement. The key component was a Johansson monochromator to develop the diffractometer. The Johansson monochromator was utilized both to focus X‐ray at a sample position (to make divergence angle of the incident X‐rays) and to monochromatize Cu‐Kα. By using the Johansson monochromator and a 2D‐detector, a sample was irradiated by a diverging incident X‐ray beam and the scattered X‐ray was detected at the same time. In order to suppress the noise, a Soller slit was introduced. The noise was greatly suppressed and spectrum was drastically improved by using the Soller slit. Without moving the X‐ray source, the sample, nor the detector, a reciprocal space map of a crystal can be obtained by the newly developed diffractometer, and it reduced the measurement time drastically. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Development of a high-brilliance rotating-anode dual-wavelength X-ray generator and multilayer mirror for dual wavelength

Development of a high-brilliance rotating-anode dual-wavelength X-ray generator and multilayer mirror for dual wavelength

Crystal Structure of a Bony Fish β2-Microglobulin: INSIGHTS INTO THE EVOLUTIONARY ORIGIN OF IMMUNOGLOBULIN SUPERFAMILY CONSTANT MOLECULES

Crystal Structure of a Bony Fish β2-Microglobulin: INSIGHTS INTO THE EVOLUTIONARY ORIGIN OF IMMUNOGLOBULIN SUPERFAMILY CONSTANT MOLECULES

The Connection between the Presence of Melanoma and Changes in Fibre Diffraction Patterns

An accurate diagnosis of melanomas at an early stage correlates directly with a better prognosis. However the incidence of melanoma is still increasing along with the number of related deaths. Melanoma cells grow extremely fast, with the result that many patients present after metastasis has occurred, too late for effective treatment. This paper describes the changes in the fibre diffraction patterns of skin that indicate the presence of a melanoma. Identification of these changes would provide an alternative early low-cost, reliable diagnostic test which could be conducted on a regular basis in local radiology facilities using rotating anode X-ray generators or as a mass screening test using suitable small angle x-ray beam-lines at synchrotrons.

Properties of the Thioredoxin Fold Superfamily Are Modulated by a Single Amino Acid Residue

The ubiquitous thioredoxin fold proteins catalyze oxidation, reduction, or disulfide exchange reactions depending on their redox properties. They also play vital roles in protein folding, redox control, and disease. Here, we have shown that a single residue strongly modifies both the redox properties of thioredoxin fold proteins and their ability to interact with substrates. This residue is adjacent in three-dimensional space to the characteristic CXXC active site motif of thioredoxin fold proteins but distant in sequence. This residue is just N-terminal to the conservative cis-proline. It is isoleucine 75 in the case of thioredoxin. Our findings support the conclusion that a very small percentage of the amino acid residues of thioredoxin-related proteins are capable of dictating the functions of these proteins.

Crystallization and preliminary crystallographic study of the phosphoglucose isomerase from Bacillus subtilis.

Crystallization and preliminary crystallographic analysis of the phosphoglucose isomerase from a Bacillus subtilis native strain were carried out. The crystals belonged to the monoclinic space group C2, with unit-cell parameters a = 145.7, b = 136.0, c = 109.1 A, beta = 119.4 degrees . The diffraction quality of the crystal was significantly improved from 2.4 A to greater than 1.9 A resolution by using the in situ flash-annealing method. A 98% complete data set with an overall R(merge) of 4.6% was collected using an R-AXIS IV(++) image-plate system and a copper rotating-anode X-ray generator. The crystals contained four molecules per asymmetric unit and the predicted solvent content and the Matthews coefficient (V(M)) were 46.8% and 2.3 A(3) Da(-1), respectively. Structure determination by the molecular-replacement method provided a reasonable solution for model building.

Observation on structure in the surface region of cocoa butter, POP, SOS and POS by X-ray diffraction

Cocoa butter, prepared from ground roasted cacao beans, has six polymorphisms characterized by different melting points in thermal analysis. It is known to consist of several oils and fats, e.g., POP (sn-1,3-dipalmitoyl-2-oleoylglycerol), SOS (sn-1,3-dialmitoyl2-stearoyl-glycerol) and POS (1,3-rac-palmitoylstearoyl-2oleoylglycerol), etc. Since there is some resemblance in molecular structure among them, POP, SOS and POS exhibit six or five polymorphisms like cocoa butter. They are also known to acquire stable structures throughout phase transformation via quasi-stable polymorphisms. In the present study, we observe structures in surface region to a depth of 10nm from the surface and those of thin films of polymorphisms of POP, SOS, POS and natural cocoa butter by surface-sensitive X-ray diffraction techniques. The aim of our research is to clarify the peculiar molecular interactions and structures emerging only in the surface and thin films, which would also serve as basic information on melting and oxidation of chocolate. X-ray reflectivity (XR) and grazing incidence X-ray diffraction (GIXD) were exploited with high precision diffract meters on rotating anode X-ray generators (SLX2000+UltraX, TTR-450, Rigaku Co.). Thin films on Si (100) were prepared by spin-coating method with acetone as a solvent. For cocoa butter, uniform layers were easily formed by annealing, yet dewetted layers are obtained for some oils even after the annealing. A strong surface-induced preferred orientation is shown for all the samples, indicating anisotropy in intermolecular interaction. Furthermore, a distinct transformation from a double-layer structure to a single-layer structure is observed. We consider that those structures might correspond to smectic phases of liquid crystals.