Small-angle X-ray Scattering Analysis Research Articles

The plant nucleoplasmin AtFKBP43 needs its extended arms for histone interaction

The nucleoplasmin family of histone chaperones is a key player in governing the dynamic architecture of chromatin, thereby regulating various DNA-templated processes. The crystal structure of the N-terminal domain of Arabidopsis thaliana FKBP43 (AtFKBP43), an FK506-binding immunophilin protein, revealed a characteristic nucleoplasmin fold, thus confirming it to be a member of the FKBP nucleoplasmin class. Small-Angle X-ray Scattering (SAXS) analyses confirmed its pentameric nature in solution, and additional studies confirmed the nucleoplasmin fold to be highly stable. Unlike its homolog AtFKBP53, the AtFKBP43 nucleoplasmin core domain could not interact with histones and required the acidic arms, C-terminal to the core, for histone association. However, SAXS generated low-resolution envelope structure, ITC, and AUC results revealed that an AtFKBP43 pentamer with C-terminal extensions interacts with H2A/H2B dimer and H3/H4 tetramer in an equimolar ratio, like AtFKBP53. Put together, AtFKBP43 belongs to a hitherto unreported subclass of FKBP nucleoplasmins that requires the C-terminal acidic stretches emanating from the core domain for histone interaction.

Crystallographic and Small Angle X-ray Scattering Analyses Provide New Mechanistic Insight into the Protein Quality Control System by the ER-Resident Oxidoreductases and their Upstream Enzymes

Crystallographic and Small Angle X-ray Scattering Analyses Provide New Mechanistic Insight into the Protein Quality Control System by the ER-Resident Oxidoreductases and their Upstream Enzymes

Small-angle X-ray scattering (SAXS) and small-angle neutron scattering (SANS) study on the structure of sodium caseinate in dispersions and at the oil-water interface: Effect of calcium ions

The structure of sodium caseinate particles, as affected by the presence of calcium ions (Ca2+), in aqueous solution and in oil (toluene)-in-water emulsions, was investigated by small-angle X-ray and neutron scattering (SAXS and SANS). SAXS analyses indicated that the sodium caseinate dispersed in water as small particles with electrostatic interactions, which has a radius of gyration (Rg) of ~5 nm and an effective radius (Reff) of ~ 10 nm with an assuming spherical shape. In the presence of Ca2+, the caseinate particles aggregated as large particles with a hydrodynamic diameter > 100 nm as determined by dynamic light scattering. The networks within the large particles were self-assembled from the small Ca2+-cross-linked particles (Rg ~ 6.5–8.0 nm), as probed by SAXS. The fractal-like dimension increased from 2.5 to 3.4 with increasing protein and CaCl2 concentrations, suggesting a denser structure. The integrity of the caseinate particles at the oil-water interface was enhanced by Ca2+ cross-linking, as observed by transmission electron microscopy. The oilwater interface stabilised by Ca2+-cross-linked caseinate particles was ~ 30 nm thick, six times thicker than that stabilised by sodium caseinate (~ 5 nm) as analysed by SANS with contrast variation technique. Quantifying the structure of sodium caseinate in an aqueous solution and at the oil-water interface provides valuable insights for designing new casein-based functional materials.

Synthesis of cholesterol containing unsymmetrical dimers: a new series of liquid crystals

ABSTRACT We report an efficient and practical procedure for the synthesis of cholesterol containing unsymmetrical liquid crystals dimers. Liquid crystalline and thermal properties were studied by POM, TGA, DSC, and SAXS analysis. All final products (3a-d) presented liquid crystal properties. The presence of smectic (compounds 3a, 3b, and 3d) and chiral nematic (3 c) mesophases evidenced by polarised optical microscopy (POM) and further confirmed by small-angle X-ray scattering (SAXS) analyses. The compound 3 c remains supercooled until room temperature and presented enantiotropic mesomorphism at a low temperature. This characteristic of organisation and mesomorphism at room temperature makes compound 3 c an ideal candidate for technological applications. The SAXS analyses further suggest possibly the presence of smectic clusters within the nematic liquid crystalline phase. All compounds presented high thermal stability at around 300°C when tested for their thermal properties. The highest occupied molecular orbital (HOMO) energies were estimated from cyclic voltammetry (CV) and used together with the optical absorption measurements to determine the band gap and lowest unoccupied molecular orbital (LUMO) energies. The values obtained were: HOMO (–5.81 to – 6.03 eV), LUMO (–1.53 to – 2.12 eV), and band gap (3.88 to 4.28 eV).

Stabilization by Nano Spray Dryer of Pioglitazone Polymeric Nanosystems: Development, In Vivo, Ex Vivo and Synchrotron Analysis.

Pioglitazone-loaded PLGA-PEG nanoparticles (NPs) were stabilized by the spray drying technique as an alternative to the treatment of ocular inflammatory disorders. Pioglitazone-NPs were developed and characterized physiochemically. Interaction studies, biopharmaceutical behavior, ex vivo corneal and scleral permeation, and in vivo bioavailability evaluations were conducted. Fibrillar diameter and interfibrillar corneal spacing of collagen was analyzed by synchrotron X-ray scattering techniques and stability studies at 4 °C and was carried out before and after the spray drying process. NPs showed physicochemical characteristics suitable for ocular administration. The release was sustained up to 46 h after drying; ex vivo corneal and scleral permeation profiles of pioglitazone-NPs before and after drying demonstrated higher retention and permeation through cornea than sclera. These results were correlated with an in vivo bioavailability study. Small-angle X-ray scattering (SAXS) analysis did not show a significant difference in the organization of the corneal collagen after the treatment with pioglitazone-NPs before and after the drying process, regarding the negative control. The stabilization process by Nano Spray Dryer B-90 was shown to be useful in preserving the activity of pioglitazone inside the NPs, maintaining their physicochemical characteristics, in vivo bioavailability, and non-damage to corneal collagen function after SAXS analysis was observed.

Injection vs micro-injection molding of nano-particle filled polyamide 6: Moldability and structuring

In this work, the moldability via micro-injection molding (μIM) of nano-filled polyamide 6 (PA6) based systems and the microstructural characteristics of the micro-injected parts were investigated and compared to those observed via traditional injection molding (IM). Two types of nano-fillers, different in nature and geometry, were examined, namely carbon nanotubes and silicate layers. The presence of nano-fillers did not impair the mold replication capability of PA6 in the μIM process. A micro-rib and a standard dumbbell specimen for tensile tests were used as reference micro- and macro-injected part, respectively. Transmission Electron Microscopy, Wide and Small Angle X-ray Scattering and Differential Scanning Calorimetry analyses showed that, due to the different thermomechanical histories during μIM and IM, the micro- and the macro-parts have different microstructures, influenced also by the filler type. Both nano-filler dispersion and PA6 crystallinity were influenced.

Structural Changes during the Growth of Atomically Precise Metal Oxido Nanoclusters from Combined Pair Distribution Function and Small-Angle X-ray Scattering Analysis.

The combination of in situ pair distribution function (PDF) analysis and small‐angle X‐ray scattering (SAXS) enables analysis of the formation mechanism of metal oxido nanoclusters and cluster–solvent interactions as they take place. Herein, we demonstrate the method for the formation of clusters with a [Bi38O45] core. Upon dissolution of crystalline [Bi6O5(OH)3(NO3)5]⋅3 H2O in DMSO, an intermediate rapidly forms, which slowly grows to stable [Bi38O45] clusters. To identify the intermediate, we developed an automated modeling method, where smaller [BixOy] structures based on the [Bi38O45] framework are tested against the data. [Bi22O26] was identified as the main intermediate species, illustrating how combined PDF and SAXS analysis is a powerful tool to gain insight into nucleation on an atomic scale. PDF also provides information on the interaction between nanoclusters and solvent, which is shown to depend on the nature of the ligands on the cluster surface.

Structural Changes during the Growth of Atomically Precise Metal Oxido Nanoclusters from Combined Pair Distribution Function and Small‐Angle X‐ray Scattering Analysis

AbstractThe combination of in situ pair distribution function (PDF) analysis and small‐angle X‐ray scattering (SAXS) enables analysis of the formation mechanism of metal oxido nanoclusters and cluster–solvent interactions as they take place. Herein, we demonstrate the method for the formation of clusters with a [Bi38O45] core. Upon dissolution of crystalline [Bi6O5(OH)3(NO3)5]⋅3 H2O in DMSO, an intermediate rapidly forms, which slowly grows to stable [Bi38O45] clusters. To identify the intermediate, we developed an automated modeling method, where smaller [BixOy] structures based on the [Bi38O45] framework are tested against the data. [Bi22O26] was identified as the main intermediate species, illustrating how combined PDF and SAXS analysis is a powerful tool to gain insight into nucleation on an atomic scale. PDF also provides information on the interaction between nanoclusters and solvent, which is shown to depend on the nature of the ligands on the cluster surface.

Single-Crystalline Mesoporous Palladium and Palladium-Copper Nanocubes for Highly Efficient Electrochemical CO 2 Reduction

Single-Crystalline Mesoporous Palladium and Palladium-Copper Nanocubes for Highly Efficient Electrochemical CO ₂ Reduction

Propane selective carbon adsorbents from phenolic resin precursor

Abstract Novel carbon adsorbents for propane/propylene separation, with an unprecedented adsorption selectivity to propane – the minority component – were prepared from a phenolic resin precursor. The preparation conditions of the carbon molecular sieve adsorbents, such as pre-treatment with phosphoric acid; carbonization and post-treatment with propylene, were carefully investigated concerning their role on the separation performance. The best performing sample, MFF_8, was characterized by SEM, FTIR and small-angle X-ray scattering (SAXS). It was concluded that the pre-treatment with phosphoric acid was critical for obtaining the propane/propylene separation performance – adsorption ratio of ca. 2 at 1 bar and 25 °C; this sample was carbonized at 1100 °C and post-treated with propylene during 12 days. SAXS analysis indicates rod-shaped pores for the MFF_8 sample with a bimodal size distribution with averages of 0.4 nm and 3.7 nm, and HRTEM images show a network of earthworm micropores. The adsorption selectivity of this adsorbent to propane was assigned to the shape and size of the pores and the rigidity of propylene compared with propane for worming through the constriction of the ultra-micropores network. To the best knowledge of the authors, this is the first time a carbon molecular sieve (CMS) adsorbent with rod-shaped pores is reported. This new family of CMS adsorbents show great potential for equilibrium and kinetic based separations of adsorbates displaying different worming performances.

"Host in Host" Supramolecular Core-Shell Type Systems Based on Giant Ring-Shaped Polyoxometalates.

Herein, we show how the chaotropic effect arising from reduced molybdate ions in acidified aqueous solution is able to amplify drastically weak supramolecular interactions. Time-resolved Small Angle X-ray Scattering (SAXS) analysis suggests that molybdenum-blue oligomeric species form huge aggregates in the presence of γ-cyclodextrin (γ-CD) which results in the fast formation of nanoscopic {Mo154 }-based host-guest species, while X-ray diffraction analysis reveals that the ending-point of the scenario results in an unprecedented three-component well-ordered core-shell-like motif. A similar arrangement was found by using preformed hexarhenium chalcogenide-type cluster [Re6 Te8 (CN)6 ]4- as exogenous guest. This seminal work brings better understanding of the self-assembly processes in general and gives new opportunities for practical applications in the design of complex multicomponent materials via the simplicity of the non-covalent chemistry.

ASAXS study of the influence of sulfidation conditions and organic additives on sulfide slabs multiscale organization

One of the ways to improve the activity of the sulfide catalysts is to increase the quantity of molybdenum up to contents greater than 15 wt%. For such high Mo contents, the distribution of MoS2 particles is suspected to play an important role in the catalytic activity. A complete description of the active phase is thus required and implies measuring i) the size and stacking distribution of the isolated slabs, ii) the proportion of Mo involved in aggregates or individual slabs, iii) the size of the aggregates. These steps are essential to deeply explain the intrinsic activity of the catalysts. To address this challenge, Anomalous Small-Angle X-ray Scattering (ASAXS) analyses have been performed on different sets of catalysts, prepared with various organic additives and activated either by a gas sulfidation (1 bar, 350 °C,15%H2S/H2) or by real industrial liquid sulfidation (30 bar, 350 °C, H2/gas oil/DMDS). Furthermore, the spent catalysts were also characterized after HDS catalytic test on a real feedstock. The aim of this study was not to elucidate in detail the chemical mechanisms involved when using additives or different sulfidation conditions, but rather to better understand the impact of the microstructural organization on catalytic performances and demonstrate the potential of the ASAXS technique to give new insights on the multi-scale organization of the molybdenum active phase. We thus demonstrate that ASAXS allows to obtain a more detailed description of the slabs compared to TEM and, simultaneously, to identify and quantify the aggregation state of the particles which occurs on high loaded catalysts. The role of the additives is clearly highlighted after liquid sulfidation, as we demonstrate the dispersive effect of triethylene glycol and thioglycolic acid and to a lower extent of citric acid. The slab length and stacking are decreased, as well as the aggregate amount and size. The analysis of the spent catalysts have also revealed the significant evolution of the active phase under HDS reaction conditions. Among other parameters, the aggregate amount appears as a relevant descriptor since a correlation is found with the intrinsic catalytic performances, which suggests an issue of active sites accessibility.

Structure of the Mycobacterium tuberculosis cPknF and conformational changes induced in forkhead-associated regulatory domains.

Mycobacterium tuberculosis (Mtb) has 11 Serine-Threonine Protein Kinases (STPK) that control numerous physiological processes, including cell growth, cell division, metabolic flow, and transcription. PknF is one of the 11 Mtb STPKs that has, among other substrates, two FHA domains (FHA-1 and FHA-2) of the ATP-Binding Cassette (ABC) transporter Rv1747. Phosphorylation in T152 and T210 located in a non-structured linker that connects Rv1747 FHA domains is considerate to be the regulatory mechanism of the transporter. In this work, we resolved the three-dimensional structure of the PknF catalytic domain (cPknF) in complex with the human kinase inhibitor IKK16. cPknF is conserved when compared to other STPKs but shows specific residues in the binding site where the inhibitor is positioned. In addition, using Small Angle X-Ray Scattering analysis we monitored the behavior of the wild type and three FHA-phosphomimetic mutants in solution, and measured the cPknF affinity for these domains. The kinase showed higher affinity for the non-phosphorylated wild type domain and preference for phosphorylation of T152 inducing the rapprochement of the domains and significant structural changes. The results shed some light on the process of regulating the transporter's activity by phosphorylation and arises important questions about evolution and importance of this mechanism for the bacillus.

Human DDX17 Unwinds Rift Valley Fever Virus Non-Coding RNAs.

Rift Valley fever virus (RVFV) is a mosquito-transmitted virus from the Bunyaviridae family that causes high rates of mortality and morbidity in humans and ruminant animals. Previous studies indicated that DEAD-box helicase 17 (DDX17) restricts RVFV replication by recognizing two primary non-coding RNAs in the S-segment of the genome: the intergenic region (IGR) and 5′ non-coding region (NCR). However, we lack molecular insights into the direct binding of DDX17 with RVFV non-coding RNAs and information on the unwinding of both non-coding RNAs by DDX17. Therefore, we performed an extensive biophysical analysis of the DDX17 helicase domain (DDX17135–555) and RVFV non-coding RNAs, IGR and 5’ NCR. The homogeneity studies using analytical ultracentrifugation indicated that DDX17135–555, IGR, and 5’ NCR are pure. Next, we performed small-angle X-ray scattering (SAXS) experiments, which suggested that DDX17 and both RNAs are homogenous as well. SAXS analysis also demonstrated that DDX17 is globular to an extent, whereas the RNAs adopt an extended conformation in solution. Subsequently, microscale thermophoresis (MST) experiments were performed to investigate the direct binding of DDX17 to the non-coding RNAs. The MST experiments demonstrated that DDX17 binds with the IGR and 5’ NCR with a dissociation constant of 5.77 ± 0.15 µM and 9.85 ± 0.11 µM, respectively. As DDX17135–555 is an RNA helicase, we next determined if it could unwind IGR and NCR. We developed a helicase assay using MST and fluorescently-labeled oligos, which suggested DDX17135–555 can unwind both RNAs. Overall, our study provides direct evidence of DDX17135–555 interacting with and unwinding RVFV non-coding regions.

Carbonaceous Materials Investigated by Small-Angle X-ray and Neutron Scattering

Carbonaceous nanomaterials have become important materials with widespread applications in battery systems and supercapacitors. The application of these materials requires precise knowledge of their nanostructure. In particular, the porosity of the materials together with the shape of the pores and the total internal surface must be known accurately. Small-angle X-ray scattering (SAXS) and small-angle neutron scattering (SANS) present the methods of choice for this purpose. Here we review our recent investigations using SAXS and SANS. We first describe the theoretical basis of the analysis of carbonaceous material by small-angle scattering. The evaluation of the small-angle data relies on the powerful concept of the chord length distribution (CLD) which we explain in detail. As an example of such an evaluation, we use recent analysis by SAXS of carbide-derived carbons. Moreover, we present our SAXS analysis on commercially produced activated carbons (ACN, RP-20) and provide a comparison with small-angle neutron scattering data. This comparison demonstrates the wealth of additional information that would not be obtained by the application of either method alone. SANS allows us to change the contrast, and we summarize the main results using different contrast matching agents. The pores of the carbon nanomaterials can be filled gradually by deuterated p-xylene, which leads to a precise analysis of the pore size distribution. The X-ray scattering length density of carbon can be matched by the scattering length density of sulfur, which allows us to see the gradual filling of the nanopores by sulfur in a melt-impregnation procedure. This process is important for the application of carbonaceous materials as cathodes in lithium/sulfur batteries. All studies summarized in this review underscore the great power and precision with which carbon nanomaterials can be analyzed by SAXS and SANS.

Systematical study of multi-walled carbon nanotube nanofluids based disposed transformer oil

In this paper, the electrical, dielectric, Raman and small angle X-ray scattering (SAXS) structure behavior of disposed transformer oil in the presence of multi-walled carbon nanotube (MWCNT) were systematically tested to verify their versatility for preparing better alternative transformer oil in future. MWCNT nanofluids are prepared using a two-step method with concentrations ranging from 0.00 to 0.02 g/L. The test results reveal that 0.005 g/L concentration possesses the most optimum performance based on the electrical (AC breakdown and lightning impulse) and dielectric (permittivity, dissipation factor and resistivity) behavior. According to the trend of AC breakdown strength and lightning impulse pattern, there were 212.58% and 40.01% enhancement indicated for 0.005 g/L concentration compared to the disposed transformer oil. The presence of MWCNT also yielding to the decrement of dissipation factor, increased on permittivity and resistivity behavior of disposed transformer oil which reflected to the performance of electrical properties. Furthermore, it is found that these features correlated to the structural properties as systematically verify by Raman and SAXS analysis study.

Effect of 1.5-T and 3.0-T magnetic resonance imaging on the ceramic adhesion and physical properties of prosthetic substructures

Statement of problemMagnetic resonance imaging (MRI) is a cross-sectional imaging technique that is widely used in the detection of pathologies in the head and neck region. However, information is lacking about the effect of MRI imaging on the clinical success of fixed partial dentures (FPDs). PurposeThe purpose of this in vitro study was to analyze the effect of MRI on the physical properties and ceramic adhesion of FPD substructure materials. Material and methodsThree hundred disk (12×1 mm) and 255 rectangular (4×2×2 mm) specimens were prepared with different fabrication techniques for 5 experimental groups: direct metal laser sintering (DMLS) with Co-Cr and Ti; casting with Co-Cr and Ni-Cr; and milling with ZrO2. After ceramic application, the disk specimens were subjected to aging and divided into 3 subgroups (n=20) with exposure to 1.5-T and 3.0-T MRI brain scans for 30 minutes and no exposure (control). The shear bond strength (SBS) of the specimens was measured by using a universal testing machine. The rectangular specimens were exposed to MRI with the same procedure, and the nanostructure of the specimens was analyzed with the small-angle X-ray scattering (SAXS) method to detect the nanoscale structural effects of MRI. The average surface roughness (Ra) and Vickers microhardness (Vh) were also measured for complementary analyses. SBS, Ra, and Vh values were statistically analyzed by 1-way ANOVA and the Tukey honestly significant difference test (α=.05). ResultsThe SBS (MPa) of casting groups (P<.001) and DMLS with the Co-Cr group (P<.05) were significantly affected by MRI exposures. The significant differences were seen on the Ra of casting (P<.001) and DMLS with Co-Cr (P<.05) and Ti (P<.01) groups. Also, the Vh of the casting with Co-Cr (P<.001) and Ni-Cr (P<.01) groups showed significant differences. The SAXS analysis indicated that the physical properties of materials were influenced by MRI exposure. ConclusionsThe results indicated that MRI applications affected the metal-ceramic adhesion of Co-Cr and Ni-Cr dental alloys produced by casting and the DMLS technique.

In Situ Synchrotron X-ray Study of the Mechanical Properties of Pure Mg Produced by Powder Metallurgy

In this study, in situ synchrotron X-ray experiments with wide-angle X-ray scattering (WAXS) and small-angle X-ray scattering (SAXS) detectors were performed on two pure magnesium materials produced by powder metallurgy. According to SAXS analysis, each of the two materials has a porosity of less than 0.5%. Line broadening analysis was performed on diffraction patterns collected by WAXS to analyze the dislocation evolution during material deformation. In both materials, &lt;a&gt;-type dislocation activities dominate the tensile deformation. The influence of grain size and texture on the different tensile behaviors of these two materials is also discussed.

Probing the mechanism of gelation and anion sensing capability of a thiazole based amide gelator: A case study

In priori design of Low Molecular weight Gelators (LMWGs) based on the molecular structure is a challenging task and requires the hierarchy knowledge from single molecule packing to a supramolecular assembly in gelator fibers. A simple strategy to select and probe the packing of a molecule from a crystalline state to a semi solid gel state was undertaken in a Thiazole based amide, undecaneamido thiazole (Thz-9). The novel approach to select the promising molecule with gelation property was made using Small Angle Neutron Scattering (SANS) and Small Angle X-ray Scattering (SAXS) analysis of solid samples. Based on the preliminary examination of SANS/SAXS studies Thz-9 molecule was selected and subjected to study the packing of molecule in crystalline to a gel state. The sol-gel transition and variation of the molecular diameter of the supramolecular assembly of Thz-9 molecules in the various states were established using temperature dependent SANS study. Efforts were also directed to establish the relationship between the packing of molecules in single crystal structure to packing in xerogel (dried gel) using Powder X-ray Diffraction (PXRD). A potential application of Thz-9 as a fluoride ion sensor with good selectivity and sensitivity was established.

Hexagonal Packing of Nanofibrils in Bombyx mori Silkworm Silk Revealed by Small-angle X-ray Scattering Analysis

Hexagonal Packing of Nanofibrils in Bombyx mori Silkworm Silk Revealed by Small-angle X-ray Scattering Analysis