Small-Angle Scattering Study Research Articles

Evolution of the Ligand Shell Around Small ZnO Nanoparticles During the Exchange of Acetate by Catechol: A Small Angle Scattering Study

AbstractThe core‐shell structure of colloids surrounded by ligands is of great importance for their later application as it can significantly alter the chemical and physical properties of the nanoparticles (NPs). A combination of small angle X‐ray and neutron scattering (SAXS/SANS) in the native solution with additional ex situ measurements (titration‐UV) was applied to study the NP/ligand interface of ZnO NPs after functionalization with catechol derivatives. Based on SAXS data, it was found that within the multimodal particle size distribution the fraction of agglomerates is shifted to smaller sizes and nearly disappeared upon the binding of ethyl 3,4‐dihydroxybenzoate (CAT) molecules. This is ascribed to improved stabilization at the primary particle level by CAT molecules. By combining the neutron scattering contrast with the input of bound CAT molecules from a previously developed titration‐UV method, the heterogeneous composition of the ligand shell became accessible for the first time.

Erratum to: “Structural Analysis of Aluminum Oxyhydroxide Aerogel: Small Angle Scattering Studies” [Journal of Surface Investigation: X-ray, Synchrotron and Neutron Techniques 12, 296 (2018)

The title of the article should read as follows: Structural Analysis of Aluminum Oxyhydroxide Aerogel: Small Angle Scattering Studies

Effects of Macromolecular Crowding on the Structure of a Protein Complex: A Small-Angle Scattering Study of Superoxide Dismutase

Macromolecular crowding can alter the structure and function of biological macromolecules. We used small-angle scattering to measure the effects of macromolecular crowding on the size of a protein complex, SOD (superoxide dismutase). Crowding was induced using 400 MW PEG (polyethylene glycol),TEG (triethylene glycol), α-MG (methyl-α-glucoside), and TMAO (trimethylamine n-oxide). Parallel small-angle neutron scattering and small-angle x-ray scattering allowed us to unambiguously attribute apparent changes in radius of gyration to changes in the structure of SOD. For a 40% PEG solution, we find that the volume of SOD was reduced by 9%. Considering the osmotic pressure due to PEG, this deformation corresponds to a highly compressible structure. Small-angle x-ray scattering done in the presence of TEG suggests that for further deformation—beyond a 9% decrease in volume—the resistance to deformation may increase dramatically.

Small Angle Scattering Study of the Structure and Organization of RNAs and Protein of Brome Mosaic Virus (BMV) Capsid Protein

Brome mosaic virus (BMV) viron is a model system that has a small icosahedral capsid protein (CP) shell. It is well known that BMV is plant virus which is a member of the alpha virus-like superfamily group. These viruses have genetic material and nucleic acids (RNA) with a segmented positive-strand RNA that offers high levels of RNA synthesis and virus production in plants. BMV CP tightly regulates the packaging of its RNAs into the inner core of the capsid while maintaining an outer protein shell coat. Small angle neutron scattering (SANS) and small angle X- ray scattering (SAXS) were applied to study the size, shape and protein-RNAs organization of BMV CP. BMV capsid protein and buffer solution containing a D2O/H2O mixture was used to enhance the contrast of the material for neutron scattering measurements. The pair distance distribution P(r) of BMV CP from the indirect Fourier transform of scattering spectrum was able to illustrate the differences in the distribution of materials, signifying RNAs packing, and protein in the BMV CP. The extracted parameter from P(r) shows that the BMV CP is about 260Å in diameter and is composed of RNA with ∼ 74Å core radiuses and coated protein shell of thickness 56Å. The contribution of RNAs core, protein shell was estimated by simulation. The contribution due to interference of core and shell called cross term was also extracted from simulation.

Small-Angle X-ray and neutron scattering from diamond single crystals

Results of Small-Angle Scattering study of diamonds with various types of point and extended defects and different degrees of annealing are presented. It is shown that thermal annealing and/or mechanical deformation cause formation of nanosized planar and three-dimensional defects giving rise to Small-Angle Scattering. The defects are often facetted by crystallographic planes 111, 100, 110, 311, 211 common for diamond. The scattering defects likely consist of clusters of intrinsic and impurity-related defects; boundaries of mechanical twins also contribute to the SAS signal. There is no clear correlation between concentration of nitrogen impurity and intensity of the scattering.

Mono- and Trivalent Ions around DNA: A Small-Angle Scattering Study of Competition and Interactions

The presence of small numbers of multivalent ions in DNA-containing solutions results in strong attractive forces between DNA strands. Despite the biological importance of this interaction, e.g., DNA condensation, its physical origin remains elusive. We carried out a series of experiments to probe interactions between short DNA strands as small numbers of trivalent ions are included in a solution containing DNA and monovalent ions. Using resonant (anomalous) and nonresonant small angle x-ray scattering, we coordinated measurements of the number and distribution of each ion species around the DNA with the onset of attractive forces between DNA strands. DNA-DNA interactions occur as the number of trivalent ions increases. Surprisingly good agreement is found between data and size-corrected numerical Poisson-Boltzmann predictions of ion competition for non- and weakly interacting DNAs. We also obtained an estimate for the minimum number of trivalent ions needed to initiate DNA-DNA attraction.

New Insight into Hierarchical Structures of Carbon Black Dispersed in Polymer Matrices: A Combined Small-Angle Scattering Study

Using a combined ultra-small-angle and small-angle scattering (CSAS) method of neutrons and X-rays, we investigated hierarchical structures of carbon black (CB) highly loaded in polyisoprene (PI) and poly(styrene-random-butadiene) copolymer (SBR) under mechanical field (defined respectively as CB/PI and CB/SBR) as well as in toluene under a sonic field (defined as CB/toluene). In order to analyze each structure level comprising the hierarchical structures of CB from the CSAS profiles, we employed the unified Guinier/power-law approach proposed by Beaucage (J. Appl. Cryst. 1995, 28, 717). Furthermore, in order to extract not only sizes but also shapes of the structure elements, we developed a modified approach, in which the Guinier scattering function utilized in the Beaucage approach was replaced by a form factor of the corresponding structure. Comparison of the scattering profiles from CB/PI and CB/SBR with CB/toluene clarified that (i) the smallest structure elements of CB (that further form mass-fracta...

Biological Systems as Nanoreactors: Anomalous Small-Angle Scattering Study of the CdS Nanoparticle Formation in Multilamellar Vesicles

The formation of cadmium sulfide (CdS) particles in the gaps between the layers of the multilamellar vesicles is described, introducing a new pathway in the preparation of nanometer-scale particles. The in situ structural characterization of both the CdS particles and the vesicles as a reaction medium was performed in the early and final states of the process by using anomalous small-angle X-ray scattering (ASAXS) and freeze-fracture methods. The ASAXS method provides the separation of the scattering of nanoparticles present in a small amount, whereby the monitoring of their formation and growth in the whole time range of manufacturing has become possible.

Small‐angle Scattering Studies of Adsorption and of Capillary Condensation in Porous Solids

AbstractSmall‐angle scattering (SAS) studies are reviewed of adsorption and capillary condensation of water, hydrocarbons and halogenated hydrocarbons near room temperature, and of nitrogen at 78 K in some mesoporous solids, mainly silicas. The theory needed for the interpretation of SAS data is briefly covered. Calculations of the scattered intensity I(q) for a model porous medium show that I(q) depends markedly on the film thickness t. Adsorption and capillary condensation of nitrogen at 78 K in mesoporous silicas was studied by use of in situ SANS, and t as function of the relative pressure P/Ps was estimated. Adsorption of N2 in defects within the silica skeleton at P/Ps<0.1 lead to a significant increase in I(q). Isolated vapor bubbles in capillary condensed nitrogen in a Gelsil® appeared on adsorption near saturation of the pore system. The kinetics of capillary condensation and of drainage were followed. Power law scattering at low q indicated the formation of ramified clusters of voids on drainage of liquid nitrogen from the xerogel Gelsil®. Similar clusters were observed on drainage of water from Vycor® glass. Provided the clusters indicate a percolation process, the desorption branch should not be used for the estimation of a pore size distribution for materials with networked pores. The adsorptive smoothing by benzene was observed of a rough interface in a controlled pore glass.

D-56 Time-Resolved Small Angle Scattering Studies of Alignment of Block Copolymer Solutions Induced by Electric Fields

D-56 Time-Resolved Small Angle Scattering Studies of Alignment of Block Copolymer Solutions Induced by Electric Fields

Small-Angle Scattering Study of Mesoscopic Structures in Charged Gel and Their Evolution on Dehydration

Mesoscopic structures, with length scales ∼102 Å, were investigated by small-angle X-ray and neutron scattering (SAXS and SANS) in several N-isopropylacrylamide−sodium acrylate (NIPA−SA) copolymeric hydrogels with varying [NIPA]/[SA] ratios and water contents. The SAXS experiments reveal that, depending upon the [NIPA]/[SA] ratio, the dehydrated NIPA−SA gel shows two mesoscopic structures: one consists of randomly distributed SA-rich islands in NIPA matrix, while the other is a microphase-separated structure, composed of NIPA-rich and SA-rich domains. In addition, the SANS experiments reveal the mesoscopic structural features during the dehydration process. As the concentration of the network polymers increases, NIPA-rich and water-rich domains segregate in the gel. Then, an electrostatic interaction between the segregated domains induces a microphase-separated structure in the limit of the dehydrated NIPA−SA gel.

Added Salt Effect on the Intermolecular Correlation in Flexible Polyelectrolyte Solutions: Small-Angle Scattering Study

The intermolecular correlation due to electrostatic repulsion in flexible polyelectrolyte solutions as a function of ionic strength has been studied using small-angle neutron and X-ray scattering (SAXS and SANS) techniques. The ionic strength was changed by adding low molecular weight salts at a fixed polyion concentration (C = 0.25 mol/L). To solve the controversy about the added salt effect on the characteristic maximum in small-angle scattering of polyelectrolyte solutions, separation of the total scattering function into the intra- and intermolecular parts has been performed. With increasing the ionic strength of the solution the maximum position qm in the total scattering function of SAXS and SANS slightly shifts toward the lower scattering vector and subsequently disappears, whereas the maximum position in the intermolecular scattering function slightly shifts to the higher scattering vector, but the peak itself does not disappear even for the highest ionic strength of the present study though it becomes weaker. The intramolecular scattering function is enhanced in the lower scattering vector (q < ) when the ionic strength increases. Thus, it turned out that the apparent shift of the maximum in the total scattering function is caused by the combination of the intra- and intermolecular scattering functions.

Small-Angle Scattering Study of TAC8: A Surfactant with Cation Complexing Potential

TAC8 is a new surfactant molecule. Two octyl chains form the hydrophobic part of the molecule whereas the hydrophilic part is made of two glucose groups and a cyclam ring, which gives the molecule a potential for complexing metal ions or compounds. Aqueous solutions of pure TAC8 and of TAC8 with equimolar complexed CuF2 are studied using small-angle neutron and X-ray scattering. The shape and dimensions of the micelles are determined from the scattering data using two different approaches. The first approach is model independent and uses indirect Fourier transformation of the scattering data followed by square-root deconvolution of the obtained pair-distance distribution function in order to determine the scattering length density profile. In the second approach a molecular constrained model of the micelles is fitted to the X-ray and neutron scattering data simultaneously. The results of these two different approaches agree very well. The analysis shows that both the pure TAC8 and the TAC8 with complexed CuF2 aggregate into short cylindrical micelles with aggregation numbers of approximately 20. The micelles of TAC8 with CuF2 are quite monodisperse in the concentration range studied, and their effective charge is very low compared to that of typical ionic micelles.

Neutron and X-Ray Small Angle Scattering Studies of Rapidly Quenched La-Fe Alloys

Small angle scattering of neutrons and x-rays were measured in a range of 0.008 ≤ q [ =(4π/λ)sin θ] ≤0.2 A -1 for rapidly quenched La-Fe alloys. As-quenched alloys are superparamagnetic at room temperature and ferromagnetic below about 270 K. Both neutron and x-ray scattering show decreases of the intensity proportional to q -3 for the as-quenched specimen. Little effect was observed on decreasing the temperature to 10 K or with the application of an external magnetic field up to 5 kOe. These facts indicate that the scattering is not of magnetic origin. After an annealing at 350° C for 30 min., the alloys change into antiferromagnets. After heat treatment, the scattering intensity decreased considerably and its q -dependence changed to q -4 . These results are discussed based on a two-stage solidification process of the alloy, estimated from magnetic measurements, and the “density variation between random boundaries” model caused by nonmagnetic Fe atoms dissolved at the periphery of La grains.

An Ultra Small Angle Scattering Study of Hydrogen in Metals

A diffractometer using perfect crystals in symmetric Bragg arrangement, hence being useful for both neutron and X-ray radiation, has been built. The angular resolution of that instrument is better than 1 microradian, which corresponds to a scattering vector resolution of about 10-6 Å-1. This spectrometer was equipped with a laser light adjustment system which is sensitive to the relative angular position of the two perfect crystals. The spectrometer was used for the mea­surement of neutron scattering at very low angles of hydrated niobium and vanadium samples. The experimental results show an anomalously low attenuation of the neutrons when the metal-H sample is within the solubility a region. This property is explained by a lattice gas model of atomic H in the α-phase of the system. In the two phase region (α - β) a stronger attenuation of the neutron beam occurs due to the sample now being in an ordered interstitial solution phase.

Neutron Small-Angle Scattering Study of the Decomposition of an Fe–Cr Alloy in the Unstable State

The decomposition kinetics of an Fe–Cr alloy which lies in the unstable region has been studied by neutron small-angle scattering. The time evolution of scattered intensity is not consistent with Cahn's classical theory of spinodal decomposition, but with the recent theories and the Monte Carlo simulations of the phase separation of alloys.

General shape and hapten-induced conformational changes of pig antibody against dinitrophenyl. A small-angle scattering study.

Pig antibodies against dinitrophenyl were studied by neutron small-angle scattering and X-ray small-angle scattering with particular attention to the analysis of cross-section plots and determination of the radii of gyration of cross-section. The experimentally determined molecular parameters Rg (radius of gyration), Rq1 and Rq2 (two different radii of gyration of cross-section characterizing every antibody sample) show that the shapes of the two antibody types, precipitating and non-precipitating, are similar. The non-precipitating antibody is slightly more compact. The parameters Rg, Rq1 and Rq2 of complexes of antibodies with the hapten, 8-dinitrophenyl-5,8-aza-4-oxo-octanoic acid, are smaller than those of the free antibody. This indicates that a conformational change is induced by the binding of the hapten. The character of the change of parameters is consistent with a view that the observed contraction of the molecule proceeds via similarity transformation. In order to design a model of a pig antibody molecule, isolated building blocks of the molecule, the Fab and Fc fragments, were first studied. A comparison of the scattering curves with various models of fragments showed, however, that the isolated fragments acquire in solution elongated rod-like shapes. Over 300 tentative models of the intact antibody molecule, built of small identical spheres, were constructed before a good fit with the experimental data was achieved. The most probable models have a cavity in the Fc part and the Fab parts are either fully extended or slightly bent downwards to the Fc part.

X‐Ray and Neutron Small‐Angle Scattering Studies of the Complex between Protein S1 and the 30‐S Ribosomal Subunit

X-ray neutron solution scattering experiments have been done to investigate the influence of the binding of ribosomal protein S1 on the conformation of the 30-S ribosomal subunit of Escherichia coli. The following conclusions were made. 1. The alterations (if any) in conformation of the non-S1 parts of the 30-S subunit induced by S1 binding are too small to be detected (less than 0.1 nm change in radius of gyration). 2. The center of gravity of protein S1 bound to the 30-S subunit is quite far from the center of gravity of the particle (approximately 7.5 nm).

X線小角散乱法によるCu-4%Ti合金の低温時効初期過程の研究

X線小角散乱法によるCu-4%Ti合金の低温時効初期過程の研究

X線小角散乱法によるCu-4% Ti合金の初期時効に続く時効過程の研究

X線小角散乱法によるCu-4% Ti合金の初期時効に続く時効過程の研究