Photon Correlation Spectroscopy Measurements Research Articles

Particle Dynamics in a Diblock-Copolymer-Based Dodecagonal Quasicrystal and Its Periodic Approximant by X-Ray Photon Correlation Spectroscopy.

Temperature-dependent x-ray photon correlation spectroscopy (XPCS) measurements are reported for a binary diblock-copolymer blend that self-assembles into an aperiodic dodecagonal quasicrystal and a periodic Frank-Kasper σ phase approximant. The measured structural relaxation times are Bragg scattering wavevector independent and are 5 times faster in the dodecagonal quasicrystal than the σ phase, with minimal temperature dependence. The underlying dynamical relaxations are ascribed to differences in particle motion at the grain boundaries within each of these tetrahedrally close-packed assemblies. These results identify unprecedented particle dynamics measurements of tetrahedrally coordinated micellar block polymers, thus expanding the application of XPCS to ordered soft materials.

Orientational ordering and assembly of silica-nickel Janus particles in a magnetic field.

The orientation ordering and assembly behavior of silica-nickel Janus particles in a static external magnetic field were probed by ultra small-angle X-ray scattering (USAXS). Even in a weak applied field, the net magnetic moments of the individual particles aligned in the direction of the field, as indicated by the anisotropy in the recorded USAXS patterns. X-ray photon correlation spectroscopy (XPCS) measurements on these suspensions revealed that the corresponding particle dynamics are primarily Brownian diffusion [Zinn, Sharpnack & Narayanan (2023). Soft Matter, 19, 2311-2318]. At higher fields, the magnetic forces led to chain-like configurations of particles, as indicated by an additional feature in the USAXS pattern. A theoretical framework is provided for the quantitative interpretation of the observed anisotropic scattering diagrams and the corresponding degree of orientation. No anisotropy was detected when the magnetic field was applied along the beam direction, which is also replicated by the model. The method presented here could be useful for the interpretation of oriented scattering patterns from a wide variety of particulate systems. The combination of USAXS and XPCS is a powerful approach for investigating asymmetric colloidal particles in external fields.

Nanoparticle Diffusion in Miscible Polymer Nanocomposite Melts

X-ray photon correlation spectroscopy measurements were used to quantify the dynamics of bare and bimodal grafted silica nanoparticles mixed with PEO melts of different molecular weights. In dilute polymer nanocomposite (PNC) samples, we find diffusive NP behavior as described by the Stokes–Einstein relationship so long as the adsorbed PEO polymer layer is taken into account in determining both the effective NP size and its role on composite viscosity. The size of this bound layer was found to be approximately 2Rg, where Rg is the chain radius of gyration. We also expanded our system to investigate how the dynamics of grafted NPs differ from bare NPs with an adsorbed layer. We showed that the dynamics again can be determined by an effective NP radius at a scale smaller than the effective interparticle spacing; however, at larger length scales, the morphology and grafting parameters play a major role in the system dynamics. These results allow us to quantify NP ordering driven by polymer crystallization. It has previously been speculated that behavior is controlled by the relative ratio of time scale of crystal growth and the diffusive time scale of the NPs, a Peclet number. When the former time scale is longer, then the NPs are expected to be segregated into the interlamellar amorphous zones, while the NPs are too slow to be reorganized in the opposite case. We show here that this conjecture is quantitatively correct and the demarcation in behavior occurs for Pe = 1. Thus, we provide a way to estimate a critical spherulite growth rate for any semicrystalline PNC, at which a given NP can be ordered. Together, the results of this study permit us to tunably design PNCs through directed dispersion of NPs in a polymer matrix.

Effects of the Grazing Incidence Geometry on X-ray Photon Correlation Spectroscopy Measurements.

X-ray photon correlation spectroscopy (XPCS) is a versatile tool to measure dynamics on the nanometer to micrometer scale in bulk samples. XPCS has also been applied in grazing incidence (GI) geometry to examine the dynamics of surface layers. However, considering GI scattering experiments more universally, the GI geometry leads to a superposition of signals due to reflection and refraction effects, also known from the distorted-wave Born approximation (DWBA). In this paper, the impact of these reflection and refraction effects on the correlation analysis is determined experimentally by measuring grazing incidence transmission XPCS (GT-XPCS) and grazing incidence XPCS (GI-XPCS) simultaneously for a thin film sample, showing non-equilibrium dynamics. The results of the GI and GT geometry comparisons are combined within the framework of the standardly applied, simplified DWBA. These calculations allow identifying the main contributions of the detected signal from the leading scattering terms along the out-of-plane direction qz, which dominate the measured intensity pattern on the detector. In combination with the calculation of the non-linear effect of refraction in GTSAXS and GISAXS, it is possible to identify experimental conditions that can be chosen to run experiments and data analysis as close as possible to transmission XPCS and to explain which limitations for data interpretations are observed. Consequently, the beam exposure can be significantly reduced by using GI geometry only. Calculations of experimental settings prior to experiments are detailed to determine suitable qz regions for a variety of material systems measured in bulk-sensitive GI-XPCS experiments, allowing us to determine the scaling behavior of typical decay times as a function of q that is comparable to the scaling behavior obtained in distortion-free GT-XPCS or transmission XPCS experiments.

In situ observation of the structure and dynamics of a polymer solution through nonsolvent-induced phase separation by x-ray photon correlation spectroscopy

Nonsolvent-induced phase separation (NIPS) is a complex but important phenomenon involved in the manufacture of fibers and other polymeric industrial products. We performed in situ x-ray photon correlation spectroscopy (XPCS) measurements on a cuprammonium cellulose solution immersed in aqueous acetone solution to reveal the structure and dynamics involved in the NIPS process on the microscopic scale. A combination of the structural information from the small angle x-ray scattering profiles and the dynamic information from the XPCS analysis revealed that NIPS occurs via two steps: dilution of the polymer solution by the solvent and desorption of the solvent from the polymer solution. This study will provide an opportunity for the fundamental understanding of NIPS, which is important from both the scientific and industrial viewpoints.

Microscopic Origins of the Nonlinear Behavior of Particle-Filled Rubber Probed with Dynamic Strain XPCS.

The underlying microscopic response of filler networks in reinforced rubber to dynamic strain is not well understood due to the experimental difficulty of directly measuring filler network behavior in samples undergoing dynamic strain. This difficulty can be overcome with in situ X-ray photon correlation spectroscopy (XPCS) measurements. The contrast between the silica filler and the rubber matrix for X-ray scattering allows us to isolate the filler network behavior from the overall response of the rubber. This in situ XPCS technique probes the microscopic breakdown and reforming of the filler network structure, which are responsible for the nonlinear dependence of modulus on strain, known in the rubber science community as the Payne effect. These microscopic changes in the filler network structure have consequences for the macroscopic material performance, especially for the fuel efficiency of tire tread compounds. Here, we elucidate the behavior with in situ dynamic strain XPCS experiments on industrially relevant, vulcanized rubbers filled (13 vol %) with novel air-milled silica of ultrahigh-surface area (UHSA) (250 m2/g). The addition of a silane coupling agent to rubber containing this silica causes an unexpected and counterintuitive increase in the Payne effect and decrease in energy dissipation. For this rubber, we observe a nearly two-fold enhancement of the storage modulus and virtually equivalent loss tangent compared to a rubber containing a coupling agent and conventional silica. Interpretation of our in situ XPCS results simultaneously with interpretation of traditional dynamic mechanical analysis (DMA) strain sweep experiments reveals that the debonding or yielding of bridged bound rubber layers is key to understanding the behavior of rubber formulations containing the silane coupling agent and high-surface area silica. These results demonstrate that the combination of XPCS and DMA is a powerful method for unraveling the microscale filler response to strain which dictates the dynamic mechanical properties of reinforced soft matter composites. With this combination of techniques, we have elucidated the great promise of UHSA silica when used in concert with a silane coupling agent in filled rubber. Such composites simultaneously exhibit large moduli and low hysteresis under dynamic strain.

In situ high-pressure wide-angle hard x-ray photon correlation spectroscopy: A versatile tool probing atomic dynamics of extreme condition matter

With the advent of new synchrotron radiation x-ray sources that provide a significantly enhanced coherent flux, high-energy x-ray photon correlation spectroscopy measurements can be performed on materials in a diamond anvil cell. Essential information on atomic dynamics that was previously inaccessible can be obtained for various novel phenomena emerging under extreme conditions. This article discusses the importance, feasibility, and experimental details of this technique, as well as the opportunities that it offers to address critical scientific challenges.

Spatial-Temporal Dynamics at the Interface of 3D-Printed Photocurable Thermoset Resin Layers

Additive manufacturing (AM) is used to fabricate polymeric materials into complex three-dimensional (3D) structures. As the 3D structure is built by sequential layer-by-layer deposition of filaments dispensed from a translating nozzle (in the case of extrusion-based printing), defects often form at the filament-filament interface. The out-of-equilibrium structural development that occurs during the printing process is difficult to directly measure by quantitative means, limiting our understanding of the physical mechanisms at play. Here, we utilize in operando X-ray photon correlation spectroscopy (XPCS) measurements with microbeam capability to probe the real-time structural evolution at the filament-filament interface during extrusion 3D printing. We investigate the solidification of a dual-cure (UV/thermal) acrylate/epoxy resin during multilayer 3D printing as a rational model by tracking the nanoscale motion of filler particles embedded in the resin. The spatially and temporally resolved dynamics (on length scales from several nm to a few hundreds of nm and time scales of 10–3 < t < 103 seconds) are measured during the deposition of a single filament as well as during the deposition of a second layer on top of the cured underlayer. The addition of a second layer introduces structural perturbations at the interface and results in accelerated interfacial dynamics compared to those of the cured underlayer. However, as time proceeds, the local dynamical heterogeneity disappears, and the evolution of the dynamics progresses uniformly within the entire interfacial region. The homogeneity across the interface results from the formation of an interpenetrated epoxy network that spans across the first and second filaments. This homogeneous interface is responsible for the isotropic tensile properties of a 3D-printed sample that are independent of print direction and nearly the same as the bulk (non-3D-printed) sample. The XPCS microrheology approach provides insight into the dynamics-process-property relationship at the printed filament interfaces.

Resolving Salt-Induced Agglomeration of Laponite Suspensions Using X-ray Photon Correlation Spectroscopy and Molecular Dynamics Simulations.

Linking the physics of the relaxation behavior of viscoelastic fluids as they form arrested gel states to the underlying chemical changes is essential for developing predictive controls on the properties of the suspensions. In this study, 3 wt.% laponite suspensions are studied as model systems to probe the influence of salt-induced relaxation behavior arising from the assembly of laponite nanodisks. X-ray Photon Correlation Spectroscopy (XPCS) measurements show that laponite suspensions prepared in the presence of 5 mM concentrations of CaCl2, MgCl2 and CsCl salts accelerate the formation of arrested gel states, with CaCl2 having a significant impact followed by CsCl and MgCl2 salts. The competing effects of ion size and charge on relaxation behavior are noted. For example, the relaxation times of laponite suspensions in the presence of Mg2+ ions are slower compared to Cs+ ions despite the higher charge, suggesting that cation size dominates in this scenario. The faster relaxation behavior of laponite suspensions in the presence of Ca2+ ions compared to Cs+ ions shows that a higher charge dominates the size of the ion. The trends in relaxation behavior are consistent with the cluster formation behavior of laponite suspensions and the electrostatic interactions predicted from MD simulations. Charge balance is achieved by the intercalation of the cations at the negatively charged surfaces of laponite suspensions. These studies show that the arrested gel state of laponite suspensions is accelerated in the presence of salts, with ion sizes and charges having a competing effect on relaxation behavior.

Performance of the time-resolved ultra-small-angle X-ray scattering beamline with the Extremely Brilliant Source.

The new technical features and enhanced performance of the ID02 beamline with the Extremely Brilliant Source (EBS) at the ESRF are described. The beamline enables static and kinetic investigations of a broad range of systems from ångström to micrometre size scales and down to the sub-millisecond time range by combining different small-angle X-ray scattering techniques in a single instrument. In addition, a nearly coherent beam obtained in the high-resolution mode allows multispeckle X-ray photon correlation spectroscopy measurements down to the microsecond range over the ultra-small- and small-angle regions. While the scattering vector (of magnitude q) range covered is the same as before, 0.001 ≤ q ≤ 50 nm-1 for an X-ray wavelength of 1 Å, the EBS permits relaxation of the collimation conditions, thereby obtaining a higher flux throughput and lower background. In particular, a coherent photon flux in excess of 1012 photons s-1 can be routinely obtained, allowing dynamic studies of relatively dilute samples. The enhanced beam properties are complemented by advanced pixel-array detectors and high-throughput data reduction pipelines. All these developments together open new opportunities for structural, dynamic and kinetic investigations of out-of-equilibrium soft matter and biophysical systems.

Shea butter (Vitellaria paradoxa) and Pentaclethra macrophylla oil as lipids in the formulation of Nanostructured lipid carriers

Natural lipids obtained from plant or animal sources have become very useful in drug delivery due to their better biocompatibility and lower in vivo toxicity compared to synthetic and semi-synthetic lipids. Pentaclethra macrophylla oil and shea butter (Vitellaria paradoxa) have been evaluated as lipids in the formulation of nanostructured lipid carriers (NLCs) using four surfactants (Tween 80, Span 20, sodium dodecyl sulfate and Plantacare® 2000). Nanostructured lipid carriers were prepared by high-pressure homogenization and characterized using photon correlation spectroscopy (PCS), laser diffraction (LD), and zeta potential measurements. The optimal formulations were loaded with Cola hispida extract and the physical properties and in vitro antioxidant activities were evaluated. Stable nanosized lipid carriers were obtained using Tween 80 and Span 20 at the ratio of 1:1 as emulsifying agents. Formulations containing 2% w/w shea butter and 8%w/wP. macrophylla oil had the lowest particle sizes (131.467 ± 1.504 to 163.330 ± 1.909) and polydispersity index (0.143 ± 0.005 to 0.197 ± 0.018). The extract-loaded formulations were stable and demonstrated significant (p < 0.05) antioxidant capacity except for formulations prepared with carnauba wax which demonstrated significantly (p < 0.01) lower antioxidant capacity compared to the extract and the other formulations. The properties of the NLCs were influenced by the type and concentration of solid lipid used. Pentaclethra macrophylla oil and shea butter were valuable lipids in the formulation of nanostructured lipid carriers for the delivery of Cola hispida extract.

Viscosity reduction in polymer nanocomposites: Insights from dynamic neutron and X‐ray scattering

AbstractThe addition of nanoparticles to a polymer matrix can in certain cases induce a reduction in viscosity, with respect to the pure matrix, in the resulting composites. This counterintuitive phenomenon cannot be explained using the most common rheological models. For this reason, it has been chosen as a good example in this paper to demonstrate the value and methods of dynamic X‐ray and neutron scattering techniques for the investigation of polymer nanocomposites. An overview of the main results on this topic is presented together with an introduction to the basic concepts relating to X‐ray photon correlation spectroscopy, neutron backscattering, and neutron spin echo measurements.

Anomalous fast atomic dynamics in bulk metallic glasses

It is commonly believed that the strong glass formers tend to be dense packing and have rather slow atomic dynamics. Here, we report that the anomalous fast atomic dynamics exist in an Au55Cu20Ag5Si20 metallic glass (MG) with good glass forming ability (GFA) by combining X-ray photon correlation spectroscopy measurements with ab initio molecular dynamics simulations. The fast dynamics are mainly originated from the increased mobility of Cu atoms by Ag addition. Ag atoms are inclined to locate at Cu-centered <0, 2, 8, 1> motifs, which slow or accelerate the dynamics of shell Cu atoms, depending on whether Ag atoms appear at the first shells or not, leading to the formation of structural heterogeneity at the atomic level. The results enrich the understanding of atomic dynamics in Cu–Ag-containing MGs and will trigger more studies on the dynamics-GFA relationship in MGs.

Water‐in‐Fluorocarbon Nanoemulsions Stabilized by Phospholipids and Characterized for Pharmaceutical Applications

AbstractFluorocarbons are one of the most promising hydrophobic phases for future pharmaceutical production processes and various biomedical applications. Yet, because of their specific characteristics such as high density and refractive index similar to water, analysis of water‐in‐fluorocarbon (w/fc) nanoemulsions remains a challenge. The present work examines w/fc nanoemulsions stabilized with phospholipids as natural emulsifiers and tackles the measuring problems of photon correlation spectroscopy (PCS) when used for investigation of fluorocarbon nanoemulsions. These emulsions are suitable to form liposomes via centrifugation and thus, are required to meet certain criteria such as stability and size. The results imply a stability of up to 4 weeks with an average size of 180 nm. The intensity mean diameter gained from PCS measurements shows large scattering directly after sonication which is due to gas bubbles from sonication. The number mean is not influenced by gas bubbles and gives a more accurate depiction of the produced nanoemulsions. These findings are supported by small‐angle X‐ray scattering data, which are additionally applied for liposome analysis measuring a size of approximately 60 nm.

A microvolume shear cell for combined rheology and x-ray scattering experiments.

An experimental setup is presented for x-ray scattering studies of soft matter under shear flow that employs a low-background coaxial capillary cell coupled to a high-resolution commercial rheometer. The rotor of the Searle type cell is attached to the rheometer shaft, which allows the application of either steady or oscillatory shear of controlled stress or rate on the sample confined in the annular space between the stator and the rotor. The shearing device facilitates ultrasmall-angle x-ray scattering and ultrasmall-angle x-ray photon correlation spectroscopy measurements with relatively low scattering backgrounds. This enables the elucidation of weak structural features otherwise submerged in the background and probes the underlying dynamics. The performance of the setup is demonstrated by means of a variety of colloidal systems subjected to different rheological protocols. Examples include shear deformation of a short-range attractive colloidal gel, dynamics of dilute colloids in shear flow, distortion of the structure factor of a dense repulsive colloidal suspension, shear induced ordering of colloidal crystals, and alignment of multilamellar microtubes formed by a surfactant-polysaccharide mixture. Finally, the new possibilities offered by this setup for investigating soft matter subjected to shear flow by x-ray scattering are discussed.

Dynamics at the crystal-melt interface in a supercooled chalcogenide liquid near the glass transition

Direct quantitative measurements of nanoscale dynamical processes associated with structural relaxation and crystallization near the glass transition are a major experimental challenge. These type of processes have been primarily treated as macroscopic phenomena within the framework of phenomenological models and bulk experiments. Here, we report x-ray photon correlation spectroscopy measurements of dynamics at the crystal-melt interface during the radiation induced formation of Se nano-crystallites in pure Se and in binary AsSe4 glass-forming liquids near their glass transition temperature. We observe a heterogeneous dynamical behaviour where the intensity correlation functions g2(q, t) exhibits either a compressed or a stretched exponential decay, depending on the size of the Se nano-crystallites. The corresponding relaxation timescale for the AsSe4 liquid increases as the temperature is raised, which can be attributed to changes in the chemical composition of the melt at the crystal-melt interface with the growth of the Se nano-crystallites.

Design of an amplitude-splitting hard x-ray delay line with subnanoradian stability.

We present the design and analysis of a hard x-ray split-delay optical arrangement that combines diffractive and crystal optics. Transmission gratings are employed to achieve the much-desired amplitude splitting and recombination of the beam. Asymmetric channel-cut crystals are utilized to tune the relative delay time. The use of a dispersion-compensation arrangement of the crystals allows the system to achieve subnanoradian pointing stability during a delay scan. It also minimizes wavefront distortion and preserves the pulse front and pulse duration. We analyze the performance of a prototype design that can cover a delay time range of 15 ps with a sub-20 fs time resolution at 10 keV. We anticipate that this system can fully satisfy the very demanding stability requirements for performing split-pulse x-ray photon correlation spectroscopy measurements for the investigation of fast atomic scale dynamics in complex disordered matter.

Bovine Heparin Demonstrates the Same Interaction with HIT Antibodies As Porcine Heparin

Heparin, an anticoagulant widely used in numerous medical applications, is considered an essential medicine by the WHO. Due to its high volume use and that it is the parent material for low molecular weight heparins, there is potential for the raw material to be in short supply. The African swine fever epidemic in China, ongoing since August 2018, has added further restraints on heparin source material supply. At present medical grade heparin in the US is only derived from porcine intestinal mucosa; however, there are explorations into using bovine, ovine, and other sources. Bovine heparin, once common place in the US pharmaceutical sector, is again under consideration by the US FDA. This study focused on the primary immunogenic activity associated with heparin, that is heparin-induced thrombocytopenia (HIT), and how the interaction of bovine heparin with functional HIT antibodies compares to that of porcine heparin. Materials and Methods Bovine unfractionated heparin from multiple manufacturers was compared to commercial medical grade porcine heparin obtained from US pharmacies. The US Pharmacopeia porcine heparin standard was used to determine potency equivalence. Antibodies to the complex of platelet factor 4/heparin (PF4/heparin) from banked clinically confirmed HIT patient apheresis fluids were combined with heparin and donor platelet rich plasma (PRP; blood collected in citrate from volunteers after signing a consent document). Heparins were tested at final concentrations of 0.1, 0.4, 0.8, 1, and 100 U/mL. The platelet activation response was determined on the BioData PAP-8 Platelet Aggregometer and quantitated in terms of primary slope (PS), area under the curve (AUC), maximum aggregation (MA), and final aggregation (FA). Characterization of the biophysical interaction between varying molar ratios of human PF4 and heparin was performed using photon correlation spectroscopy (PCS) and zeta potential (Zp) measurements of PF4/heparin complexes using Zetasizer Nano ZS instrumentation and software. Differences between bovine and porcine heparin were assessed by t-test or Mann-Whitney test. Concentration-response curves were analyzed by two-way ANOVA followed by the Holm-Sidak multiple comparison test using SigmaPlot software. Results Platelet activation to PF4/heparin antibodies at bovine and porcine heparin concentrations of 0.1 U/mL (56 ± 9 % vs. 54 ± 11 % MA) and 0.4 U/mL (59 ± 10 % vs. 65 ± 8 % MA) were the same with the expected inhibition (9 ± 4% MA) at the supra-therapeutic concentration of 100 U/mL. Consistent responses were obtained across 21 lots of bovine heparin, 30 lots of porcine heparin, and 38 platelet-HIT antibody combinations. The HIT potential of bovine heparin and porcine heparin was not statistically different (p&gt;0.05). At higher medical use doses, the platelet aggregation response in the presence of HIT antibodies was actually lower for bovine heparin than porcine heparin (0.8 U/mL, 49 ± 10 % vs. 64 ± 9 % MA, p&lt;0.05; and 1.0 U/mL, 45 ± 11 % vs. 62 ± 9 % MA, p&lt;0.05). By PCS, it was observed that the maximal aggregation between PF4 and either porcine or bovine heparin occurred at comparable molar ratios (7.3 ± 1.5 vs. 6.4 ± 0). Although the porcine and bovine heparins exhibited comparable molecular weights (16,333 ± 153 vs. 16,790 ± 230 Da) and polydispersities (1.19 ± 0.02 vs. 1.15 ± 0.01), porcine heparin formed somewhat larger complexes with PF4 (1113 ± 65 nm) than did bovine heparin (863 ± 68 nm). The molar ratios of PF4 to heparin at which the charge of the complex was fully neutralized (Zp = 0) was comparable for porcine and bovine heparin (9.04 ± 0.19 vs. 9.97 ± 0.65). Consistent responses were obtained across 4 lots of bovine heparin and 3 lots of porcine heparin. Conclusions Bovine heparin and porcine heparin had the same in vitro functional platelet activation response in the presence of HIT antibodies, the same potential to form complexes with human PF4, and the same associated features that make PF4 immunogenic. This investigation demonstrates that bovine heparins should have a similar immunogenic response as porcine heparin at equi-unit dosing. Current refinements in the manufacturing process for bovine and porcine heparins have led to well-characterized and purified products which is reflected in their comparable biological behavior. Disclosures No relevant conflicts of interest to declare.

Distinguishing Between Monomeric scFv and Diabody in Solution Using Light and Small Angle X-ray Scattering.

Depending on the linker length between the V and the V domain, single-chain Fv (scFv) antibody fragments form monomers, dimers (diabodies) or higher oligomers. We aimed at generating a diabody of the anti-MET antibody 3H3 to use it as crystallization chaperone to promote crystallization of the MET ectodomain through the introduction of a pre-formed twofold axis of symmetry. Size exclusion chromatography, however, suggested the protein to be monomeric. Hence, we used scattering techniques applied to solutions to further investigate its oligomerization state. The small angle X-ray scattering (SAXS) curve measured for our protein nicely fits to the scattering curve calculated from the known crystal structure of a diabody. In addition, concentration-dependent photon correlation spectroscopy (PCS) measurements revealed a hydrodynamic radius of 3.4 nm at infinite dilution and a negative interaction parameter , indicating attractive interactions that are beneficial for crystallization. Both SAXS and PCS measurements clearly suggest our antibody fragment to be a diabody in solution. Chemical cross-linking with glutaraldehyde and cell motility assays confirmed this conclusion.

A new framework for X-ray photon correlation spectroscopy analysis from polycrystalline materials.

We report a new analytical framework for interpreting data from X-ray photon correlation spectroscopy measurements on polycrystalline materials characterized by strong scattering intensity variations at fixed wavevector magnitude (i.e., anisotropic scattering). Currently, no analytical method exists for the interpretation of the time-dependent anisotropic scattering from such materials. The framework is applied to interrogate the dynamics of a spherical micelle-forming diblock copolymer melt below the order-disorder transition, wherein finite size grains of a micellar body-centered cubic structure produce anisotropic scattering. A wealth of analytical information is recovered from a simple measurement, including distributions of relaxation times and speeds associated with micelles within grains. The findings of this study demonstrate the efficacy of this new analytical method, which may be readily adapted for application to a variety of materials and systems.