Difference in structural changes of surfactant aggregates near solid surface under shear flow versus those in the bulk.

In water, the nonionic surfactant pentaethylene glycol monododecyl ether (C12E5) forms multi-lamellar vesicles upon application of shear, attributed to buckling instability of the surfactant layers. In the standard setup for applying shear, a pair of solid substrates is moved in opposite directions, and a non-slip condition at the solid surface is assumed. Based on theoretical predictions, the effective viscosity of the fluid surrounding the membrane is modified in this process, and this confinement may affect membrane fluctuation.

Effects of Fe Ions, Ultraviolet Irradiation, and Heating on Microscopic Structures of Black Lacquer Films.

The chemical reaction between Fe and lacquer has been used to create the black color in lacquer coatings since ancient times. Here, the effects of Fe ion addition, UV irradiation, and heating on the microscopic structures of black lacquer films were investigated by using X-ray absorption near edge structure (XANES), extended X-ray absorption fine structure (EXAFS), Fourier transform-infrared spectroscopy (FT-IR), small-angle X-ray scattering (SAXS), and small angle neutron scattering (SANS). The EXAFS result indicated that heating and UV irradiation made the coordination structure of Fe in the lacquer nonuniform, and that heating caused the greatest nonuniformity.

Equation Elucidating the Catalyst-Layer Proton Conductivity in a Polymer Electrolyte Fuel Cell Based on the Ionomer Distribution Determined Using Small-Angle Neutron Scattering.

The performance of a polymer electrolyte fuel cell can be enhanced by improving the proton conductivity of the catalyst layer, where the oxygen reduction reaction generates electrochemical power. Protons are conducted through the ionomer coatings on catalyst-supporting carbon particles, which form porous structures that facilitate oxygen diffusion during the reaction within the catalyst layer. Therefore, while a higher ionomer content in the catalyst layer is favorable, the proton conductivity is additionally governed by the type of carbon support.

Extended -range small-angle neutron scattering to understand the morphology of proton-exchange membranes: the case of the functionalized syndiotactic-polystyrene model system.

Semi-crystalline polymers exhibit microphase separation into crystalline and amorphous domains characterized by multiple structural levels with sizes ranging from ångströms to hundreds of nanometres. The combination of small-angle (SANS) and wide-angle (WANS) neutron scattering on the same beamline enables reliable characterization of such materials under application-relevant conditions, with the unique advantage of contrast variation by controlled labelling, allowing the structure of such multi-component systems to be resolved in detail. This paper reports a structural analysis performed on deuterated polymer membranes based on syndiotactic polystyrene (sPS) using an extended -range SANS and WANS combination, always with the same neutron scattering instrument, either a pinhole SANS diffractometer installed at a research reactor or a 'small- and wide-angle' time-of-flight diffractometer installed at a neutron spallation source.

Direct observation of concentration fluctuations in Au-Si eutectic liquid by small-angle neutron scattering.

It is well-known that eutectic gold-silicon (Au-Si) alloys exhibit anomalous melting point depression, which is more than 1000 °C from the melting point of elemental Si (1414 °C). The melting point depression in eutectic alloys is generally explained in terms of a decrease of the free energy by mixing. However, it is difficult to understand the anomalous melting point depression only from the stability of the homogeneous mixing.

On the Proton Conduction Pathways in Polyelectrolyte Membranes Based on Syndiotactic-Polystyrene.

When functionalized by the solid-state sulfonation process, the amorphous regions of the semi-crystalline syndiotactic-polystyrene (sPS) become hydrophilic, and thus can conduct protons upon membrane hydration, which increases the interest in this material as a potential candidate for applications with proton exchange membranes. The resistance of sulfonated sPS to oxidative decomposition can be improved by doping the membrane with fullerenes. In previous work, we have described the morphology in hydrated sulfonated sPS films doped with fullerenes on different length scales as determined by small-angle neutron scattering (SANS) and the structural changes in such membranes as a function of the degree of hydration and temperature.

Star-Polymer-DNA Gels Showing Highly Predictable and Tunable Mechanical Responses.

Dynamically crosslinked gels are appealing materials for applications that require time-dependent mechanical responses. DNA duplexes are ideal crosslinkers for building such gels because of their excellent sequence addressability and flexible tunability in bond energy. However, the mechanical responses of most DNA gels are complicated and unpredictable.

Structural changes in pH-responsive gelatin/hydroxypropyl methylcellulose phthalate blends aimed at drug-release systems.

The present study aimed to investigate the thermal- and pH-dependent gelation behavior of gelatin/HPMCP blends using ultraviolet (UV) spectrophotometry, viscoelasticity, and dynamic light scattering (DLS). We found that the release of lisinopril from gelatin/HPMCP gels can be inhibited at low pH. UV spectrophotometric analysis showed that pH had a significant effect on the transparency of aqueous HPMCP systems and gelatin/HPMCP gels.

Distinguishing Adsorbed and Deposited Ionomers in the Catalyst Layer of Polymer Electrolyte Fuel Cells Using Contrast-Variation Small-Angle Neutron Scattering.

The ionomers distributed on carbon particles in the catalyst layer of polymer electrolyte fuel cells (PEFCs) govern electrical power via proton transport and oxygen permeation to active platinum. Thus, ionomer distribution is a key to PEFC performance. This distribution is characterized by ionomer adsorption and deposition onto carbon during the catalyst-ink coating process; however, the adsorbed and deposited ionomers cannot easily be distinguished in the catalyst layer.

Probing the adsorption of nonionic micelles on different-sized nanoparticles by scattering techniques.

The interaction of nanoparticles with surfactants is extensively used in a wide range of applications from enhancing colloidal stability to phase separation processes as well as in the synthesis of noble functional materials. The interaction is highly specific depending on the charged nature of the surfactant. In the case of nonionic surfactants, the micelles adsorb on the surface of nanoparticles.

NACore Amyloid Formation in the Presence of Phospholipids.

Amyloids are implicated in many diseases, and disruption of lipid membrane structures is considered as one possible mechanism of pathology. In this paper we investigate interactions between an aggregating peptide and phospholipid membranes, focusing on the nanometer-scale structures of the aggregates formed, as well as on the effect on the aggregation process. As a model system, we use the small amyloid-forming peptide named NACore, which is a fragment of the central region of the protein α-synuclein that is associated with Parkinson's disease.

The Multilevel Structure of Sulfonated Syndiotactic-Polystyrene Model Polyelectrolyte Membranes Resolved by Extended Q-Range Contrast Variation SANS.

Membranes based on sulfonated synditoactic polystyrene (s-sPS) were thoroughly characterized by contrast variation small-angle neutron scattering (SANS) over a wide Q-range in dry and hydrated states. Following special sulfonation and treatment procedures, s-sPS is an attractive material for fuel cells and energy storage applications. The film samples were prepared by solid-state sulfonation, resulting in uniform sulfonation of only the amorphous phase while preserving the crystallinity of the membrane.

A new simultaneous measurement system of wide Q-range small angle neutron scattering combined with polarized Fourier transform infrared spectroscopy.

Small angle neutron scattering (SANS) is a versatile and convenient method to investigate the higher order structure of molecular assembly systems. However, the more complicated a system of interest, the more difficult the interpretation in the SANS profile. In order to increase the reliability of structural analysis on a complicated system, it is desirable to obtain different kinds of structural information from the same sample simultaneously.

Observation of Protein and Lipid Membrane Structures in a Model Mimicking the Molecular-Crowding Environment of Cells Using Neutron Scattering and Cell Debris.

The interior of living cells is a molecular-crowding environment, where large quantities of various molecules coexist. Investigations into the nature of this environment are essential for an understanding of both the elaborate biological reactions and the maintenance of homeostasis occurring therein. The equilibrium states of biological macromolecular systems are affected by molecular-crowding environments unmatched by in vitro diluted environments; knowledge about crowding effects is still insufficient due to lack of relevant experimental studies.

Rheo-SANS study on relationship between micellar structures and rheological behavior of cationic gemini surfactants in solution.

Hypothesis: Gemini surfactant 12-2-12 (dimethylene-1,2-bis(dodecyl dimethylammonium bromide)) solutions are known to show shear thickening and thinning under salt-free conditions. Because the rheological behavior of the wormlike micelles formed by 12-2-12 in solution is related to their structure, we expected that changes to the precursor structure would affect their rheological behaviors. It is also important to understand the effect of the introduction of a spacer group in the 12-2-12 molecules on the rheological behavior and structure of the wormlike micelles under shear flow.

Restoration of Myoglobin Native Fold from Its Initial State of Amyloid Formation by Trehalose.

Organisms having tolerances against extreme environments produce and accumulate stress proteins and/or sugars in cells against the extreme environment such as high or low temperature, drying, and so forth. Sugars and/or polyols are known to prevent protein denaturation and enzyme deactivation. In particular, trehalose has received considerable attention because of its association with cryptobiosis and anhydrobiosis.

Sugar-Mediated Stabilization of Protein against Chemical or Thermal Denaturation.

The protective action of sugars against the denaturation of myoglobin was clarified by X-ray and neutron scattering methods. Different types of sugars such as disaccharides (trehalose, sucrose) and monosaccharides (glucose, fructose) were used. Experimental data and theoretical simulation based on three different solvation models (preferential solvation model, nonpreferential solvation model, and preferential exclusion (hydration) model) indicated that sugar molecules were preferentially or weakly excluded from the protein surface and preserved the native protein hydration shell.

Direct Evidence for the Effect of Glycerol on Protein Hydration and Thermal Structural Transition.

The mechanisms of protein stabilization by uncharged solutes, such as polyols and sugars, have been intensively studied with respect to the chemical thermodynamics of molecular crowding. In particular, many experimental and theoretical studies have been conducted to explain the mechanism of the protective action on protein structures by glycerol through the relationship between hydration and glycerol solvation on protein surfaces. We used wide-angle x-ray scattering (WAXS), small-angle neutron scattering, and theoretical scattering function simulation to quantitatively characterize the hydration and/or solvation shell of myoglobin in aqueous solutions of up to 75% v/v glycerol.

Dynamical Behavior of Hydration Water Molecules between Phospholipid Membranes.

The dynamical behavior of hydration water sandwiched between 1,2-dimyristyl-sn-glycero-3-phosphocholine (DMPC) bilayers was investigated by quasi-elastic neutron scattering (QENS) in the range between 275 and 316 K, where the main transition temperature of DMPC is interposed. The results revealed that the hydration water could be categorized into three types of water: (1) free water, whose dynamical behavior is slightly different from that of bulk water; (2) loosely bound water, whose dynamical behavior is 1 order of magnitude slower than that of the free water; and (3) tightly bound water, whose dynamical behavior is comparable with that of DMPC molecules. The number of loosely bound and tightly bound water molecules per DMPC molecule monotonically decreased and increased with decreasing temperature, respectively, and the sum of these water molecules remained constant.

Contrast variation by dynamic nuclear polarization and time-of-flight small-angle neutron scattering. I. Application to industrial multi-component nanocomposites.

Dynamic nuclear polarization (DNP) at low temperature (1.2 K) and high magnetic field (3.3 T) was applied to a contrast variation study in small-angle neutron scattering (SANS) focusing on industrial rubber materials.

Spatial arrangement and functional role of α subunits of proteasome activator PA28 in hetero-oligomeric form.

A major form of proteasome activator PA28 is a heteroheptamer composed of interferon-γ-inducible α and β subunits, which share approximately 50% amino acid identity and possess distinct insert loops. This activator forms a complex with the 20S proteasome and thereby stimulates proteasomal degradation of peptides in an ATP-independent manner, giving rise to smaller antigenic peptides presented by major histocompatibility complex class I molecules. In this study, we performed biophysical and biochemical characterization of the structure and function of the PA28 hetero-oligomer.