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Tadpole-type amphiphilic dendrimers featuring a hexadecyl chain and two or three poly(amidoamine) dendrons (C 16 - m denG n , where m is the number of dendron scaffolds (2 or 3) and n is the dendron (den) generation (G) number (1, 2, 3, 4, or 5)) were synthesized using hexadecylamine or N -hexadecylethylenediamine as central scaffolds. These dendrimers were characterized by acid-base titration, surface tension, pyrene fluorescence, static light scattering (SLS), and small-angle neutron scattering (SANS), and showed clear breakpoints in their surface tension vs. concentration plots. This behavior was indicative of adsorption at the air/water interface and micelle formation in solution despite the bulky dendron structure (e.g., generations 3–5), contrasting the behavior of conventional surfactants. Contrary to our expectation, the C 16 - m denG n dendrimers could be densely packed at the air/water interface owing to enhanced hydrogen bonding between amide groups in the case of higher generation numbers. Furthermore, the above dendrimers formed spherical micelles in solution at a concentration of 5.00 mmol dm −3 (pH 9), regardless of the dendron generation number. As the generation number was increased to 4 for C 16 -2denG n and 3 for C 16 -3denG n , aggregates of spherical micelles were observed. The radius of gyration of C 16 - m denG n dendrimers was estimated as 2.0–2.5 nm, being almost independent of the hydrophilic dendron size.

Single-alkyl chain-containing amphiphilic oligomers with a terminal alkyl chain and several sugar side chains (i.e., C n -mGEMA, where n represents alkyl chain lengths of 12 or 16 and m represents the polymerization degree of glycosyloxyethyl methacrylate (GEMA) units of 3.0–7.1), and multi-alkyl chain-containing amphiphilic oligomers with several sugar side chains (i.e., xC12-mGEMA, where x represents the average number of alkyl chains and x–m is 0.2–6.6, 1.8–4.7, and 3.4–3.7), were synthesized via the radical oligomerization of one or two monomers in the presence of alkanethiol or 2-aminoethanethiol hydrochloride. Surface tension, pyrene fluorescence, and small-angle neutron scattering (SANS) measurements were used to characterize the solution properties of the oligomers and the nanostructures of their aggregates. Both amphiphilic oligomers are highly efficient in reducing the surface tension of water (42–48 mN m−1 for C n -mGEMA and 36–46 mN m−1 for xC12-mGEMA), despite the relatively large structures of the hydrophilic parts in sugar GEMA units. The critical micelle concentration (CMC) of C n -mGEMA and xC12-mGEMA increased with an increase in the degree of polymerization for hydrophilic GEMA units and a decrease in the alkyl chain length. The results of SANS determined that C n -mGEMA formed prolate ellipsoid micelles with a radius of 1.96 nm and an axial ratio of 1.58 for a low degree of polymerization (m = 3.0) in solution. However, the radius decreased to 1.33 nm and the axial ratio increased to 5.04 as the degree of polymerization of the amphiphilic oligomers increased to m = 7.1, indicating structural transformation to an asymmetric ellipsoid. On the other hand, the structure of the aggregates formed by xC12-mGEMA changed from ellipsoidal to an ellipsoidal cylinder shape with increasing number of alkyl chains, i.e., decreasing the number of GEMA units.

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. Polarized infrared spectroscopy is able to provide information about the molecular structure, concentration, and orientation of each chemical species in a system. In order to utilize these advantages of polarized infrared spectroscopy, a simultaneous measurement system was built by incorporating a Fourier transform infrared (FTIR) spectrometer into a time-of-flight small angle neutron scattering instrument covering a wide Q range. Using this system, simultaneous measurements of wide- and small-angle neutron scattering and polarized FTIR spectroscopy was realized for the first time.

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. Fullerenes, which improve the resistance to oxidation decomposition, were incorporated in the membranes. The fullerenes seem to be chiefly located in the amorphous regions of the samples, and do not influence the formation and evolution of the morphologies in the polymer films, as no significant differences were observed in the SANS patterns compared to the fullerenes-free s-sPS membranes, which were investigated in a previous study. The use of uniaxially deformed film samples, and neutron contrast variation allowed for the identification and characterization of different structural levels with sizes between nm and &mu, m, which form and evolve in both the dry and hydrated states. The scattering length density of the crystalline regions was varied using the guest exchange procedure between different toluene isotopologues incorporated into the sPS lattice, while the variation of the scattering properties of the hydrated amorphous regions was achieved using different H2O/D2O mixtures. Due to the deformation of the films, the scattering characteristics of different structures can be distinguished on specific detection sectors and at different detection distances after the sample, depending on their size and orientation.

The structure-property relationship of an elastic physical gel, obtained by simply quenching syndiotactic polypropylene (sPP)/decahydronaphthalene solution with liquid nitrogen, was investigated based on small-angle neutron scattering (SANS) analysis. The SANS analysis revealed that sPP nanocrystals with a constant radius of 4-5 nm existed in the sPP gels regardless of the sPP concentration, whereas the correlation length of the nanocrystals drastically decreased from ∼130 to ∼20 nm upon increasing the sPP concentration from 2 to 12 wt%. The volume fraction and the number density of the sPP nanocrystals increased monotonously with the increase in the sPP concentration. The rheological properties and the melting behavior of the quenched sPP gels were highly consistent with the number density of the nanocrystals calculated from the SANS analysis, strongly suggesting that the sPP nanocrystals actually worked as crosslinking points by inducing elasticity in the quenched sPP gels.

In the room-temperature ionic liquid (IL) of 1-methyl-3-octylimidazolium bis(trifluoromethylsulfonyl)amide ([C8mim][TFSA]), the complex formation of Ni2+ with molecular liquids (MLs), dimethyl sulfoxide (DMSO), methanol (MeOH), and acetonitrile (AN), has been examined using ultraviolet (UV)-visible spectroscopy. The overall stability constants log βn, enthalpies , and entropies of the equilibria have been determined to elucidate the mechanism of complex formation. From a comparison of such thermodynamic parameters of the present [C8mim][TFSA] systems with those of the previous systems of 1-ethyl-3-methylimidazolium-based IL, [C2mim][TFSA], the effects of the octyl chain of the imidazolium cation, [C8mim]+, on the complex formation of Ni2+ with MLs have been demonstrated. In [C8mim][TFSA]-ML systems, more stable complexes are formed with MLs in the sequence of ANDMSO ≫ MeOH. This sequence differs from that of DMSO ≫ ANMeOH in [C2mim][TFSA]. For the AN systems, the stabilities of [Ni(an)n] in [C8mim][TFSA] are higher as compared to those in [C2mim][TFSA]. In contrast, for the DMSO systems, [Ni(dmso)n] is less stable in the IL with the longer alkyl chain than that in the IL with the shorter chain. The dependence of the alkyl chain length on the stabilities of [Ni(meoh)n] is the least significant among the three MLs. These varieties of the stabilities of Ni2+ complexes with the MLs have been interpreted from the thermodynamic parameters, together with the static interactions in the [C8mim][TFSA]-ML and [C2mim][TFSA]-ML solvents observed by means of 1H and 13C NMR, small-angle neutron scattering (SANS), and infrared (IR) with an ATR diamond prism.

The detailed structure of a nanogel formed by self-association of cholesterol-bearing pullulans (CHPs) was determined by contrast variation small-angle neutron scattering. The decomposition of scattering intensities into partial scattering functions of each CHP nanogel component, i.e., pullulan, cholesterol, and the cross-term between the pullulan and the cholesterol, allows us to investigate the internal structure of the nanogel. The effective spherical radius of the skeleton formed by pullulan chains was found to be 8.1 ± 0.3 nm. In the CHP nanogel, there are about 19 cross-linking points where a cross-linking point is formed by aggregation of trimer cholesterol molecules, and the spatially inhomogeneous distribution of the cross-linking points in the nanogel can be represented by the mass fractal dimension of 2.6. The average radius of gyration of the partial chains can also be determined to be 1.7 ± 0.1 nm by analyzing the extracted cross-correlation between the cross-linker and the tethered polymer chain quantitatively, and the size agrees with the value assuming random distribution of the cross-linkers on the chains. As the result, the complex structure of the nanogels is coherently revealed at the nanoscopic level.

2-(2'-Hydroxyphenyl)benzimidazole derivatives (X-HBIs), modified by various substituents X (X=H, CH3, OH, OCH3, NO2, NHCOCH3, NH2, N(CH3)2), were synthesized and their fluorescent behaviors and equilibriums in aqueous solution were studied. Strong fluorescence attributed to the tautomer emission was observed in aqueous solution at pH 7.4. The fluorescence intensities of the X-HBIs were enhanced selectively by addition of Zn(2+) but not by addition of Na(+), K(+), Mg(2+), Ca(2+), Mn(2+), Fe(2+), Co(2+), Ni(2+), and Cu(2+). Additionally, the effective ratiometric fluorescence response to Zn(2+) addition was observed in 5-NH2-HBI and 5-N(Me)2-HBI. The pH-titration and speciation studies proved that the X-HBIs have two or three protonation equilibriums and one complexation equilibrium corresponding to the formation of the [Zn(X-HBI)](+) complex. Further structural studies using extended X-ray absorption fine structure analyses and density functional theory calculations identified the dominant Zn(2+) species as the [Zn(HBI)(H2O)3](+) complex in aqueous solution. Based on the substituent effect on the fluorescence properties of X-HBIs and their Zn(2+) complexes in aqueous solution, the maximum fluorescence excitation and fluorescence wavelengths of both the tautomeric form and the Zn(2+) complexes were dependent on the Hammett substituent constants of X, which was attributed to the change of the π-π* energy gap of HBI by introduction of the substituent.

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. This study focuses on the restoration of acid-denatured amyloid transition of myoglobin by trehalose. Myoglobin is known to proceed amyloidogenic reaction under denaturation conditions. We found that acid-denatured myoglobin at an initial process of amyloidogenic reaction (helix-to-sheet transition followed by oligomerization) at 25 °C was substantially restored to its native structure by trehalose. This action was prominent during the early stage of amyloid formation. Recent results showed that sugars are preferentially excluded from the protein surface to preserve its hydration shell and stabilize the protein structure against chemical and thermal denaturation. Therefore, the present results suggest that trehalose will restore the tightly bound water molecules around the hotspot (G-helix) of myoglobin on the amyloid transition by its intrinsic preservative action of the native hydration shell against denaturation. The present finding on the restorative action by trehalose could provide new insights into protein folding and amyloidosis.

By using wide-angle X-ray scattering (WAXS), small-angle neutron scattering, and theoretical scattering function simulation, we have clarified the effect of glycerol on both the thermal structure transition and the hydration-shell of myoglobin. At the glycerol concentration, ≤ ∼40 % v/v, the decreasing tendency in the maximum dimension and the radius of gyration was observed by X-ray scattering. The neutron scattering result using the inverse contrast variation method directly shows the preservation of the hydration-shell density at the concentration ≤ ∼40 % v/v. This phenomenon is reasonably explained by the preferential exclusion of glycerol from the protein surface to preserve the hydration shell, as suggested by the previous studies. While, at the concentration, ≥ 50 % v/v, the opposite tendency was observed. It suggests the preferential solvation (partial preferential penetration or replacement of glycerol into or with hydration-shell water surrounding the protein surface) occurs at the higher concentration. The observed WAXS scattering data covers the distinct hierarchical structural levels of myoglobin structure ranging from the tertiary structure to the secondary one. Therefore, we have clarified the effect of glycerol on the thermal structural stability myoglobin at different hierarchical structural levels separately. Against the temperature rise, the structural transition temperatures for all hierarchical structural levels were elevated. Especially, the tertiary structure of myoglobin was more stabilized compared with the internal-structure and the helix-to-cross transition. It suggests that the protective action of glycerol on protein structures essentially results from the preservation of the preferential hydration-shell of proteins.

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. At glycerol concentrations below ∼40% v/v, the preservation of the hydration shell was dominant, which was reasonably explained by the preferential exclusion of glycerol from the protein surface (preferential hydration). In contrast, at concentrations above 50% v/v, the partial penetration or replacement of glycerol into or with hydration-shell water (neutral solvation by glycerol) was gradually promoted. WAXS results quantitatively demonstrated the neutral solvation, in which the replacement of hydrated water by glycerol was proportional to the volume fraction of glycerol in the solvent multiplied by an exchange rate ( β ≤ 1). These phenomena were confirmed by small-angle neutron scattering measurements. The observed WAXS data covered the entire hierarchical structure of myoglobin, ranging from tertiary to secondary structures. We separately analyzed the effect of glycerol on the thermal stability of myoglobin at each hierarchical structural level. The thermal transition midpoint temperature at each hierarchical structural level was raised depending on the glycerol concentration, with enhanced transition cooperativeness between different hierarchical structural levels. The onset temperature of the helix-to-cross β -sheet transition (the initial process of amyloid formation) was evidently elevated. However, oligomerization connected to fibril formation was suppressed, even at a low glycerol concentration.

The structures of micelles and microemulsions consisting of polyglycerol polyricinoleate (PGPR) were investigated by small-angle X-ray scattering (SAXS) and rheological measurements. The SAXS results show that amphiphilic PGPR molecules form stable micelles in glycerol. When vitamin E is added to the PGPR micelles, it is encapsulated in the micelles and forms an emulsion. These micelles are stable towards mechanical shearing up to a shear rate of 1000 s-1, with shear thinning occurring in the emulsion above 100 s-1, indicating that the emulsion may undergo break up by shearing, but recovers the structure by releasing shear strain.

The effect of crystal morphology, such as the crystallinity and lamellar structure, on the radiation-induced graft polymerization of styrenesulfonate ethyl ester (E4S) onto poly(ether ether ketone) PEEK films was evaluated. The PEEK films possessing crystallinities ranging from 11 to 32% were irradiated with 30–150 kGy, and the graft polymerization was performed in an E4S/1,4-dioxane solution at 80 °C. For the PEEK films with crystallinities between 11 and 26%, the graft polymerization proceeded and reached grafting degrees of up to 70%, whereas for those having crystallinities higher than 26%, the reaction barely proceeded. The concentration of phenoxy radicals that initiated the graft polymerization in the irradiated PEEK films was constant over the entire range of crystallinity (11–32%). On the other hand, in the small-angle X-ray scattering (SAXS) profiles, a discontinuous change in the peak intensity at Q = 0.44 nm −1 , which corresponds to a lamellar spacing of 14 nm, was observed at a crystallinity of approximately 26%; namely, the PEEK films with a crystallinities greater than 26% exhibited prominent anisotropic scattering in the drawing direction. Judging from the above results, it can be concluded that the graft polymerization of styrene derivatives onto the PEEK films was affected by the formation of oriented lamellar structures that inhibited monomer diffusion into the films.

We investigated the growth mechanisms of wormlike micelles formed by star-type trimeric surfactant (3C(12)trisQ) with a hydrocarbon chain length of 12 in an aqueous solution. A 3C(n)trisQ molecule consists of three hydrocarbon chains and three hydrophilic groups connected by spacer chains, where n is the carbon number in the hydrocarbon chain. Our recent studies showed that the aggregates formed by 3C(12)trisQ exhibited sphere-to-rod transition and the growth of wormlike micelles in an aqueous solution in the absence of salt. We performed small-angle neutron scattering (SANS) and rheological measurements and investigated the aggregation behavior of 3C(12)trisQ with various surfactant volume fractions. All SANS profiles for the 3C(12)trisQ indicated peak-profiles in the q range of 0.02 A(-1) < q < 0.05 A(-1), where the magnitude of the scattering vector q is defined by q = 4π sin(θ/2)/λ (λ and θ represent the wavelength and scattering angle, respectively). These peaks were attributed to repulsive interparticle interactions between the micelles. The volume fraction dependence of the SANS peak-position was in agreement with the rheological behavior. These results suggest that 3C(12)trisQ shows sphere-to-rod transition and can produce wormlike micelles in the absence of salt. To determine the structural parameters quantitatively, model-fitting analysis was performed using a charged cylindrical or charged ellipsoidal particle scattering function. The radius, length, and number of water molecules per surfactant molecule (n(w)) inside the micelles were evaluated. The length increased and the n(w) value decreased with increasing φ, indicating that the growth of a wormlike micelle accompanies the extrusion of water from the micelle. The end-cap energies of star-type trimeric, gemini, and monomeric surfactants were evaluated from φ dependence of zero-shear viscosity. We found that wormlike micelles formed by 3C(12)trisQ exhibited a higher end-cap energy than gemini surfactant.

Small-angle scattering in a wide-Q range (4 × 10–3 to 1.5 nm–1) of polymer electrolyte membranes consisting of poly(styrenesulfonic acid) and cross-linked polytetrafluoroethylene (cPTFE–PEM) with various grafting degrees up to 36% was observed by focusing small-angle neutron scattering (FSANS), small-angle neutron scattering (SANS), and small-angle X-ray scattering (SAXS). The hierarchical structure of the PEM was characterized as being composed of conducting layers (graft domains) in lamellar stacks with 48–57 nm spacing on the surfaces of 480 nm diameter crystallites and ultrasmall structures with 1.7 nm correlation distance of the sulfonic acid groups in the conducting layers. The PEMs with grafting degrees less than 15% possessed only grafting domains in the amorphous layers of the lamellar stacks of cPTFE. An increase in the grafting degree up to 5% led to an increase in the lamellar spacing of 20%, while the lamellar spacing remained constant with grafting degrees above 5% because of crystalline res...

Genomic DNA in eukaryotes wraps around histone proteins to package into the limited space of cell nucleus. Since the precise structure of chromatin is not known in detail, attempts have been made to understand DNA–histone interaction and the associated self-organization behavior using synthetic model systems. Using small-angle X-ray and neutron scattering, here we show that the electrostatic attraction between DNA and polyamidoamine (PAMAM) dendrimer of generation nine (G9) led to the formation of beads-on-string structure, where DNA wrapped around the dendrimer tightly to yield the “chromatin-like fiber” composing of the interconnected “nucleosome-like particles”. A “stiff chromatin-like fiber model” and a “wormlike chromatin-like fiber model” were introduced to obtain the theoretical scattering patterns closely resembling the experimentally observed ones, from which the pitch length (P) of the DNA superhelix wrapping around the dendrimer and the interparticle distance (d) of the nucleosome-like particle...

This study involves the upgrade of a high-resolution position-sensitive detector (HR-PSD) installed on the small-angle neutron scattering spectrometer (SANS-U) at the Japan Atomic Energy Agency. By using both neutron lenses and the HR-PSD, the accessible low-Qlimit can be extended to the order of 10−4 Å−1[Qis the magnitude of the scattering vector defined byQ= (4π/λ)sinθ, where λ and 2θ are the wavelength and the scattering angle, respectively]. The HR-PSD consists of a cross-wired position-sensitive photomultiplier tube (PSPMT) and a commercial ZnS/6LiF scintillator. To improve the experimental efficiency of focusing small-angle neutron scattering (FSANS) experiments, a high-performance ZnS/6LiF scintillator developed at the Japan Atomic Energy Agency has been utilized. For the PSPMT and data-acquisition system installed on SANS-U, the thickness of the ZnS/6LiF scintillator was optimized by measuring the thickness dependence of the pulse-height spectra. Under the experimental conditions of SANS-U, the optimum thickness of the ZnS/6LiF scintillator (ZnS:6LiF = 2:1) was determined to be 0.433 mm by measuring the total counts and peak positions of the pulse-height spectra. Installation of the optimized ZnS/6LiF scintillator improved detection efficiency by 1.39 times over that of a commercial scintillator at the same level of background counts andQresolution in FSANS experiments.

The small-angle neutron scattering spectrometer SANS-U at the research reactor (JRR-3) of the Japan Atomic Energy Agency, Tokai, Japan, has been successfully upgraded. This major upgrade was undertaken in order to install a high-resolution position-sensitive detector consisting of a cross-wired position-sensitive photomultiplier tube combined with a ZnS/6LiF scintillator on the SANS-U spectrometer. Without changing the total length of the spectrometer, the aim was to extend the accessible low-Qlimit (Qis the magnitude of the scattering vector) and to shorten the measurement time by employing focusing small-angle neutron scattering (FSANS). By using both spherical MgF2biconcave lenses and the new high-resolution position-sensitive detector, the accessible low-Qlimit was extended from 2.5 × 10−3to 3.8 × 10−4 Å−1. As a result, SANS-U can continuously cover a wideQrange from 3.8 × 10−4to 0.35 Å−1with a wavelength of 7 Å. FSANS can be utilized not only to improve the accessible low-Qlimit but also to increase the intensity of incident neutrons passing through the sample in the conventionalQrange from 2.5 × 10−3to 0.35 Å−1. The use of `high-intensity' FSANS also allowed a reduction of the measuring time by approximately 1/3.16 by increasing the incident neutron intensity.

Radiation-induced graft polymerization of sulfo-containing styrene derivatives into crystalline poly(ether ether ketone) (PEEK) substrates was carried out to prepare thermally and mechanically stable polymer electrolyte membranes based on an aromatic hydrocarbon polymer, so-called “super-engineering plastics”. Graft polymerization of the sulfo-containing styrene, ethyl 4-styrenesulfonate (E4S) into a high crystalline PEEK substrate (degree of crystallinity: 32%) hardly progressed, whereas graft polymerization into a low crystalline PEEK substrate (degree of crystallinity: 11%) gradually progressed, achieving a grafting degree of more than 50% after 72 h. Oxygen radicals appeared in the ESR spectra of irradiated PEEK films, indicating that graft polymerization initiates from the phenoxy radicals generated by scission of PEEK main chains and proceeds so as to yield block type grafts. The PEEK-based polymer electrolyte membrane (PEM) converted by aqueous hydrolysis of grafted films exhibited mechanical strength (100 MPa), being 88% of the original PEEK substrates. These mechanical properties of PEEK-based PEM are much higher than those of graft-type fluorinated PEM reported previously and almost three times higher than that of Nafion (35 MPa). Wide- and small-angle X-ray scattering (WAXS and SAXS) indicated that the graft polymerization was accompanied with recrystallization of the amorphous phase of PEEK substrate, the well known solvent-induced recrystallization of amorphous PEEK solids, to form a weak lamellar structure with 8 nm spacing. Complementary SAXS and small-angle neutron scattering (SANS) observations clearly showed that the graft-type PEEK membranes possessed ion channel domains with the average distance of 13 nm, being larger than that of Nafion. Furthermore, there was a micro-structure in the ion channels with the average distance of 1.8 nm.

Aspherical neutron lenses are discussed in detail as focusing elements for existing small-angle neutron scattering (SANS) diffractometers. The conceptual design can be obtained by analytical equations, while computer simulations provide the intensity distribution of the primary beam, which is strongly correlated with the instrumental resolution and the minimal momentum transferQ. For large illuminated sample/lens areas of 50 mm diameter the aspherical lens design is essential, while spherical lenses are limited toca20 mm diameter with a 60% spherical aberration for standard SANS experiments. Scattering experiments on different samples proved the applicability and revealed the resolution limits of the two lens types. From theoretical considerations it is proposed that lens cooling can be used to reduce the thermal diffuse scattering.

In order to visualize water generated in an operating polymer electrolyte fuel cell (PEFC), a neutron radiography (NR) apparatus, composed of a scintillator, optical mirrors and a CCD camera, was installed at a sample position of the focusing and polarized neutron small-angle scattering (SANS) spectrometer (SANS-J-II) at research reactor JRR-3 at Japan Atomic Energy Agency, Tokai, Japan. By combining SANS and NR, we aim to cover a wide length scale from nanometer to millimeter. The new method succeeded in detecting a spatial distribution of the water generated in individual cell elements; NR detected the water in a gas diffusion layer and a flow field, whereas SANS quantitatively determines the water content in a membrane electrode assembly (MEA).

Neutron diffraction measurements were carried out on H/ D isotopically substituted water in the low-density supercritical condition (T = 673 K, P = 26.3 MPa, and rho = 0.0068 molecules.A-3) in order to obtain direct information on the intermolecular partial structure functions, gHH inter(r), gOH inter(r), and gOO inter(r). In correspondence to the high-density supercritical water previously reported, the intermolecular nearest neighbor peaks in gHH inter(r), gOH inter(r), and gOO inter(r) are diffuse compared with the ambient ones. The nearest neighbor O...O distance (3.3 A) and its coordination number (2.6) were determined from the observed gOO inter(r). These results indicate that the orientational correlation between neighboring water molecules is considerably lost in low-density supercritical water. Small clusters involving a few water molecules are preferentially formed in low-density supercritical water, which is consistent with results obtained by previous IR and NMR studies.

At 279, 287, 298, and 307 K the heterogeneity of acetonitrile–water mixtures in a range of acetonitrile mole fraction x AN from 0.2 to 0.6 has been evaluated in terms of Ornstein–Zernike correlation length, concentration and density fluctuations, and Kirkwood–Buff parameters obtained from small-angle neutron scattering (SANS) experiments. At 298 K the correlation lengths for CH 3 CN–D 2 O (D = 2 H) and CD 3 CN–H 2 O mixtures have shown that the heterogeneity of acetonitrile–water mixtures at x AN = 0.3 and 0.4 is most enhanced in the mole fraction range examined. With decreasing temperature from 307 to 279 K, the correlation length and the fluctuations for CH 3 CN–D 2 O mixtures at x AN = 0.3 and 0.4 most significantly rise in the mole fraction range. The Kirkwood–Buff parameters have revealed that both acetonitrile–acetonitrile and water–water interactions in acetonitrile–water mixtures at the same mole fractions remarkably increase with decreasing temperature, whereas acetonitrile–water interactions decrease. According to all the parameters estimated, a change in mixing state of acetonitrile–water mixtures with lowering temperature was discussed.

SANS-J (a pinhole small-angle neutron scattering spectrometer at research reactor JRR3, Tokai, Japan) was reconstructed as a focusing and polarized neutron small-angle scattering spectrometer (SANS-J-II). By employing focusing lenses of a biconcave MgF2 crystal or of a sextupole permanent magnet and a high-resolution photomultiplier, the minimum accessible magnitude of the scattering vector qmin was improved from 3 × 10−3 A−1 to an ultra-small-angle scattering (USAS) of 3 × 10−4 A−1. Compared with a Bonse–Hart double-crystal method, the advantages of focusing USAS are the efficient detection of anisotropic USAS with an area detector, an improvement in q resolution Δq/q at conventional magnitudes of the scattering vector q ~ 10−3 A−1 and a gain in neutron flux in the conventional q region of q ~ 10−3 A−1.

In order to extend an upper q-limit [q is the magnitude of the scattering vector q, defined by q = (4π/λ)sinθ, where λ and 2θ are the wavelength and the scattering angle, respectively], high-angle 3He sub-detectors were installed on a focusing and polarized neutron small-angle scattering spectrometer (SANS-J-II) at JRR-3, Tokai, Japan. Consequently, the upper q-limit was improved from 0.2 to 2.0 A−1. To quantitatively discriminate spin incoherent scattering from hydrogen or to perform nuclear spin polarization contrast variation, a remanent supermirror analyser is also available on the high-angle sub-detector. By combining a focusing ultra-small-angle scattering, realised by compound and/or magnetic lens and high-resolution area detector, SANS-J-II is able to cover from 3 × 10−4 to 2.0 A−1 (four orders of magnitude of q), which benefits investigation of hierarchically ordered systems, found widely in hard, soft and bio-materials.

We have constructed a focusing-geometry small-angle neutron scattering (FSANS) instrument, SANS-J-II, with two kinds of neutron focusing device: a series of compound refractive lenses made of MgF2 and a magnetic neutron lens based on an extended Halbach-type sextupole magnet. In this study, we investigated the performance of the FSANS instrument with the magnetic neutron lens. The intensity distribution of a direct neutron beam focused on the detector plane by the magnetic neutron lens had a ratio of the peak height to the background level of \sim\!6\times 10^4 for a polarized neutron beam with a polarization degree of \sim \!0.99. It is found that a minimum value of the measurable q range [where q is the modulus of the scattering vector and is defined as q = (4\pi/\lambda)\sin(\theta/2), where \theta is the scattering angle and \lambda is the neutron wavelength], q_{\rm min}, of 6.5 \times 10^{-4} A−1 can be achieved by the FSANS instrument with the magnetic neutron lens using neutrons with \lambda = 6.6 A and \Delta \lambda/\lambda = 0.13 for the full width at half maximum.

To address the question as to how small-angle scattering is effectively applied to the cell, i.e., ahierarchically ordered system comprising multi-components of macro and small molecules, the size ofwhich ranges from 100 μm to several μm, we reconstructed SANS-J (pinhole small-angle neutronscattering spectrometer at research reactor JRR3, Tokai) to focusing & polarized neutron small-anglespectrometer (SANS-J-II), by employing focusing neutron lenses and high resolution photomultiplier.Consequently, an accessible minimum wave number qmin was improved from 3×10-3 A-1 to mediumultra-small angle scattering of 3×10-4 A-1. The focusing USANS method, thus developed, is crucialto fill the gap in wave number q between those covered by a double crystal method and by a conventionalpin-hole method.

By combined use of time-of-flight small-angle neutron scattering (SANS) and synchrotron radiation small-angle X-ray scattering (SAXS), we investigated aggregation behaviors of gemini-type amphiphilic dendrimers (2C12-2denGn, where n denotes the generation number) in an aqueous solution with varying generation (n). 2C12-2denGn consists of two poly(amidoamine) (PAMAM) dendrons and C12 hydrocarbon chains connected by spacer chains. We found that the radius of gyration (Rg) evaluated from the SANS profiles for the 2C12-2denGn solution was nearly constant with n, which was remarkably different from that of dendrimer particles. In addition, model-fitting analysis for the SANS and the SAXS results was carried out using a theoretical scattering function of the polydisperse core-shell sphere model. With increasing n, the core radius gradually decreased, whereas the shell thickness increased. Although the hydrophilic dendron portion was much balky, the results suggested that 2C12-2denGn formed small spherical micelles with an overall radius of about 31 A. This is due to efficient arrangements of both dendrons and hydrocarbon chains in an aqueous solution.

J-PARC Center, Japan Atomic Energy Agency (JAEA), Tokai, Ibaraki 319-1195, Japan Research Center for Neutron Science and Technology, Comprehensive Research Organization for Science and Society (CROSS), Tokai, Ibaraki 319-1106, Japan J-PARC Center, High Energy Accelerator Research Organization (KEK), Tsukuba, Ibaraki 305-0801, Japan Research Reactor Institute, Kyoto University (KURRI), Kumatori, Osaka 590-0494, Japan

2-(2'-Hydroxyphenyl)benzimidazole derivatives (X-HBIs), modified by various substituents X (X=H, CH3, OH, OCH3, NO2, NHCOCH3, NH2, N(CH3)2), were synthesized and their fluorescent behaviors and equilibriums in aqueous solution were studied. Strong fluorescence attributed to the tautomer emission was observed in aqueous solution at pH 7.4. The fluorescence intensities of the X-HBIs were enhanced selectively by addition of Zn(2+) but not by addition of Na(+), K(+), Mg(2+), Ca(2+), Mn(2+), Fe(2+), Co(2+), Ni(2+), and Cu(2+). Additionally, the effective ratiometric fluorescence response to Zn(2+) addition was observed in 5-NH2-HBI and 5-N(Me)2-HBI. The pH-titration and speciation studies proved that the X-HBIs have two or three protonation equilibriums and one complexation equilibrium corresponding to the formation of the [Zn(X-HBI)](+) complex. Further structural studies using extended X-ray absorption fine structure analyses and density functional theory calculations identified the dominant Zn(2+) species as the [Zn(HBI)(H2O)3](+) complex in aqueous solution. Based on the substituent effect on the fluorescence properties of X-HBIs and their Zn(2+) complexes in aqueous solution, the maximum fluorescence excitation and fluorescence wavelengths of both the tautomeric form and the Zn(2+) complexes were dependent on the Hammett substituent constants of X, which was attributed to the change of the π-π* energy gap of HBI by introduction of the substituent.

By employing focusing lenses of sextupole permanent magnet and biconcave MgF2 crystal, and high-resolution photomultiplier, SANS-J (pinhole small-angle neutron scattering spectrometer at research reactor JRR3, Tokai) was reconstructed to focusing and polarized neutron ultra-small-angle scattering spectrometer (SANS-J-II). Consequently, an accessible minimum wave number qmin was improved from 3×10−3 A−1 to 3×10−4 A−1. Furthermore, we added 3He sub-detectors with an analyzer super mirror at a sample position. With this setup, we perform polarization analysis at high q (>0.2 A−1) in order to quantitatively discriminate spin incoherent scattering from hydrogen or to perform spin contrast variation, by a dynamic nuclear polarization method (>0.2 A−1).

New superionic glasses (CuI)x(AgPO3)1−x with x=0.1, 0.2 and 0.3 have been prepared by rapid quenching method. Neutron diffraction experiments have been performed by a HIT-II spectrometer at the Neutron Spallation Source, KEK, Japan. A small first diffraction peak at low Q around 0.8 A was observed in the structure factor for x=0.2 and x=0.3, but for x=0.1 it shows only a shoulder that is similar to the undoped glass AgPO3. Three new peaks appear at the radial distribution function of (CuI)x(AgPO3)1−x at ∼ 1.9, 2.7 and 3.4 A, that may correspond to the Cu-O, Cu-I and Cu-Cu pair correlations, respectively. Those peaks increase with the amount of CuI. These results indicate that there are two different kinds of Cu atoms. Cu-I bond in the glass is very similar to that in crystalline α-CuI, and Cu-O bond is very similar to that in Cu2O insulating crystal.

Functions of mammalian cell membrane microdomains being rich in glycosphingolipids, so-called rafts, are now one of the current hot topics in cell biology from the intimate relation to cell adhesion and signaling. However, little is known about the role of glycosphingolipids in the formation and stability of the domains. By the use of the inverse contrast variation method in small-angle neutron scattering (SANS), combined with small-angle x-ray scattering (SAXS) and dynamic light scattering (DLS), we have determined an asymmetric internal structure of the bilayer of the small unilamellar vesicle (SUV) of monosialoganglioside (G(M1))-dipalmitoylphosphatidylcholine (DPPC) mixture ([G(M1)]:[DPPC] = 0.1:1). A direct method using a shell-model fitting with a size distribution function describes consistently all experimental results of SANS, SAXS, and DLS. We have found that G(M1) molecules predominantly localize at SUV outer surface to form a highly hydrophilic layer which is dehydrated with the rise of temperature from 25 degrees C to 55 degrees C accompanied by the conformational change of the oligosaccharide chains. The average SUV size determined is approximately 200 A, which is comparable to the reported value 260 +/- 130 A of glycosphingolipids microdomains. The present results suggest that the preferential asymmetric distribution of gangliosides is essential to define the size and stability of the domains.

In the present study using a high-intensity X-ray beam from a third-generation synchrotron radiation source, it is demonstrated that a wide-angle X-ray scattering (WAXS) profile from several globular proteins in solution can reflect not only the overall structures (approximately 300 A distance resolution) but also intramolecular structures ranging to secondary structures (approximately 2.5 A distance resolution). The proteins treated in the present experiments are classified as different types of structure categories, namely, as all-alpha, all-beta and alpha + beta proteins. Here the full-range experimental scattering curves are compared with the theoretical curves, suggesting a further availability of the SR-WAXS method for studies of structure hierarchy and the function of proteins in solutions.

The neutron instruments suite, installed at the spallation neutron source of the Materials and Life Science Experimental Facility (MLF) at the Japan Proton Accelerator Research Complex (J-PARC), is reviewed. MLF has 23 neutron beam ports and 21 instruments are in operation for user programs or are under commissioning. A unique and challenging instrumental suite in MLF has been realized via combination of a high-performance neutron source, optimized for neutron scattering, and unique instruments using cutting-edge technologies. All instruments are/will serve in world-leading investigations in a broad range of fields, from fundamental physics to industrial applications. In this review, overviews, characteristic features, and typical applications of the individual instruments are mentioned.