[Show abstract][Hide abstract] ABSTRACT: Supersaturation of a solution system is a metastable state containing more solute than can be normally solubilized. Moreover, this condition is thermodynamically important for a system undergoing a phase transition. This state plays critical roles in deposition morphology in inorganic, organic, polymer and protein solution systems. In particular, microscopic solution states under supersaturated conditions have recently received much attention. In this report, we observed the dynamic motion of individual ion-network domains (INDs) in a supersaturated sodium acetate trihydrate solution (6.4 M) by using microsecond time-resolved and high accuracy (picometre scale) X-ray observations (diffracted X-ray tracking; DXT). We found that there are femto-Newton (fN) anisotropic force fields in INDs that correspond to an Angstrom-scale relaxation process (continuous expansion and compression) of the INDs at 25 μs time scale. The observed anisotropic force-field (femto-Newton) from DXT can lead to new explanations of how material crystallization is triggered. This discovery could also influence the interpretation of supercooling, bio-polymer and protein aggregation processes, and supersaturated systems of many other materials.
[Show abstract][Hide abstract] ABSTRACT: The molecular aggregation structure evolution during uniaxial stretching deformation and the uniaxial tensile mechanical properties for an environmentally benign and biodegradable segmented poly(urethane-urea) (SPUU) elastomer based on an α-amino acid lysine-based diisocyanate (LDI) was investigated. The performance was compared with a conventional SPUU elastomer consisting of a symmetric aliphatic short chain diisocyanate (1,4-butane diisocyanate). Both SPUUs contain a 1,4-butanediamine chain extender and poly(ε-caprolactone) soft segments. The evolution of molecular aggregation structure during stretching was monitored using in-situ simultaneous small-angle X-ray scattering and wide-angle X-ray diffraction. The LDI-based SPUU film contains weakly aggregated, disordered hard segment domains that readily dissociate upon mechanical deformation. The permanent deformation through fragmentation of the hard segment domains and strain-induced crystallization are associated with the low strength and large hysteresis loss of the LDI-based SPUU.
[Show abstract][Hide abstract] ABSTRACT: The synergistic interactions between the α-amine and the carboxylic acid in an amino acid have recently been studied as bio-based zwitterions. Here, we report a new amphiphilic polymer containing glutamic acid grafted to the end of a dodecyl polymer side chain, which contains the α-amine and the γ-carboxylic acid of the glutamic acid moiety. The polymer self-assembled into a multilayered structure in the thin film, and the glutamic acid moieties in the polymer side chains were exposed to the polymer film/water interface. Annealing the sample enhanced the formation of a well-oriented lamellar structure in the films. Due to the presence of the glutamic acid moieties at the interface, the surface charge was controllable by pH in buffer solutions, resulting in zwitterionic character at neutral pH. It has been widely accepted that zwitterionic surfaces can exhibit non-fouling for proteins. Interestingly enough, the polymer film showed charge-selective protein adsorption since the synergistic interaction between the α-amine and the γ-carboxylic acid was weaker than conventional amino acid-based zwitterionic systems. This is due to the separated state of the functional groups by a three carbon spacer. This journal is
No preview · Article · Oct 2015 · Polymer Chemistry
[Show abstract][Hide abstract] ABSTRACT: A series of zwitterionic polyelectrolytes poly[3-(N-2-methacryloyloxyethyl-N,N-dimethyl)ammonatopropanesulfonate] (PMAPS) with a wide range of weight-average molecular weight (Mw) between 5.5 × 103 and 1.6 × 106 g mol-1 with narrow molecular weight distribution (Mw/Mn = 1.07-1.19) were thoroughly characterized in aqueous NaCl solutions for salt concentration (Cs) over a range from theta Cs (0.074 M) to 1.0 M by synchrotron radiation small-angle X-ray scattering (SAXS), light scattering, and viscometry at 25 °C. To determine the chain stiffness parameter (λ-1) and the excluded-volume strength (B) of PMAPS in an aqueous NaCl solution, SAXS profiles and the Mw dependences of the radius of gyration, the second virial coefficient, the interpenetration function, the hydrodynamic radius, and the intrinsic viscosity for PMAPS were analyzed on the basis of the (un)perturbed cylindrical wormlike chain model. The experimental λ-1 value for PMAPS chains in aqueous NaCl solutions barely decreased but was almost constant with the increasing Cs, whereas the value of B was increased gradually with the increasing Cs. Thus, the dominant factor for the chain dimension of PMAPS in aqueous NaCl solutions was the long-range interaction (i.e., B) than the short-range interaction (i.e., λ-1). The observed Cs dependences of λ-1 and B for PMAPS chains in aqueous NaCl solutions were fairly described by the theories of the polyampholyte with the nonrepulsive, the repulsive, and the attractive electrostatic interactions.
[Show abstract][Hide abstract] ABSTRACT: We have investigated the inner structure of shear-induced precursor of shish kebab of isotactic polystyrene (iPS) above the nominal melting temperature Tm using microbeam wide-angle X-ray scattering. We first studied the effects of the shear rate on the inner structure and found that the crystallinity in the precursor increased with the shear rate while the crystallite size was independent of that. This was explained in terms of effects of chain entanglements on shear-induced crystallization. We also studied effects of annealing below the nominal melting temperature Tm and found no changes in the crystallites size before and after the annealing, suggesting that the crystallites did not grow into shishs during the annealing below Tm although the kebabs grew.
[Show abstract][Hide abstract] ABSTRACT: The chain stiffness and local chain conformation of atactic poly(α-methylene-γ-butyrolactone) (PMBL), which is a side chain cyclic structural analog of poly(methyl methacrylate) (PMMA), with a weight-average molecular weight (Mw) ranging from 2.8 × 103 to 2.6 × 106 in N,N-dimethylformamide (DMF) and γ-butyrolactone (GBL) were characterized by size exclusion chromatography with a multi-angle light-scattering detector (SEC-MALS) and synchrotron radiation small-angle X-ray scattering (SAXS). Based on the Kratky-Porod worm-like chain model, the scattering functions and the Mw dependence of z-average root-mean-square radius of gyration z1/2 yielded the Kuhn segment lengths λ−1, the diameter of the PMBL chains d, and the excluded-volume strengths in DMF and GBL. The local conformation of atactic PMBL in DMF and GBL were slightly larger than those of atactic PMMA, due to the presence of the conformationally rigid lactone ring structure.
[Show abstract][Hide abstract] ABSTRACT: We observed the dynamic three-dimensional (3D) single molecule behaviour of acetylcholine-binding protein (AChBP) and nicotinic acetylcholine receptor (nAChR) using a single molecule tracking technique, diffracted X-ray tracking (DXT) with atomic scale and 100 μs time resolution. We found that the combined tilting and twisting motions of the proteins were enhanced upon acetylcholine (ACh) binding. We present the internal motion maps of AChBP and nAChR in the presence of either ACh or α-bungarotoxin (αBtx), with views from two rotational axes. Our findings indicate that specific motion patterns represented as biaxial angular motion maps are associated with channel function in real time and on an atomic scale.
[Show abstract][Hide abstract] ABSTRACT: We carried out synchrotron X-ray scattering experiments from four DNA supermolecules designed to form tetrapod shapes; these supermolecules had different sequences but identical numbers of total base pairs and each contained an immunostimulatory CpG motif. We confirmed that the supermolecules did indeed form the expected tetrapod shape. The sample that had the largest radius of gyration (Rg) induced the most cytokine secretion from cultured immune cells Structural analysis in combination with a rigid tetrapod model and an atomic scale DNA model revealed that the larger Rg can be ascribed to dissociation of the DNA double strands in the central connecting portion of the DNA tetrapod. This finding suggests that the biological activity is related to the ease with which single DNA strands can be formed.
No preview · Article · Aug 2014 · The Journal of Physical Chemistry B
[Show abstract][Hide abstract] ABSTRACT: We synthesized new calixarene-based lipids, denoted by CPCaLn, bearing choline phosphate (CP) group which is inverse phosphoryl choline (PC) structure. Small-angle X-ray scattering and multi-angle light scattering coupled with field flow fractionation showed that these lipids form monodisperse micelles with a fixed aggregation number and diameters of 1.9 and 2.6 nm for lipids bearing C3 and C6 alkyl tails, respectively. Furthermore, when CPCaLn was mixed with the fluorescein isothiocyanate (FITC)-bearing lipids and added to cells, the strong fluorescence was observed at 37 °C, but not at 4 °C, indicating that the micelles were taken up by the cells through endocytosis. Recent studies have shown that replacement of polymer-attached PC groups with CP groups markedly promotes cellular uptake, even though the surface charge is neutral. On the basis of the idea, CPCaLn micelles interacted with cells in the same way, suggesting that the micelles bearing CP groups are expected to use as carriers in drug delivery system.
[Show abstract][Hide abstract] ABSTRACT: For small-angle X-ray scattering (SAXS) in solution, absolute intensity calibration is an important step to estimate the number of electrons of the sample. In this study, the excess scattering length of 1-bromododecane dispersed in dodecane was determined using that of 1-chlorododecane in the same solvent. The deviation of the experimental values from theoretical calculations obtained using atomic factors was around 1%. It is suggested that the 1-chlorododecane–dodecane system constitutes a new calibration approach that is applicable to various materials over a large energy range generally used in SAXS measurements, and could be less complex and more reliable than conventional methods.
[Show abstract][Hide abstract] ABSTRACT: The simultaneous measurement of Fourier transform infrared (FTIR) transmission spectra and 2-dimensional wide-angle X-ray diffraction (WAXD) and small-angle X-ray scattering (SAXS) patterns has been performed successfully to investigate the hierarchical structure changes occurring in the stress-induced phase transition phenomenon of uniaxially oriented poly(tetramethylene terephthalate) film. The molar fraction of the β-crystal form, evaluated from the IR and WAXD data analyses, increased steeply in the plateru region of the stress–strain curve as already known well. The 2D SAXS data have revealed the remarkable and reversible change in the stacked lamellar structure just after the α-to-β phase transition was completed, where the tilting angle of the stacked lamellae measured from the draw axis of the oriented sample became zero, and the lamellar thickness increased due to the inclusion of amorphous region located in the boundary part of the crystalline lamellae. In parallel, the X-ray reflection spots in a wider diffraction angle region became diffuse in the observed WAXD pattern of the β form, indicating the packing disorder of the mechanically stressed chains. In this way, the simultaneous combination of the 3 different types of equipments has allowed us to deduce the detailed structural change from the various levels: the stress-induced α–β transition was found to occur not only with the remarkable changes in the molecular chain conformation and chain packing mode in the crystal lattice, but also with the large and reversible change in the lamellar stacking structure. The stress-induced changes in lamellar thickness and long period were simulated using a mechanical model with these hierarchical structure changes taken into account, giving relatively good reproduction of the observed data.
[Show abstract][Hide abstract] ABSTRACT: A novel calixarene amphiphilic molecule, denoted by CCaL3, was synthesized and found to form a spherical micelle consisting of 12 molecules at low pH in aqueous solution. Furthermore, uniform Au nanoparticles with 2.0 nm in diameter were synthesized in aqueous solution on the template consisting of the four cysteines of the upper rim of CCaL3. Asymmetric field flow fractionation coupled with light scattering showed that there was no dispersity in the CCaL3 micellar aggregation number. When AuCl4- ions were added into the CCaL3 micelle solution, induced circular dichroism (ICD) appeared, indicating appearance of the structural chirality of the CCaL3/AuCl4- complex. A combination of electron microscopy and small-angle X-ray scattering showed that helically coiled bilayer sheets were formed upon addition of AuCl4-. Subsequent reduction with the amine of cysteine moieties led to uniform Au nanoparticles formation with 2.0 nm in diameter on the micellar plate surface. The nanoparticle size was almost equal to the size of cavity constructed by the four cysteines on the calixarene upper rim, indicating that the growth of Au nanoparticles was spatially controlled by the host-guest interaction between the cysteines and Au.
[Show abstract][Hide abstract] ABSTRACT: Diffracted X-ray tracking (DXT) enables the tilting and twisting motions of single protein molecules to be monitored with micro- to milliradian resolution using a highly brilliant X-ray source with a wide energy bandwidth. We have developed a technique to monitor single molecules using gold nanocrystals attached to individual protein molecules using the BL28B2 beamline at SPring-8. In this paper we present the installation of a single toroidal X-ray mirror at BL28B2 to focus X-rays in an energy range of 10-20 keV (△E/E = 82% for an X-ray with a wide energy bandwidth). With this beamline we tracked diffraction spots from gold nanocrystals over a wide angle range than that using quasi-monochromatic X-rays. Application of the wide angle DXT technique to biological systems enabled us to observe the on-site motions of single protein molecules that have been functionalized in vivo. We further extend the capability of DXT by observing the fractional tilting and twisting motions of inner proteins under various conditions. As a proof of this methodology and to determine instrumental performance the intramolecular motions of a human serum albumin complex with 2-anthracenecarboxylic acid was investigated using the BL28B2 beamline. The random tilting and twisting intramolecular motions are shown to be directly linked to the movement of individual protein molecules in the buffer solution.
No preview · Article · Oct 2013 · The Review of scientific instruments
[Show abstract][Hide abstract] ABSTRACT: We investigated the molecular aggregation states, mechanical properties, and biodegradability of environmentally benign segmented polyurethane(urea)s [SPU(U)s], which contained bio-based monomers of an α-amino acid lysine-based diisocyanate (LDI). The SPU(U)s consisted of an aliphatic diisocyanate (LDI or 1,4-butanediisocyanate (BDI)), a chain extender (1,4-butanediamine (BDA) or 1,4-butanediol (BDO)), and a poly-ε-caprolactone (PCL) segment. Four SPU(U)s, LDI–BDA, LDI–BDO, BDI–BDA, and BDI–BDO, were prepared by a standard two-step prepolymer method. Fourier transformed infrared spectroscopy (FT-IR), differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), and small-angle X-ray scattering (SAXS) measurement indicated that the LDI-series SPU(U)s formed weakly aggregated hard segment domains, which readily dissociated under mechanical deformation and heating. The diamine chain extender, BDA, enhanced the stability of the hard segment domains, and the BDA-series SPU(U)s exhibited better mechanical properties than the BDO-series. The LDI-series SPU(U)s have notable biodegradability, and the BDI-based hard segments delayed the degradation rate because of the strongly segregated hard segment.
[Show abstract][Hide abstract] ABSTRACT: A series of poly[2-(methacryloyloxy)ethyltrimethylammonium chloride] (PMTAC) in aqueous NaCl solutions with a weight-average molecular weight (Mw) of between 6.0 × 103 and 1.5 × 105 were characterized by synchrotron radiation small-angle X-ray scattering (SAXS) and dynamic light scattering (DLS) measurements at 298 K. The hydrodynamic radius (RH) of PMTAC initially decreased with increasing salt concentration (Cs) and then leveled off at Cs = 0.5–1.0 M. The values of z-average root-mean-square radius of gyration (S2z1/2) simply increased with a decrease in Cs for Mw > 2 × 104 g/mol. In contrast, the values of S2z1/2 for Mw < 2 × 104 g/mol increased with an increase in Cs probably because of a change in local conformation of PMTAC chain. To study local chain conformation of PMTAC, scattering functions and Mw dependences of S2z1/2 and RH for PMTAC were analyzed in terms of the helical wormlike chain (HW) model which is a simple continuous elastic wire model with bending and torsional energies. The characteristic helix of the HW model in potential energy minimum for PMTAC clearly indicates that the local conformation is strongly influenced by the ionic strength of the solution.
[Show abstract][Hide abstract] ABSTRACT: We applied the microbeam two-dimensional small-angle X-ray scattering (2d-µSAXS) technique in order to characterize orientation of polystyrene (PS) microdomains as a function of the distance from the free surface of a sample sheet down to the surface facing to the substrate, for depth profiling for spontaneous perpendicular orientation of PS cylinders in the matrix of polyethylenebutylene (PEB) in a PS-b-PEB-b-PS triblock copolymer thick sheet as thick as ∼0.5 mm. It has been revealed that near the free surface the cylinders were randomly oriented down to ∼70 µm in depth. Although this might indicate that the surface effect, which preferentially dictates cylinders to be oriented parallel to the surface, can propagate for such a long distance, 70 µm is unusually huge as compared to the general knowledge of the surface effect propagating at most for 1 µm. Experimentally examining further, we finally conclude that the 2d-µSAXS depth profiling overestimates the surface effect. This unfavorable conclusion may be ascribed to surface roughness of the sample sheet subjected to the measurement, and in order to obtain a good result a big effort is required to prepare the surface as flat as possible.
No preview · Article · May 2013 · Macromolecular Symposia
[Show abstract][Hide abstract] ABSTRACT: This work demonstrates the anomalous crystal growth of isotactic polystyrene (iPS) in nanorod arrays with different rod sizes. At the bottom of the nanorods, the crystals in bulk film grow into nanorods along either the  or  direction parallel to the rod axis. On the top side of the nanorods, the polymer exhibits different orientations corresponding to weak or strong confinement. In the weaker confinement (bigger nanorods of 300 nm diameter), the crystals grow with the  direction along the nanorod, which is similar to the crystals developed in the radial of spherulite. In the stronger confinement (smaller nanorods of 65 nm diameter), the splaying of crystals in the rod is significantly suppressed, and the preferred growth direction of iPS crystals is kept in either the  or  direction. The precise control of polymer crystal orientation and crystallinity at a local scale opens important perspectives for the design of one-dimensional nanomaterials whose performance depends on the anisotropic crystal properties.