Nanoimaging of localized plasmon-induced charge separation

Distribution of the plasmon-induced charge separation sites at the Ag nanorod-TiO(2) interface is visualized by AFM. The charge separation sites are localized in almost the same way as electric fields around the nanorods, indicating that the charge separation is induced or promoted by the localized electric fields.     

Model companions of theories of graphs

We study model companions of theories extending the graph axioms. First we prove general results concerning the existence of the model companion. Then, by applying these results to the case of graphs, we give a series of companionable and non‐companionable examples.     

Enhancing the effect of the nanofiber network structure on thermoresponsive wettability switching

This letter reports the enhancing effects of a nanofiber network structure on stimuli-responsive wettability switching. Thermoresponsive coatings composed of nanofibers were prepared by electrospinning from thermoresponsive polymer poly(N-isopropylacrylamide) (PNIPAAm). The nanofiber coatings showed a large amplitude of thermoresponsive change in the wettability from hydrophilic to hydrophobic states compared to a smooth cast film. In particular, the combination of the surface chemistry and unique topology of the electrospun nanofiber coatings enables a transition from the Wenzel state to the metastable Cassie-Baxter state with an increase in temperature and consequently an enhanced amplitude of change in the water contact angles: the apparent contact angle differences between 25 and 50 °C are Δθ*(25-50?°C?)= 108 and 10° for the nanofiber coatings with a diameter of 830 nm and a smooth cast film, respectively. The fabrication of the 3D nanofiber network structure by electrospinning from stimuli-responsive materials is a promising option for highly responsive surfaces in wettability.     

Basic structure and cell culture condition of a bioartificial renal tubule on chip towards a cell-based separation microdevice

Various separation processes have been integrated in microfluidics, such as capillary electrophoresis and chromatography, on a microchip. However, it is extremely difficult to separate a complicated biological system by conventional methods. Here, we report on a feasible structure and the culture condition of human renal proximal tubule epithelial cells (RPTECs), with the aim to construct a bioartificial renal tubule on a chip. Glass microchips and a polycarbonate membrane were sealed with no leakage after a surface modification. Furthermore, matrigel was selected as an optimized extracellular matrix (ECM) for cell-proliferation on the membrane. After culturing for 5 days, RPTECs reached confluent in the chip-membrane structure, which was confirmed by nuclei staining. So far, we have constructed the basic structure and cell proliferation circumstance for the future demonstration of the RPTECs separating function. This separation microdevice has promising potential to be applied as both a unit of a circulation cell culture system and a research platform of cell biology.     

Syntheses of all-methylated ellagitannin, isorugosin B and rugosin B

Ellagitannins possess a wide range of biological activities and remarkable structural diversity, which commonly include an axially chiral biaryl unit. This paper describes syntheses of all-methylated versions of isorugosin B and rugosin B, which are regioisomeric, ellagitannin-related compounds. The key features of these syntheses involve the construction of an axially chiral biaryl function on a sugar moiety through a Pd-catalyzed intramolecular biaryl coupling reaction, Bringmann’s atroposelective lactone opening reaction, and a two-step ester formation. This is the first synthetic approach for generating ellagitannins featuring a valoneoyl group.     

Design and characterization of endosomal-pH-responsive coiled coils for constructing an artificial membrane fusion system

A weakly acidic pH-responsive polypeptide is believed to have the potential for an endosome escape function in a polypeptide-triggered delivery system. For constructing a membrane fusion device with pH-responsiveness, we have designed novel polypeptides that are capable of forming an α2 coiled coil structure. Circular dichroism spectroscopy reveals that a polypeptide, AP-LZ(EH5), with a Glu and His salt-bridge pair at a staggered position in the hydrophobic core forms a stable coiled coil structure only at endosomal pH values (pH 5.0 to 5.5). On the basis of their endosomal-pH responsiveness, a boronic acid/polypeptide conjugate (BA-H5-St) was also designed as a pilot molecule to construct a pH-responsive, one-way membrane fusion system with a sugarlike compound (phosphatidylinositol: PI)-containing liposome as a target. Membrane fusion behavior was characterized by lipid-mixing, inner-leaflet lipid-mixing, and contents-mixing assays. These studies reveal that membrane fusion is clearly observed when the pH of the experimental system is changed from 7.4 (physiological condition) to 5.0 (endosomal condition).     

Temperature effect on emission spectra and fluorescence lifetime of the ~4I_(13/2) state of Er~(3+)-doped Gd_2SiO_5 crystal

By measuring the emission spectra and the fluorescence lifetime of the 4 I 13 /2 state of Er 3+ ions in Gd 2 SiO 5 crystal at different temperatures,the effects of temperature on the spectra and the lifetime of the 4 I 13 /2 state are investigated. When the temperature increases,the emission line width for the 4 I 13 /2 → 4 I 15 /2 transition is broadened,and the main emission lines at 1 596,1 609,and 1 644 nm shifte toward shorter wavelengths. The measured lifetime of the 4 I 13 /2 state decreases from 13.2 to 8.4 ms with temperature increase from 13 to 300 K,which is mainly due to the temperature dependence of multiphonon relaxation between the 4 I 13 /2 and 4 I 15 /2 states and the changing population distribution among the Stark levels within the 4 I 13 /2 state. The experimental results imply that low temperature condition is better for the ～1.6-μm laser output.     

Raman microscopy of a small uniaxial crystal: Tetragonal aspartame

A general method is presented for determining the shape and orientation of the Raman tensor of a molecule in a uniaxial crystal using a Raman microscope. First, equations are derived to connect the Raman tensor components (α_xx, α_yy, etc.) of a molecule to the Raman tensor components (α_aa, α_cc, etc.) of a crystal that is composed of molecules in a uniaxial arrangement, with an orientation specified by the two angles χ and θ. Next, a method is presented to obtain a correct set of values of the intensity ratios I_ac/I_aa and I_cc/I_aa from observed values of the intensity ratios measured with a Raman microscope. To augment the experimental data, the depolarization ratio ρ (for a completely random molecular orientation) is plotted as a function of r₁ = α_xx/α_zz and r₂ = α_yy/α_zz, so that a possible set of r₁ and r₂ values can be found from an observed value of ρ. The method has been applied to an aspartame IIA crystal (P4₁). A set of values of r₁, r₂, χ and θ has been determined for each of the following Raman fundamentals: 1741 cm⁻¹ (ester CO stretch), 1667 cm⁻¹ (amide I), 1275 cm⁻¹ (amide III) and 1204 cm⁻¹ (C C_phenyl stretch), excited at 488.0 nm.