Water irradiation by high-frequency ultrasonic wave: effects on properties of passive film formed on stainless steel

In this paper an aqueous solution was irradiated with a 1.63MHz ultrasonic wave. It is shown that if stainless steel can passivate under dynamic polarization in this medium, under static polarization, the latter does not show any repassivation behaviour with time. This is attributed to a diminution of the diffusion layer thickness that is developed at the electrode/electrolyte interface, which is associated with a production of H(2) species by sonolysis and which maintains reductive conditions at the interface. The oxide film formed under ultrasonic irradiation for 1h at a passive potential of+0.2V(SCE) shows an early stage of passivation and an increased disordered state, which implies a considerable decrease in the corrosion resistance behaviour of the sample. The polarization resistance of the stainless steel R(p) is divided by a value of 4.5 under ultrasonic conditions.     

Rapid detection of a cocaine-binding aptamer using biological nanopores on a chip

This paper describes a methodology for the rapid and highly selective detection of cocaine using a membrane protein channel combined with a DNA aptamer. The DNA aptamer recognizes the cocaine molecule with high selectivity. We successfully detected a low concentration of cocaine (300 ng/mL, the drug test cutoff limit) within 60 s using a biological nanopore embedded in a microchip.     

Linear- and angular-shaped naphthodithiophenes: selective synthesis, properties, and application to organic field-effect transistors

A straightforward synthetic approach that exploits linear- and angular-shaped naphthodithiophenes (NDTs) being potential as new core structures for organic semiconductors is described. The newly established synthetic procedure involves two important steps; one is the chemoselective Sonogashira coupling reaction on the trifluoromethanesulfonyloxy site over the bromine site enabling selective formation of o-bromoethynylbenzene substructures on the naphthalene core, and the other is a facile ring closing reaction of fused-thiophene rings from the o-bromoethynylbenzene substructures. As a result, three isomeric NDTs, naphtho[2,3-b:6,7-b']dithiophene, naphtho[2,3-b:7,6-b']dithiophenes, and naphtho[2,1-b:6,5-b']dithiophene, are selectively synthesized. Electrochemical and optical measurements of the parent NDTs indicated that the shape of the molecules plays an important role in determining the electronic structure of the compounds; the linear-shaped NDTs formally isoelectronic with naphthacene have lower oxidation potentials and more red-shifted absorption bands than those of the angular-shaped NDTs isoelectronic with chrysene. On the contrary, the performance of the thin-film-based field-effect transistors (FETs) using the dioctyl or diphenyl derivatives were much influenced by the symmetry of the molecules; centrosymmetric derivatives tend to give higher mobility (up to 1.5 cm(2) V(-1) s(-1)) than axisymmetric ones (～0.06 cm(2) V(-1) s(-1)), implying that the intermolecular orbital overlap in the solid state is influenced by the symmetry of the molecules. These results indicate that the present NDT cores, in particular the linear-shaped, centrosymmetric naphtho[2,3-b:6,7-b']dithiophene, are promising building blocks for the development of organic semiconducting materials.     

Dianthra[2,3-b:2',3'-f]thieno[3,2-b]thiophene (DATT): synthesis, characterization, and FET characteristics of new π-extended heteroarene with eight fused aromatic rings

A novel highly π-extended heteroarene with eight fused aromatic rings, dianthra[2,3-b:2',3'-f]thieno[3,2-b]thiophene (DATT), was selectively synthesized via a newly developed synthetic strategy, fully characterized by means of single crystal X-ray structural analysis, and examined as an organic semiconductor in thin film transistors. Even with its highly extended acene-like π-system, DATT is a fairly air-stable compound with IP of 5.1 eV. Single crystal X-ray structural analysis revealed its planar molecular structure and the lamella-like layered structure with typical herringbone packing. Theoretical calculations of the solid state electronic structure based on the bulk single crystal structure suggest that DATT affords almost comparable intermolecular orbital couplings between HOMOs (t(HOMO)) with those of dinaphtho[2,3-b:2',3'-f]thieno[3,2-b]thiophene (DNTT), implying its good potential as an organic semiconductor for organic field-effect transistors. In fact, field-effect mobilities as high as 3.0 cm(2) V(-1) s(-1) were achieved with vapor-processed DATT-based devices, which is comparable with that of DNTT-based devices. The molecular ordering of DATT in the thin film state, however, turned out to be not completely uniform; as elucidated by in-plane and out-of-plane XRD measurements, the face-on molecular orientation was contaminated in the edge-on orientation, the former of which is not optimal for efficient carrier transport and thus could limit the mobility.     

Syntheses and luminescent properties of 3,5-diphenylpyrazolato-bridged heteropolynuclear platinum complexes. The influence of chloride ligands on the emission energy revealed by the systematic replacement of chloride ligands by 3,5-dimethylpyrazolate

Heteropolynuclear Pt(II) complexes with 3,5-diphenylpyrazolate [Pt(2)Ag(4)(μ-Cl)(2)(μ-Ph(2)pz)(6)] (3), [Pt(2)Ag(2)Cl(2)(μ-Ph(2)pz)(4)(Ph(2)pzH)(2)] (4), [Pt(2)Cu(2)Cl(2)(μ-Ph(2)pz)(4)(Ph(2)pzH)(2)] (5), [Pt(2)Ag(4)(μ-Cl)(μ-Me(2)pz)(μ-Ph(2)pz)(6)] (7), and [Pt(2)Ag(4)(μ-Me(2)pz)(2)(μ-Ph(2)pz)(6)] (8) have been prepared and structurally characterized. These complexes are luminescent except for 5 in the solid state at an ambient temperature with emissions of red-orange (3), orange (4), yellow-orange (7), and green (8) light, respectively. Systematic red shift of the emission energies with the number of chloride ligands was observed for 3, 7, and 8. DFT calculations indicate that the highest occupied molecular orbital (HOMO) as well as HOMO-1 of the heterohexanuclear complexes, 3, 7, and 8, having Pt(2)Ag(4) core, mainly consist of dδ orbital of Pt(II) and π orbitals of Ph(2)pz ligands, while the lowest unoccupied molecular orbital (LUMO) of these complexes mainly consists of in-phase combination of 6p of two Pt(II) centers and 5p of four Ag(I) centers. It is likely that the emissions of 3, 7, and 8 are attributed to emissive states derived from the Pt(2)(d)/π → Pt(2)Ag(4) transitions, the emission energy of which depends on the ratio of chloride ligands to pyrazolate ligands.     

First synthesis of 1-(indol-2-yl)azulenes by the Vilsmeier–Haack type arylation with triflic anhydride as an activating reagent

Azulene derivatives reacted with 2-indolinones in the presence of triflic anhydride (Tf₂O) to afford 1-(indol-2-yl)azulenes in good yields. In the cases of the reaction of 6-tert-butyl-1-(methylthio)azulene (11) and 1-(1,4-dihydropyridin-4-yl)azulene 14, 1,1′-biazulene derivative 24 and 1-(indol-2-yl)azulene (2) were obtained under the similar reaction conditions, respectively, instead of the presumed electrophilic substitution products.     

Concise and highly stereoselective synthesis of the C20-C26 building block of halichondrins and Eribulin

A concise, stereoselective, and scalable synthesis of the C20-C26 building block of halichondrins and Eribulin is reported. The synthesis relies on three key transformations: regiospecific Ru-catalyzed intramolecular hydrosilylation, highly stereoselective S(N)2' substitution, and selective conversion of a C-Si to C-I bond. It is carried out in a 5-pot/4-workup operation without chromatographic purification, except for filtration through a silica-gel plug, to give the C20-C26 building block (dr > 200:1; ee > 99%) in ca. 60% overall yield from epoxide 1.     

Air-stable heterobimetallic catalysts to effect Ni/Cr-mediated couplings with a ca. 1:1 molar ratio of coupling partners at low catalyst loadings

Two air-stable Ni,Cr-heterobimetallic catalysts have been prepared from ligands 7 and 11, obtained from scyllo-inositol in four and three steps, respectively. Both catalysts smoothly promote Ni/Cr-mediated coupling reactions with a ca. 1:1 molar ratio of coupling partners. The catalyst derived from 11 exhibits a better catalytic profile, thereby allowing Ni/Cr-mediated coupling reactions to be achieved with a wide range of substrates at a low catalyst loading in an operationally simple manner.     

Enzymatic Reaction in Droplets Manipulated with Liquid Dielectrophoresis

Droplet generation and transportation for biological reactions are conducted with liquid dielectrophoresis (LDEP), forming two hundred picoliter droplets and aligning them in an open environment above the micro‐machined electrodes. The generation of the dielectrophoresis signals was critically examined to actuate droplets in biological solutions without excessive Joule heating. Enzymatic reactions between β‐galactosidase and fluorescein di‐β‐D ‐galactopyranoside were succeeded in manipulated droplets, which was confirmed by fluorescence imaging. These results allow us to propose the integration of LDEP actuation in high throughput biomolecular assays.     

Enhanced bile canaliculi formation enabling direct recovery of biliary metabolites of hepatocytes in 3D collagen gel microcavities

Analysis of biliary metabolites is essential to predict pharmacokinetics and hepatotoxicity during drug development. In this paper, we present a hepatocyte culture configuration that enables the direct recovery of bile acid that accumulates in bile canaliculi by embedding the hepatocytes in a 3D micropatterned collagen gel substrate. We investigated the formation of bile canaliculi in hepatocytes embedded in circular microcavities of various sizes and made from collagen gel. Image analyses using fluorescently labeled bile acid revealed that the area of bile canaliculi in embedded hepatocytes in a microcavity of 60 or 80 μm in diameter was enlarged when compared with other sized microcavities and those of hepatocytes cultured using conventional hepatocyte sandwich cultures. We successfully recovered bile acid from the enlarged bile canaliculi of hepatocytes cultured in microcavities using a glass capillary and quantified the amount recovered. Using our approach, the direct recovery of biliary metabolites, using hepatocyte cultures with enhanced biliary excretion and geometrically enlarged bile canaliculi, may enable accurate screening of pharmacokinetics and drug-drug interactions against drug transporters.