A Rational Repeating Template Method for Synthesis of 2 D Hexagonally Ordered Mesoporous Precious Metals

A repeating template method is presented for the synthesis of mesoporous metals with 2D hexagonal mesostructures. First, a silica replica (i.e., silica nanorods arranged periodically) is prepared by using 2D hexagonally ordered mesoporous carbon as the template. After that, the obtained silica replica is used as the second template for the preparation of mesoporous ruthenium. After the ruthenium species are introduced into the silica replica, the ruthenium species are then reduced by a vapor‐infiltration method by using the reducing agent dimethylamine borane. After the ruthenium deposition, the silica is chemically removed. Analysis by transmission and scanning electron microscopies, a nitrogen‐adsorption–desorption isotherm, and small‐angle X‐ray scattering revealed that the mesoporous ruthenium had a 2D hexagonal mesostructure, although the mesostructural ordering is decreased compared to that of the original mesoporous carbon template. This method is widely applicable to other metal systems. By changing the metal species introduced into the silica replica, several mesoporous metals (palladium and platinum) can be synthesized. Ordered mesoporous ruthenium and palladium, which are not easily attainable by the soft‐templating methods, can be prepared. This study has overcome the composition variation limitations of the soft‐templating method.     

A general strategy to determine a target DNA sequence of a short peptide: application to a d-peptide.

Short peptides could potentially provide a novel element to read-out DNA sequences from the major groove. However, it is difficult to determine sequence-preference of de novo designed monomeric short peptides. Because DNS-binding affinity and specificity of short peptides are usually much lower than those of native DNA-binding proteins, determining the sequence-preference of short peptides by conventional methods utilized to deduce the target sequence of proteins often produces an unclear outcome. We report here a general strategy to defining the sequence-preference of a DNA-binding short peptide by using the heterodimers. A GCN4 basic region peptide tethers a low-affinity DNA-binding peptide adjacent to a GCN4 binding sequence through the cyclodextrin-adamantane association, thereby increasing local concentration of the low-affinity peptide on degenerated DNA sequences. An increase of the local concentration allows one to select a preferential sequence for the low-affinity DNA binding peptide. The method successfully identified specific sequences of short peptides derived from native DNA-binding proteins. The usefulness of this approach has been demonstrated by identifying preferred DNA targets for a peptide composed only of d-amino acids. The method is potentially applicable not only to artificial peptides, but also to other synthethic ligands.     

1,4-silatropy of S-alpha-silylbenzyl thioesters: a convenient route to silyl enol and dienol ethers accompanied by C-C bond formation via thiocarbonyl ylides

A novel convenient method for the generation of thiocarbonyl ylides from readily accessible starting materials and the first synthetic application of in situ generated ylides in the synthesis of silyl enol and dienol ethers, accompanied by C-C bond formation, is described. Under completely neutral conditions without any catalyst or additive, thermal reactions of S-alpha-silylbenzyl thioesters in sealed tubes at 180 degrees C provided silyl enol and dienol ethers in good to excellent yields with high stereoselectivities. This procedure consists of a multistep reaction in a one-pot process, i.e., 1,4-silatropy of S-alpha-silylbenzyl thioesters to give thiocarbonyl ylides, 1,3-electrocyclization of the ylides to give thiiranes, and the extrusion of sulfur from thiiranes to give silyl enol and dienol ethers.     

Structures and colour properties of new red wine pigments

Two new red pigments were synthesized by nucleophilic addition of vinylphenols to malvidin 3-glucoside. The structures of the resulting pyranoanthocyanins were confirmed by electrospray-mass spectrometry and NMR spectroscopy (gHMQC, gHMBC and CIGAR experiments). By means of UV-vis spectroscopy the colour properties of the pigments were characterized; it could be demonstrated that the pyranoanthocyanins retained their red colour at pH 3.6 in model wine and were resistant to bisulfite-mediated bleaching. Finally, HPLC-MS analysis confirmed the presence of both anthocyanin-derived pigments in red wine.     

Morphological phase behaviour under pressure of polycatenar mesogens with a perfluorinated moiety

Two polycatenar materials composed of a four‐aromatic‐ring core with a perfluorinated moiety attached in one terminal position through either butylene‐ or pentylene spacer groups, and three tetradecyloxy chains at the other end (abbreviated as 14PC₄F and 14PC₅F), were investigated to study the effect of pressure on the phase transition behaviour. A polarizing optical microscope equipped with a high pressure optical hot stage, was used for the purpose. The T vs. P phase diagrams of 14PC₄F and 14PC₅F were constructed in the pressure region up to 100 MPa. 14PC₄F showed the stable crystal (Cr₁)–columnar tetragonal (Col_tet)–smectic A (SmA)–columnar hexagonal (Col_h)–isoropic liquid (I) phase transition sequence under all pressures. 14PC₅F exhibited the phase sequence metastable crystal (Cr₂)–cubic (Cub)–Col_tet–SmA–I in a melt‐cooled sample on heating under pressure. But when the melt‐cooled Cr₂ sample was annealed at 52–54°C for 2–3 h, the stable crystal (Cr₁) was formed slowly, giving a stable Cr₁–Cub–Col_tet–SmA–I phase sequence. The temperature region of the stable cubic phase broadened with increasing pressure. Furthermore a new mesophase of 14PC₅F was pressure‐induced between the I and SmA phases on cooling at pressures above about 16 MPa. Since the monotropic mesophase exhibited a texture very similar to that of the high temperature Col_h phase of 14PC₄F with planar orientation, the new phase was assigned at a high temperature columnar hexagonal phase of 14PC₅F.     

Effect of Increasing Concentration of Each of Three Polar Solvents (1,4-Dioxane, Dimethyl Sulfoxide, N,N-Dimethylformamide) on Changes in the Shape of Polysorbate 20 Micelles

The effect of increasing concentration of each of three polar solvents [0–40 % (v/v) 1,4-dioxane, 0–40 % (v/v) dimethyl sulfoxide (DMSO), and 0–60 % (v/v) N,N-dimethylformamide (DMF)] on changes in the shape of the surfactant polysorbate 20 (Tween 20) micelles in the aqueous, polar solvent, sodium phosphate buffer solutions (pH = 7.2, ionic strength 2.44 mmol·L^?1) were investigated by using small-angle X-ray scattering. The effect of increasing concentration of 1,4-dioxane is that the micelle shape changed from core–shell cylindrical micelles to core–shell disc micelles between concentrations of 10 and 20 % (v/v) 1,4-dioxane, and then from core–shell disc micelles to core–shell elliptic disc micelles between concentrations of 30 and 40 % (v/v) 1,4-dioxane. The effect of increasing concentration of DMSO is that the micelles changed from core–shell cylindrical micelles to core–shell disc micelles between concentrations of 0 and 10 % (v/v) DMSO. The effect of increasing concentration of DMF is that it changed the core–shell cylindrical micelles to core–shell disc micelles between concentrations of 30 and 40 % (v/v) DMF. The common effect is that the solvents shortened the height of the micelle, that is, they squashed the micelle. Moreover, the specific effect of 1,4-dioxane is that this solvent squashed and squeezed the micelle.     

Properties of hollow bent output tips in CO2 laser light delivery system

In order to change the output direction of laser light in a small operation space, two types of hollow bent output tips are proposed for medical laser light delivery system. One is the hollow fiber insert-type, which is of the minimum bending radius of 3 cm. The other type, based on a fixed-bent pyrex glass tube, is of the minimum bending radius of 2 mm. Both types of tips are inner-coated with a silver layer and a cyclic olefin polymer (COP) layer. Loss properties for CO₂ laser light are clarified for the insert-type tips with various bending angles and radii. For the fixed-bent tips, the losses are around 0.7 dB, which are almost not dependent on the bending angles and radii. Transmissions of the tips remain undamaged after 1-h-delivery of 5 W output CO₂ laser light. A nickel layer is coated on the outside wall of fixed-bent tips so as to increase the mechanical strength and lower the surface temperature. Characteristics of surface temperature distribution and time response were experimentally discussed. Transmission properties of pilot beams are also evaluated.     

Fluorescent supramolecular polymers of barbiturate dyes with thiophene-cored twisted π-systems

Because supramolecular polymerization of emissive π-conjugated molecules depends strongly on π–π stacking interaction, the formation of well-defined one-dimensional nanostructures often results in a decrease or only a small increase of emission efficiency. This is also true for our barbiturate-based supramolecular polymers wherein hydrogen-bonded rosettes of barbiturates stack quasi-one-dimensionally through π–π stacking interaction. Herein we report supramolecular polymerization-induced emission of two regioisomeric 2,3-diphenylthiophene derivatives functionalized with barbituric acid and tri(dodecyloxy)benzyl wedge units. In CHCl₃, both compounds are molecularly dissolved and accordingly poorly emissive due to a torsion-induced non-radiative decay. In methylcyclohexane-rich conditions, these barbiturates self-assemble to form crystalline nanofibers and exhibit strongly enhanced emission through supramolecular polymerization driven by hydrogen-bonding. Our structural analysis suggests that the barbiturates form a tape-like hydrogen-bonding motif, which is rationalized by considering that the twisted geometries of 2,3-diphenylthiophene cores prevend the competing rosettes from stacking into columnar supramolecular polymers. We also found that a small difference in the molecular polarity originating from the substitutional position of the thiophene core influences interchain association of the supramolecular polymers, affording different luminescent soft materials, gel and nanosheet.

Two barbiturate dyes with regioisomeric thiophene-cored twisted π-systems show strongly enhanced emission through supramolecular polymerization. The supramolecular polymers thus formed exhibit distinct emission colors and degree of agglomeration.