Design of a stabilized short helical peptide and its application to catalytic enantioselective epoxidation of (E)-chalcone

Stabilized short helical heptapeptides containing a combination of an α-aminoisobutyric acid as a helical promoter and l/d-serine derivatives to produce cross-linked units were synthesized. The cyclic peptide R₃,₇R-2, which had d-serine derivatives at its 3rd and 7th positions, formed a stable right-handed (P) α-helix in solution and the crystalline state. Furthermore, its N-terminal free helical peptide catalyzed the enantioselective epoxidation of (E)-chalcone to afford the epoxide in a high yield and moderate enantioselectivity.     

Orange and yellow crystals of copper(I) complexes bearing 8-(diphenylphosphino)quinoline: a pair of distortion isomers of an intrinsic tetrahedral complex

The tetrafluoroborate salt of bis{8-(diphenylphosphino)quinoline}copper(I), [Cu(Ph(2)Pqn)(2)]BF(4), afforded orange prismatic (2O) or yellow columnar (2Y) crystals, dependent on the solvent and concentration of the recrystallization solution used. X-ray analysis revealed that crystals of 2O and 2Y had the same composition and exhibited different crystal systems: 2O was triclinic, with space group P ?1 and Z = 2, and 2Y was monoclinic with space group P2(1)/c and Z = 4. In these crystals, the tetrahedral copper(I) complex exhibited a strong "rocking distortion" toward a trigonal pyramidal coordination geometry (by a slide translation of one of the unsymmetrical bidentate chelating ligands along the tetrahedral edge). In addition, both the 2O and 2Y complexes showed a "flattening distortion", meaning that the dihedral angle between the two chelate planes were off-perpendicular and oriented toward opposite directions, which resulted in a pair of distortion isomers: syn clinal (sc: 2O) and anti clinal (ac: 2Y). (31)P CP-MAS NMR spectroscopy indicated that 2O and 2Y could be distinguished. Both isomers exhibited inequivalent P atoms, but a larger difference in chemical shift was observed in 2Y. TD-DFT calculations reproduced the difference in spectra between the orange- and yellow-colored complexes, which originated from metal-to-ligand charge-transfer transitions.     

Pt nanoworms: creation of a bumpy surface on one-dimensional (1D) Pt nanowires with the assistance of surfactants embedded in mesochannels

A new type of platinum nanowire with a bumpy surface "Pt nanoworm" is electrochemically synthesized in mesochannels of mesoporous silica films with the assistance of a nonionic surfactant (C(16)EO(8)).     

Bound H dibaryon in flavor SU(3) limit of lattice QCD

The flavor-singlet H dibaryon, which has strangeness -2 and baryon number 2, is studied by the approach recently developed for the baryon-baryon interactions in lattice QCD. The flavor-singlet central potential is derived from the spatial and imaginary-time dependence of the Nambu-Bethe-Salpeter wave function measured in N(f)=3 full QCD simulations with the lattice size of L?2,3,4 fm. The potential is found to be insensitive to the volume, and it leads to a bound H dibaryon with the binding energy of 30-40 MeV for the pseudoscalar meson mass of 673-1015 MeV.     

Solid-phase combinatorial syntheses of mesomorphic 4-alkoxyphenyl 4-alkoxybenzoylaminobenzoates

Eighteen two-ring and 100 three-ring benzenoid amides were synthesised using a solid-phase combinatorial method involving acylation or benzoylation and palladium(0)-catalysed carbonylation of a secondary amine, obtained by the reductive amination of 4-iodoaniline and a backbone amide linker. The purity of the products obtained was high enough for investigation of their thermal properties. All the three-ring derivatives were shown to be mesomorphic, but the two-ring derivatives were not. The mesomorphic behaviour and the transition temperatures of the three-ring derivatives were virtually identical to those of samples obtained by liquid-phase synthesis and purified by column chromatography and recrystallisation.     

Hereditary Spastic Paraplegia Protein Spartin Is an FK506-Binding Protein Identified by mRNA Display

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Conformational studies on peptides having chiral five-membered ring amino acid with two azido or triazole functional groups within the sequence of Aib residues

The chiral cyclic α,α-disubstituted α-amino acid, (3R,4R)-1-amino-3,4-diazido-1-cyclopentanecarboxylic acid [(R,R)-Ac₅c^dN3], was introduced into achiral α-aminoisobutyric acid (Aib) peptides. The azido groups of (R,R)-Ac₅c^dN3 in the peptides were efficiently converted into 1,2,3-triazole functional groups. FTIR, ¹H NMR, and CD spectra revealed that the dominant conformations of all peptides in solution were 3₁₀-helical structures without controlling the helical-screw sense. X-ray crystallographic analyses of peptides containing (R,R)-Ac₅c^dN3 showed that both the right-handed (P) and left-handed (M) 3₁₀-helical structures were present in the crystal state.     

Pyrene-zipper array assembled via RNA duplex formation

We describe a new strategy for multipyrene modification of RNA sequences to form unique structures of pyrene aromatic arrays, the "pyrene-zipper array", on duplex RNA that exhibits remarkably strong excimer fluorescence.     

Hydrodynamic control of droplet division in bifurcating microchannel and its application to particle synthesis

We describe herein a microfluidic system for active and precise control of droplet division at a bifurcation point in a microchannel. Water-in-oil or oil-in-water droplets, which were initially formed at a T-junction, were introduced into the bifurcation point, and then divided into two daughter droplets. By continuously introducing 'tuning flow' into the downstream of one of the branch channels, and by controlling the flow rates distributed into the two branch channels, the sizes of the daughter droplets could be precisely tuned. The ratio of the volumetric flow rates into the branch channels was estimated by regarding the microchannel network as a resistive circuit. In addition, we performed synthesis of monodispersed polymer particles with controlled sizes utilizing the presented system. The ability to hydrodynamically control the droplet sizes will open new possibilities not only for producing useful emulsions, but also for conducting controlled chemical and biochemical reactions in a confined space.