Constituents of the quasiparticle spectrum along the nodal direction of high-Tc cuprates

Applying the Kramers-Kronig consistent procedure, developed earlier, we investigate in detail the formation of the quasiparticle spectrum along the nodal direction of high-Tc cuprates. The heavily discussed "70 meV kink" on the renormalized dispersion exhibits a strong temperature and doping dependence when purified from structural effects such as bilayer splitting, diffraction replicas, etc. This dependence is well understood in terms of fermionic and bosonic constituents of the self-energy. The latter follows the evolution of the spin-fluctuation spectrum, emerging below some doping dependent temperature and sharpening below Tc, and is mainly responsible for the formation of the kink in question.     

Novel 3D coordination palladium-network complex: a recyclable catalyst for Suzuki-Miyaura reaction

A novel solid-phase 3D metal-organic coordination network catalyst was prepared via self-assembly from PdCl2(CH3CN)2 and a trisphosphine hub with three flexible alkyl-chain linkers. This insoluble network complex efficiently catalyzed the Suzuki-Miyaura reaction under atmospheric conditions in water. This catalyst was reused without loss of catalytic activity.     

Asteropine A, a sialidase-inhibiting conotoxin-like peptide from the marine sponge Asteropus simplex

Marine sponges contain structurally intriguing and biologically active peptides of nonribosomal peptide synthase origin, often containing amino acids with novel structures. Here we report the discovery of asteropine A (APA), a cystine knot to be isolated from marine sponges. The solution structure of APA as determined by NMR belongs to the four-loop class of cystine knots similar to those of some conotoxins and spider toxins. However, the highly negatively charged surface of APA is uncommon among other cystine knots. APA competitively inhibits bacterial sialidases, but not a viral sialidase. APA was inactive against all other enzymes tested and did not have any apparent antitumor activity. Our data suggest that APA and other knotting peptides may be important leads for antibacterial and even antiviral drug development.     

Three-phase solvent systems for comprehensive separation of a wide variety of compounds by high-speed counter-current chromatography

Three-phase solvent systems were efficiently utilized for high-speed counter-current chromatography (HSCCC) to separate multiple components with a wide range of hydrophobicity. The compositions of three-phase systems were optimized according to their physical parameters such as volume ratio, viscosity and specific gravity of upper (UP), middle (MP) and lower (LP) phases. The three-phase systems composed of n-hexane-methyl acetate-acetonitrile-water (4:4:3:4, v/v/v/v) was selected for HSCCC separation of a mixture of 15 standard compounds with a wide range in hydrophobicity from beta-carotene to tryptophan. The separation was initiated by filling the column with a mixture of MP and LP both as a stationary phase followed by elution with UP to separate the hydrophobic compounds. Then the mobile phase was switched to MP to elute the moderately hydrophobic compounds, and finally the polar compounds still retained in the column were fractionated by eluting the column with LP. The system successfully resolved all 15 compounds in one-step operation in 70 min.     

Effect of the cell type and cell density on the binding of living cells to a silica particle: an atomic force microscope study

We used the atomic force microscope to study how the cell type and the density of cells adsorbed at a substrate can affect the adhesion between a living cell and a model drug delivery system (DDS) carrier nano-particle. We used three different anchorage-dependent cells, i.e., a living mouse fibroblast cell (L929), a living human colon cancer cell (Caco2), and a living mouse malignant melanoma cell (B16F10). For the DDS model nano-particle, we used a silica colloid. In order to correlate the adhesion force with the cell types, the growth curve of the cells were determined with a haemocytometer. The shapes of the cells at the different stages were monitored by light microscopy, and the morphology of their surfaces obtained by tapping mode atomic force microscopy.

Force measurements showed that the Caco2 cell bound little to a silica particle, regardless of the cell density. The L929 cell bound well to a silica particle for low and high cell densities. The B16F10 cell bound little to a silica particle for low cell densities, but bound well for high cell densities. AFM images showed that the L929 cell did not contain folds. The B16F10 cells, however, displayed folds in the cell surface for low cell densities, but no folds in the cell for high cell densities. As literature also reported that the Caco2 cell contains folds, these results suggested that cells with folds showed less adhesion to a silica particle than cells without folds. The presence of folds in the cell presumably decreased the number of sites on the cell that could hydrogen bond or undergo van der Waals binding with the silanol groups of the silica particle.     

Iron-based layered superconductor: LaOFeP

We report superconductivity in an iron-based layered oxy-pnictide LaOFeP. LaOFeP is composed of an alternate stack of lanthanum oxide (La3+O2-) and iron pnictide (Fe2+P3-) layers. Magnetic and electrical resistivity measurements verify the occurrence of the superconducting transition at approximately 4 K.     

Large dielectric susceptibility associated with proton transfer in a supramolecular structure of chloranilic acid and 5,5'-dimethyl-2,2'-bipyridine

A 1:1 adduct of chloranilic acid with 5,5'-dimethyl-2,2'-bipyridine, in which two kinds of molecules are connected by infinite hydrogen bond chains, exhibits a distinct dielectric phase transition when cooled. Below T(c)(=318 K) the hydrogen atoms participating in hydrogen bonding undergo long-range ordering and form an antiferroelectric-like state, taking a single minimum potential in the high-temperature phase (T>T(c)) due to the bifurcate hydrogen bond system. The proton-transfer phenomenon was clearly observed by electron density distribution analysis using a maximum entropy method of synchrotron x-ray diffraction data.     

Syntheses of armed‐macrocycles by reductive amination using NaBH(OAc)3 under 1 MPa

Armed‐monoaza‐12‐crown‐4, monoaza‐15‐crown‐5, diaza‐12‐crown‐4, diaza‐18‐crown‐6 ethers, and 1,4,7,10‐tetraazacyclododecane having aromatic pendants were prepared by the reductive amination of the corresponding macrocycles with aromatic carboxyaldehydes in the presence of NaBH(OAc)₃. Reductive amination under 1 MPa conditions provided significant shortening of the reaction time and yield enhancements.     

Functional cDNA expression cloning: pushing it to the limit

The 1970s and the following decade are the era of the birth and early development of recombinant DNA technologies, which have entirely revolutionized the modern life science by providing tools that enable us to know the structures of genes and genomes and to dissect their components and understand their functions at the molecular and submolecular levels. One major objective of the life sciences is to achieve molecular and chemical understandings of the functions of genes and their encoded proteins, which are responsible for the manifestation of all biological phenomena in organisms. In the early 1980s, I developed, together with Paul Berg, a new technique that enables the cloning of full-length complementary DNAs (cDNAs) on the basis of their functional expression in a given cell of interest. I review the development, application and future implications in the life sciences of this gene-cloning technique.