Anisotropic paramagnetic shift of μ−O in the highT c related materials LaSrCuO and LaCuO

The negative muon (^–) was used as a microscopic probe for the study of the electronic state at the oxygen site in highT _c related LaSrCuO materials. Using good single crystals, two types of signals are obtained corresponding to two different oxygen sites: one highly anisotropic, which shows a large (order of 1%) shift under the magnetic field inc-axis direction, the other less anisotropic and with a smaller amplitude (order of 0.2%). These results of ^–OSR show quit a difference with the result of¹⁷O-NMR, where the paramagnetic shift has axial symmetry along the Cu-O bond direction and a magnitude of the order of 0.2% and 0.05%.     

EXAFS/FT-IR characterization of tetra-iridium carbonyl clusters bound to tris-(hydroxymethyl)phosphine grafted silica surface catalytically active for propene oxidation to acetone

Structure and catalytic activity of Ir₄(CO)₁₂ bound to tris-(hydroxymethyl)phosphine (THP) grafted silica (THP/SiO₂) was investigated by means of EXAFS, FT-IR and kinetic studies. It was found that Ir₄(CO)₁₂ was uniformly attached on THP/SiO₂ by substitution of CO by THP (Ir₄/THP/SiO₂). The tetra-iridium carbonyl cluster framework was remained during the substitution of THP ligands and two THP ligands coordinated to the iridium carbonyl clusters to form Ir₄(CO)₁₀(THP/SiO₂)₂. species. When Ir₄/THP/SiO₂ was evacuated at 373 K, bridge CO was desorbed and Debye-Waller factor of Ir---Ir contribution derived from EXAFS analysis was increased which suggested that the cluster framework was distorted by the evacuation at 373 K. The resulting sample evacuated at 373 K was an active catalyst for hydroformylation of ethene and partial oxidation of propene, while the Ir₄/THP/SiO₂ without evacuation exhibited poor catalytic activities. The propene oxidation reaction proceed on the Ir₄/THP/SiO₂ evacuated at 323–353 K under subatmospheric pressures to give acetone as a product in high selectivity. The ethene hydroformylation proceed on the evacuated Ir₄/THP/SiO₂ at lower temperatures compared with other conventional iridium catalysts. EXAFS characterization and kinetic studies suggested that the catalytic activities were associated with the structural distortion of the iridium cluster framework due to surface attachment by the bidentate phosphine substitution.     

Synthesis of (±)-ascochlorin, (±)-ascofuranone and LL-Z1272

Three antibiotics with a common structural feature as prenylated phenols were synthesized: (±)-ascochlorin (5 - chloro-2,4 - dihydroxy - 6 - methyl - 3 - [(2E',4/E') - 5' - (1′,2′,6′ - trimethyl - 3′-oxocyclohexyl) - 3' - methyl - 2',4' - p benzaldehyde), (±)-ascofuranone (5 - chloro - 2,4 - dihydroxy - 6 - methyl - 3 - [(2'E,6'E) - 7' - (3′,3′ - dimethyl - 4′ - oxo - 2′ - oxacyclopentyl) - 3',7 -dimethyl - 2',6' - heptadienyl] benzaldehyde) and LL-Z1272α (5 - chloro - 2,4 - dihydroxy - 6 - methyl -3 - [(2'E,6'E) - 3',7',11' - trimethyl - 2',6', 10' - dodecatrienyl] benzaldehyde)     

Poly(amine ester) dendrimer with naphthyl units as a fluorescent chemosensor for Al(III), Cu(II), and Zn(II).

A poly(amine ester) dendrimer with naphthyl units (G1N6) has been synthesized as a fluorescent chemosensor for metal ions. We investigated the metal-ion recognition of G1N6 by adding each of Ag(+), Al(3+), Ba(2+), Ca(2+), Cd(2+), Co(2+), Cu(2+), Fe(3+), Mg(2+), Ni(2+), and Zn(2+) in acetonitrile solution. Large changes were observed in the fluorescence spectra of G1N6 upon the addition of Al(3+), Cu(2+), and Zn(2+).     

Separation and quantification of monoclonal-antibody aggregates by hollow-fiber-flow field-flow fractionation

Hollow-fiber-flow field-flow fractionation (HF5) separates protein molecules on the basis of the difference in the diffusion coefficient, and can evaluate the aggregation ratio of proteins. However, HF5 is still a minor technique because information on the separation conditions is limited. We examined in detail the effect of different settings, including the main-flow rate, the cross-flow rate, the focus point, the injection amount, and the ionic strength of the mobile phase, on fractographic characteristics. On the basis of the results, we proposed optimized conditions of the HF5 method for quantification of monoclonal antibody in sample solutions. The HF5 method was qualified regarding the precision, accuracy, linearity of the main peak, and quantitation limit. In addition, the HF5 method was applied to non-heated Mab A and heat-induced-antibody-aggregate-containing samples to evaluate the aggregation ratio and the distribution extent. The separation performance was comparable with or better than that of conventional methods including analytical ultracentrifugation–sedimentation velocity and asymmetric-flow field-flow fractionation.     

Site-directed mutagenesis study on the thermal stability of a chemiric PQQ glucose dehydrogenase and its structural interpretation

We have previously reported that a chimeric pyrroloquinoline quinone (PQQ) glucose dehydrogenase (GDH), E97A3, which was made up of 97% of Escherichia coli PQQGDH sequence and 3% of Acinetobacter calcoaceticus PQQGDH, showed increased thermal stability compared with both parental enzymes. Site-directed mutagenesis studies were carried out in order to investigate the role of amino-acid substitution at the C-terminal region, Ser 771, of a chimeric PQQGDHs on their thermal stability. A series of Ser 771 substitutions of a chimeric PQQGDH, E99A1, confirmed that hydrophobic interaction governs the thermal stability of the chimeric enzymes. Comparison of the thermal denaturation of E. coli PQQGDH and E97A3 followed by far-ultraviolet (UV) circular dichroism (CD) spectroscopy revealed that E97 A3 acquired stability at the first step of denaturation, which is reversible, and where no significant secondary structure change was observed. These results suggested that the interaction between C-terminal and N-terminal regions may play a crucial role in maintaining the overall structure of β-propeller proteins.     

Generic guiding principle of HTSC material design for high-field application

Through the analyses on the irreversibility lines (ILLs) under H||c for various high-T_c superconducting (HTSC) single-crystalline samples, we found two universal functions representing ILLs. In these functions, the electromagnetic anisotropy factor γ² plays a crucial role. The appropriate chemical substitution, such as Bi(Pb)2212, is an effective method to improve flux pinning properties via decreasing γ².