Efficient direct electron transfer with enzyme on a nanostructured carbon film fabricated with a maskless top-down UV/ozone process

We have developed a new carbon film electrode material with thornlike surface nanostructures to realize efficient direct electron transfer (DET) with enzymes, which is very important for various enzyme biosensors and for anodes or cathodes used in biofuel cells. The nanostructures were fabricated using UV/ozone treatment without a mask, and the obtained nanostructures were typically 2-3.5 nm high as confirmed by atomic force microscopy measurements. X-ray photoelectron spectroscopy and transmission electron microscopy revealed that these nanostructures could be formed by employing significantly different etching rates depending on nanometer-order differences in the local sp(3) content of the nanocarbon film, which we fabricated with the electron cyclotron resonance sputtering method. These structures could not be realized using other carbon films such as boron-doped diamond, glassy carbon, pyrolyzed polymers based on spin-coated polyimide or vacuum-deposited phthalocyanine films, or diamond-like carbon films because those carbon films have relatively homogeneous structures or micrometer-order crystalline structures. With physically adsorbed bilirubin oxidase on the nanostructured carbon surface, the DET catalytic current amplification was 30 times greater than that obtained with the original carbon film with a flat surface. This efficient DET of an enzyme could not be achieved by changing the hydrophilicity of the flat carbon surface, suggesting that DET was accelerated by the formation of nanostructures with a hydrophilic surface. Efficient DET was also observed using cytochrome c.     

Proton transport properties of poly(aspartic acid) with different average molecular weights

We synthesized seven partially protonated poly(aspartic acids)/sodium polyaspartates (P-Asp) with different average molecular weights to study their proton transport properties. The number-average degree of polymerization (DP) for each P-Asp was 30 (P-Asp30), 115 (P-Asp115), 140 (P-Asp140), 160 (P-Asp160), 185 (P-Asp185), 205 (P-Asp205), and 250 (P-Asp250). The proton conductivity depended on the number-average DP. The maximum and minimum proton conductivities under a relative humidity of 70% and 298 K were 1.7 · 10^?3 S cm^?1 (P-Asp140) and 4.6 · 10^?4 S cm^?1 (P-Asp250), respectively. Differential thermogravimetric analysis (TG-DTA) was carried out for each P-Asp. The results were classified into two categories. One exhibited two endothermic peaks between t = (270 and 300) °C, the other exhibited only one peak. The P-Asp group with two endothermic peaks exhibited high proton conductivity. The high proton conductivity is related to the stability of the polymer. The number-average molecular weight also contributed to the stability of the polymer.     

The synthetic and biological studies of discorhabdins and related compounds

Various analogues of the marine alkaloids, discorhabdins, have been synthesized. The strategy contains spirocyclization with phenyliodine(III) bis(trifluoroacetate) (PIFA), oxidative fragmentation of the β-amino alcohols with the hypervalent iodine reagent C(6)F(5)I(OCOCF(3))(2), the detosylation and dehydrogenation reaction of the pyrroloiminoquinone unit in the presence of a catalytic amount of NaN(3) and the bridged ether synthesis with HBr-AcOH as the key reactions. All the synthesized compounds were evaluated by in vitro MTT assay for cytotoxic activity against the human colon cancer cell line HCT-116. Furthermore, the discorhabdin A oxa analogues were also evaluated against four kinds of tumor model cells, a human colon cancer cell line (WiDr), a human prostate cancer cell line (DU-145) and murine leukemia cell lines (P388 and L1210). For the identification of the target, discorhabdin A and the discorhabdin A oxa analogue were evaluated by an HCC panel assay. In the test, discorhabdins could have a novel mode of action with the tumor cells.     

Enantiocontrolled total syntheses of breviones A, B, and C

Enantiocontrolled total syntheses of the breviones A, B, and C have been accomplished using a highly diastereoselective oxidative coupling of an α-pyrone with a tricyclic diene prepared from an optically pure Wieland-Miescher ketone derivative through the 7-endo-trig mode of acyl radical cyclization.     

Pycnalin, a new α-glucosidase inhibitor from Acer pycnanthum

A new compound, pycnalin (1), together with four known compounds, ginnalins A (2), B (3), C (4), and 3,6-di-O-galloyl-1,5-anhydro-D-glucitol (3,6-di-GAG) (5), were isolated from Acer pycnanthum. The structure of 1 was determined on the basis of 2D-NMR spectral data and synthesis of 1. Pycnalin (1) is the first 1,5-anhydro-D-mannitol linked to a gallic acid, while compounds 2-5 were 1,5-anhydro-D-glucitol linked to gallic acids. All compounds were tested in vitro for α-glucosidase inhibitory and 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging activities. Pycnalin (1) exhibited moderate α-glucosidase inhibitory activity as well as free radical scavenging activity. Ginnalin A (2) and 3,6-di-GAG (5), which have two galloyl groups, exhibited potent α-glucosidase inhibition, compared to those of other compounds 1, 3, and 4 containing a galloyl group. These results suggest that α-glucosidase inhibition is influenced by the number of galloyl groups.     

Exploring the thermochromism of sulfite-embedded polyoxometalate capsules

The Dawson-type polyanion [α-Mo(18)O(54)(SO(3))(2)](4-), with two SO(3)(2-) templates embedded inside a polyoxomolybdate(vi) cage, exhibits thermochromism over an exceptionally wide temperature range (～500 K). The temperature dependence of the cluster structure, established from X-ray crystallography, IR and Raman spectroscopy and DFT calculations, is related to a decreasing HOMO-LUMO gap in the near UV with increasing temperature. We postulate this is due to geometrical changes that affect both the occupied and unoccupied frontier molecular orbitals of this cluster anion.     

On canonicity of poset expansions

In this paper, we discuss the canonical extension of poset expansions. To obtain canonicity results on poset expansions, we study Ghilardi and Meloni’s canonicity methodology for Heyting algebras with unary modalities, raise the problem of extending the technique to poset expansions, and give a possible solution for the problem. Finally, we obtain a syntactic account of canonical inequalities on poset expansions consisting of constants, e_^{\epsilon_{\bot}} -additive operations, e^T{\epsilon^{\top}} -multiplicative operations, diamond, box, and strict adjoint pairs, and bounded poset expansions consisting of constants, e{\epsilon} -join preserving operations, e{\epsilon} -meet preserving operations, e{\epsilon} -additive operations, e{\epsilon} -multiplicative operations and adjoint pairs, which are more restricted than the case of lattice expansions, but can still account for Sahlqvist-like canonicity results.     

Observation of phase transition of cesium manganese hexacyanoferrates by X-ray absorption spectroscopy

Cesium manganese hexacyanoferrates exhibit an interesting phenomenon of temperature-induced phase transition accompanied by a variation in the magnetic susceptibility. We observed the variation in the electronic state of Mn during the phase transition by using X-ray absorption spectroscopy. The results of the analyses showed that the content ratio of Fe^II-CN-Mn^III and Fe^III-CN-Mn^II systematically varied during the phase transition. However, the ratio of Fe^II-CN-Mn^II remained constant at almost all temperatures. These results suggest that the charge transfer between Fe and Mn ions in the Fe^III-CN-Mn^II or the Fe^II-CN-Mn^III bond produces the phase transition.     

Thermomechanical properties and phase structure of epoxy/silica nano‐hybrid materials constructed from a linear silicone oligomer

Epoxy‐grafted silicone oligomer (ESO), which has a linear silicone chain in the backbone moiety, was synthesized from a trifunctional alkoxysilane via a sol–gel reaction. Characterization of ESO was performed with ¹H and ²⁹Si NMR, Fourier transform infrared, and gel permeation chromatography. The number‐average molecular weight of ESO was 3300. By adding the silicone oligomer as the inorganic source in the curing process of the epoxy resin, novel epoxy/silica hybrid materials were prepared. It was observed by transmission electron microscope that fine silica‐rich domains of about 5‐nm diameter were uniformly dispersed in the cured epoxy matrix. Thermomechanical properties of the hybrid materials were also investigated. The storage modulus in the rubbery region and the peak area of the tan δ curve at the glass‐transition region increased and decreased, respectively, with the hybridization of the silica network. The mobility of the epoxy network chains should be considerably suppressed by the hybridization with the silica network. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 1631–1639, 2005