Tricycloclavulone and clavubicyclone, novel prostanoid-related marine oxylipins, isolated from the Okinawan soft coral Clavularia viridis

Two novel prostanoid-related marine oxylipins, tricycloclavulone (1) and clavubicyclone (2), were isolated from the Okinawan soft coral Clavularia viridis. The structures of 1, having a tricyclo[5.3.0.0(1,4)]decane ring system, and 2, having a bicyclo[3.2.1]octane ring system, were elucidated on the basis of spectroscopic analysis. Clavubicyclone showed a moderate growth inhibition activity against tumor cells in vitro.     

An integrated microfluidic device in polyester for electrophoretic analysis of amino acids

A precolumn reaction chamber was integrated into a polyester microfluidic device with a miniaturized detection system. The reaction chamber was designed to be a zigzag channel, 70 microm in width, 8 mm in length, followed by a wider straight channel, 150 microm in width, 2 mm in length. The detection system is composed of an embedded light-emitting diode (LED), an integrated optical fiber, and a photomultiplier tube (PMT). A success in amino acid analysis using the integrated microchemical analysis device proved that the precolumn reaction chamber was compatible with the integrated detection system. Three kinds of amino acids, arginine, glycine, and phenylalanine, mixed and reacted with 7-fluoro-4-nitrobenzo-2-oxa-1,3-diazole (NBD-F) in the precolumn reaction chamber to produce fluorescent products, were separated by micellar eletrokinetic chromatography (MEKC) and detected by LED-excited fluorescence. The detection limits for arginine, glycine, and phenylalanine were 1, 1, and 0.5 mM, respectively, which can be improved by further optimizations of the reaction system and detection system.     

Quasi one-dimensional nanopores in single-wall carbon nanohorn colloids using grand canonical Monte Carlo simulation aided adsorption technique

The average interstitial nanopore structure of single-wall carbon nanohorn (SWNH) assemblies was determined using X-ray diffraction and grand canonical Monte Carlo (GCMC) simulation aided N(2) adsorption at 77 K. The interstitial nanopores of SWNH assemblies can be regarded as quasi one-dimensional pores due to the partial orientation of the SWNH particles; the average pore width of the interstitial pores is 0.6 nm. Good agreement between the GCMC simulation of a structural model with one-dimensional interstitial nanopores and an experimental adsorption isotherm below P/P(0) = 10(-4) is evidence of the quasi one-dimensionality of the interstitial nanopores. A snapshot from the GCMC simulation showed one-dimensional growth of adsorbed N(2) molecules.     

Opening mechanism of internal nanoporosity of single-wall carbon nanohorn

Single-wall carbon nanohorn (SWNH), which is a tubular particle with a cone cap, was oxidized in an oxygen flow at various temperatures. N(2) adsorption at 77 K, thermogravimetry (TG), differential thermal analysis (DTA), transmission electron microscopy, and Raman spectroscopy measurements were carried out on the oxidized SWNHs. The specific surface area of the oxidized SWNHs can be controlled by oxidation temperature, giving the maximum value of 1420 m(2)/g. The pore size distribution by the BJH method and the comparison plot of the N(2) adsorption isotherms of SWNH oxidized at different temperatures against that of as-grown SWNH revealed the minimum oxidation temperature for opening internal nanopores. TG-DTA analyses determined the components of as-grown SWNH: amorphous carbon 2.5 wt %, defective carbon at the cone part 15 wt %, tubular carbon 70 wt %, and graphitic carbon 12 wt %. These systematic analyses provided the exact internal nanopore volume of 0.49 mL/g for pure SWNH particles.     

Active site mapping of 2-deoxy-scyllo-inosose synthase, the key starter enzyme for the biosynthesis of 2-deoxystreptamine. Mechanism-based inhibition and identification of lysine-141 as the entrapped nucleophile

A key enzyme in the biosynthesis of clinically important aminoglycoside antibiotics including neomycin, kanamycin, gentamicin, etc. is 2-deoxy-scyllo-inosose synthase (DOIS), which catalyzes the carbocycle formation from d-glucose-6-phosphate to 2-deoxy-scyllo-inosose (DOI). To clarify its precise reaction mechanism and crucial amino acid residues in the active site, we took advantage of a mechanism-based inhibitor carbaglucose-6-phosphate (pseudo-dl-glucose, C-6-P) with anticipation of its conversion to a reactive alpha,beta-unsaturated carbonyl intermediate. It turned out that C-6-P clearly showed time- and concentration-dependent inhibition against DOIS, and the molecular mass of the resulting modified-DOIS with C-6-P was 160 mass units larger than that of native DOIS. Thus, the expected alpha,beta-unsaturated intermediate appeared to trap a specific nucleophilic group in the active site through the Michael-type 1,4-addition. The covalently modified amino acid residue was determined to be Lys-141 by means of enzymatic digestion and subsequent LC/MS and LC/MS/MS of the digest. Also discussed are the role of Lys-141 in the substrate recognition and the reaction pathway and comparison with evolutionary related dehydroquinate synthase.     

Molecular assembly of C2-symmetric Bis-(2S)-2-methyldodecanoylamides of alpha,omega-alkylidenediamines into coiled coil and twisted ribbon aggregates

A series of 10 didodecanoylamides of alpha,omega-alkylidenediamines bridged by a straight carbon chain varying in length from 0 to 9 carbons was examined as possible gelator molecules of organic liquids to gain information on the relationships between the spacial arrangement of two amide groups in a molecule and their effects on the microscopic structures of the gel. The structural characteristics of these amides are parallel and antiparallel arrangements of two amide carbonyl groups, which depend on the even and odd numbers of a bridging zigzag carbon chain. The linear alkyl chain moieties and a center carbon chain of diamides intermolecularly interact with each other within the van der Waals contact. Two amide moieties of an even number carbon chain diamide intermolecularly interact with each other by using two pairs of hydrogen bonds with two other molecules in a plane, which formed ribbonlike self-complementarily assembled aggregates. On the other hand, a diamide of an odd number carbon chain forms four independent hydrogen bonds with four other molecules not in a plane, which assembled into woven aggregates. Asymmetric introduction of a methyl group at the alpha-position of the amide groups successfully twists the two side chain van der Waals cores of the chiral diamides in the fixed direction, giving helically twisted ribbon and coiled coil aggregates. The helically twisted ribbon and coiled coil aggregates of these chiral diamides were directly observed by CD, SEM, and TEM, providing a basis for the design of a sophisticated small molecular gelator of a tailor-made shape.     

Alkali effects on the electronic states of K3C60 and Rb3C60

The electronic states in metallic alkali fullerides K₃C₆₀ and Rb₃C₆₀, are studied in detail by cw- and pulsed-ESR. The ESR linewidth associated with conduction electrons varies substantially, depending sensitively on the alkali metals used. It is clearly revealed that the linewidth is homogeneous and is strongly controlled by the spin-lattice relaxation times (T₁) determined via the spin-orbit interactions of the small fraction of s electrons remaining on the alkali atoms. The results indicate that the electron transfer from the alkali atoms to C₆₀ is not perfectly complete, with the remaining fraction being much greater in the tetrahedral sites than in the octahedral sites of the face-centered cubic lattice.     

Preparation and characterization of DNA films induced by UV irradiation

Large amounts of DNA-enriched materials, such as salmon milts and shellfish gonads, are discarded as industrial waste. We have been able to convert the discarded DNA to a useful material by preparing novel DNA films by UV irradiation. When DNA films were irradiated with UV light, the molecular weight of DNA was greatly increased. The reaction was inhibited by addition of the radical scavenger galvinoxyl suggesting that the DNA polymerization with UV irradiation proceeded by a radical reaction. Although this UV-irradiated DNA film was water-insoluble and resistant to hydrolysis by nuclease, the structure of the DNA film in water was similar to non-irradiated DNA and maintained B-form structure. In addition, the UV-irradiated DNA film could effectively accumulate and condense harmful DNA-intercalating compounds, such as ethidium bromide and acridine orange, from diluted aqueous solutions. The binding constant and exclusion number of ethidium bromide for UV-irradiated DNA were determined to be 6.8 +/- 0.3 x 10(4) M(-1) and 1.6 +/- 0.2, respectively; these values are consisted with reported results for non-irradiated DNA. The UV-irradiated DNA films have potential uses as a biomaterial filter for the removal of harmful DNA intercalating compounds.     

Palladium nanoclusters deposited on single-walled carbon nanohorns

This study reports a direct route for deposition of Pd nanoclusters on single-walled carbon nanohorns (SWNHs) in a one step reaction involving chemical reduction of metal ions in the presence of a polymer-stabilizer. The applied strategy provides small Pd nanoclusters with an average diameter of approximately 2.3 nm robustly attached to the nanotubular carbon. The attachment is mediated by the polymer (poly(vinylpyrrolidone), PVP) used to stabilize the nanoclusters.     

Formation of β- and β″-Al2O3 by the solid state reaction between NaAlO2 and γ-Al2O3

The solid state reaction of NaAlO₂ with γ-Al₂O₃ was investigated kinetically. Powdered compacts with various compositions (Al₂O₃/NaAlO₂ = 1–5) were fired at 700–1200°C for 1–768 hr. The amounts of the reaction product were determined by peak heights of X-ray diffraction patterns. β″-Al₂O₃ was formed predominantly from the sample with Al₂O₃/NaAlO₂ = 2. The firing time for the β″-Al₂O₃ formation was shortened as the firing temperature was raised, and the activation energy, E_a, for formation was about 130–135 kcal/mole. The sample of Al₂O₃/NaAlO₂ = 5 formed m-Al₂O₃ with the mullite structure and was observed to transform gradually to β-Al₂O₃. E_a for the m-Al₂O₃ formation and for the transition were about 55–60 and 40 kcal/mole, respectively, which resulted in E_a of about 95–100 kcal/mole for the β-Al₂O₃ formation. The mechanism of the m-Al₂O₃ formation is discussed briefly.