Inorganic-organic hybrid membranes with anhydrous proton conduction prepared from 3-aminopropyltriethoxysilane and sulfuric acid by the sol-gel method

Inorganic-organic hybrid membranes with anhydrous proton conduction were prepared from 3-aminopropyltriethoxysilane and H2SO4 by the sol-gel method. The membrane has a unique structure: a hexagonal phase formed by the stacking of rodlike polysiloxanes with ion complexes of ammonium groups and HSO4- extruded outside. The membranes showed high conductivity of 2 x 10-3 S cm-1 at 200 degrees C under dry atmosphere. In the membrane, protons probably migrate through the outside of the rodlike polysiloxanes along hydrogen-bond chains formed among HSO4- anions.     

Quantum oscillation of the tunneling conductance in fully epitaxial double barrier magnetic tunnel junctions

We investigated spin-dependent tunneling conductance properties in fully epitaxial double MgO barrier magnetic tunnel junctions with layered nanoscale Fe islands as a middle layer. Clear oscillations of the tunneling conductance were observed as a function of the bias voltage. The oscillation, which depends on the middle layer thickness and the magnetization configuration, is interpreted by the modulation of tunneling conductance due to the spin-polarized quantum well states created in the middle Fe layer. This first observation of the quantum size effect in the fully epitaxial double barrier magnetic tunnel junction indicates great potential for the development of the spin-dependent resonant tunneling effect in coherent tunneling regime.     

Development of a linear type of low molecular weight CXCR4 antagonists based on T140 analogs

A linear type of several low molecular weight CXCR4 antagonists were developed based on T140 analogs, which were previously found to be strong CXCR4 antagonists that block X4-HIV-1 entry and have inhibitory activities against cancer metastasis/progression and rheumatoid arthritis.     

Staminolactones A and B and norstaminol A: three highly oxygenated staminane-type diterpenes from Orthosiphon stamineus

[formula: see text] Staminolactones A (1) and B (2) and norstaminol A (3), three highly oxygenated staminane-type diterpenes having mild cytotoxic activities against highly liver-metastatic colon 26-L5 carcinoma cells, were isolated from the aerial part of the Vietnamese medicinal plant Orthosiphon stamineus (Lamiaceae). Their structures were elucidated on the basis of the extensive spectral analyses.     

High-performance liquid chromatographic assay of N(G)-monomethyl-L-arginine, N(G),N(G)-dimethyl-L-arginine, and N(G),N(G)'-dimethyl-L-arginine using 4-fluoro-7-nitro-2, 1,3-benzoxadiazole as a fluorescent reagent

N(G)-Monomethyl-L-arginine (L-NMMA), N(G),N(G)-dimethyl-L-arginine (ADMA), and N(G),N(G)'-dimethyl-L-arginine (SDMA) are emerging cardiovascular risk factors. A high-performance liquid chromatographic method with fluorescence detection for the simultaneous determination of L-NMMA, ADMA and SDMA is described. The assay employed 4-fluoro-7-nitro-2,1,3-benzoxadiazole (NBD-F) as a fluorescent derivatization reagent. After solid phase extraction with cation-exchange column, the methylated arginines were converted to fluorescent derivatives with NBD-F, and the derivatives were separated within 32 min on a reversed-phase column. Nomega-Propyl-L-arginine was Used as an internal standard. Extrapolated detection limits were 12 nM (12 fmol per injection) for L-NMMA and 20 nM (20 fmol per injection) for ADMA and SDMA, respectively, with a signal-to-noise ratio of 3. The calibration curves for L-NMMA, ADMA and SDMA were linear within the range of 50-5000 fmol. The method was applied to the quantitative determination of L-NMMA, ADMA and SDMA in 200 microl of rat plasma. The concentrations of L-NMMA, ADMA and SDMA in rat plasma were 0.16 +/- 0.03, 0.80 +/- 0.25 and 0.40 +/- 0.21 microM, respectively (n = 5).     

Water Accessibilities of Man-made Cellulosic Fibers – Effects of Fiber Characteristics

The dynamic vapor water sorption and desorption experiments were performed on cellulosic fibers with different characteristics. The hysteresis between moisture sorption and desorption cycle at 10% relative humidity (RH) was independent on the total moisture regain and approximately 45% for all materials except for viscose fibers. Brunauer–Emmett–Teller surface volume (V_m) for moisture sorption and retention capacity of liquid water (WRV) were also measured. The V_m and WRV increase in proportion to the total amount of moisture sorption (M_inf(total)) in all specimen except in poplar fiber. The coefficients of parallel exponential kinetics (PEK) were estimated by the curve-fitting of experimental data of the moisture regain, and the influences of the fiber characteristics on the PEK coefficients, the moisture regain, the hysteresis, V_m and WRV are discussed. The total equilibrium moisture content in the viscose fibers was higher but the moisture uptake and release rate was slower than the lyocell and poplar fibers. The cationization and the modification of shape of cross section accelerated the total equilibrium moisture content in the viscose fiber. A drying process at low temperature enhanced both the equilibrium moisture content and the moisture uptake and release rate in lyocell fibers while a spin finish retarded them. The total equilibrium moisture content was heightened by the crosslinking of the fiber, however, no obvious effect of the crosslinking on the moisture uptake and release rate was found. Effects of the type of the specimen and linear density on the moisture accessibilities are also discussed.     

Epicalyxin F and calyxin I: two novel antiproliferative diarylheptanoids from the seeds of Alpinia blepharocalyx

[formula: see text] Epicalyxin F (1) and calyxin I (2), two novel diarylheptanoids, were isolated from a residual fraction of an EtOH extract of Alpinia blepharocalyx. Calyxin I (2) represented a new carbon skeleton, and epicalyxin F (1) possessed potent antiproliferative activity toward HT-1080 fibrosarcoma and colon 26-L5 carcinoma with ED50 values of 1.71 and 0.89 microM, respectively.     

Extended hypervalent 5c-6e interactions: linear alignment of five C-Se---O---Se-C atoms in anthraquinone and 9-methoxyanthracene bearing arylselanyl groups at the 1,8-positions

The structures of 1,8-bis(phenylselanyl)anthraquinone (1a), 1,8-bis(phenylselanyl)-9-methoxyanthracene (2a), and 1,8-bis(phenylselanyl)anthracene (3a) are determined by X-ray crystallographic analysis, together with the derivatives. The Se-C(i) (Ph) bonds in 1a are placed on the anthraquinone plane (both type B) and the phenyl planes are perpendicular to the anthraquinone plane. The structure around the Se atoms in 2a is very close to that of 1a: the conformations of the PhSe groups are both type B. Consequently, the five C(i)-Se- - -O- - -Se-C(i) atoms in 1a and 2a align linearly. The nonbonded Se- - -O distances in 1a and 2a are 2.673-2.688 and 2.731-2.744 A, respectively, which are about 0.7 A shorter than the sum of van der Waals radii of the atoms. The extended hypervalent sigma*(C(i)-Se)- - -n(p)(O)- - -sigma*(Se-C(i)) 5c-6e interactions are strongly suggested for the origin of the linear alignment of the five atoms in 1a and 2a. The 5c-6e must be constructed by the connection of the two hypervalent n(p)(O)- - -sigma*(Se-C(i)) 3c-4e interactions through the central n(p)(O). The five C(i)-Se- - -H- - -Se-C(i) atoms never align linearly in 3a. To reveal the nature of 5c-6e in 1a and 2a, QC calculations are performed on H(a)H(b)(A)Se- - -O([double bond]CH(2))- - -(B)SeH(a')H(b') (model a) and H(a)H(b)(A)Se- - -OH(2)- - -(B)SeH(a')H(b') (model b) with the B3LYP/6-311++G(3df,2pd) method, where the nonbonded Se- - -O distances are fixed at 2.658 A. Four conformers, a (AA-cis), a (AA-trans), a (AB), and a (BB), are optimized to be stable for model a, where a (AA) shows both type A for the (A)Se-H(b) and (B)Se-H(b') bonds in model a. Three conformers, b (AA-cis), b (AB), and b (BB), are stable for model b. The bonding models in AA, AB, and BB correspond to 3c-6e, 4c-6e, and 5c-6e, respectively. The models become more stable by 42 +/- 5 kJ mol(-1), if the type A conformation of each Se-H bond changes to type B. No noticeable saturation is observed in the stabilization for each change. QC calculations are also performed on 1a-3a at the B3LYP level. Three conformers are evaluated to be stable for 1a and 2a. The relative energies of 1a (AA-trans), 1a (AB), and 1a (BB) are 0.0, -31.5, and -60.6 kJ mol(-1), respectively, and those of 2a (AA-cis), 2a (AB), and 2a (BB) are 0.0, -24.4, and -36.5 kJ mol(-1), respectively. These results demonstrate that the origin of the linear alignment of the five C-Se- - -O- - -Se-C atoms in 1a and 2a is the energy lowering effect by the extended hypervalent 5c-6e interactions of the sigma*(C-Se)<--n(p)(O)-->sigma*(Se-C) type. The pi-conjugation between pi(C[double bond]O) and n(pz)(Se) through the pi-framework of anthraquinone must also contribute to stabilize the BB structure of 1a, where z is the direction perpendicular to the anthraquinone plane.