New Fluorophores Based on Non-Cyclic Crown Ethers for Alkali and Alkaline Earth Metal Cation

Recent advances regarding podand derivatives which are non-cyclic crown ethers incorporating functional groups have been reviewed. Particular attention has been paid to fluorophore appended non-cyclic crown ethers as sensors for cation detection. Their complexation behavior with alkali and alkaline earth cations and interactions between their terminal groups is also discussed in detail.     

Chemical stability of La1−xSrxCrO3 in oxidizing atmospheres

The single-phase region of La_1−xSr_xCrO₃ (x=0.1, 0.2, 0.3) was precisely determined as a function of temperature, P_O2 and Sr content. The powders with the nominal composition of La_1−xSr_xCrO₃ were equilibrated under various conditions, and then identified by XRD analyses. To confirm the equilibration, two independent experiments were performed for each composition observing (i) the precipitation of the second phase from a single-phase solid solution, and (ii) the formation of the single phase from the constituent oxides. Two kinds of second phases, SrCrO₄ and an unknown phase, were observed depending on the conditions. The second phases tended to appear at low temperature, in high P_O2 and with a large Sr content. The single-phase regions obtained via the two equilibration routes were in good agreement with each other. The thermodynamic calculations on the supposition of ideality of the solid solution essentially reproduced the experimental results. When this material is used as the interconnects of solid oxide fuel cells, much attention should be paid to its relatively narrow solubility range of Sr; for example, the solubility limit is approximately 0.1 under a typical cathode-side condition (1273 K, air).     

Stable axial-rich chair conformer of myo-inositol derivatives due to introduction of two adjacent bulky silyl protections

The ring-conformational change of myo-inositol derivatives by introducing two tert-butyldimethylsilyl, triisopropylsilyl, or tert-butyldiphenylsilyl groups into the 1,2-trans hydroxy groups--3,4- and 4,5-positions--were investigated. The cyclohexane cores of the 4,5-bis-O-silylated derivatives with tert-butyldiphenylsilyl or triisopropylsilyl groups were present in the axial-rich chair form.     

Supramolecular peapods composed of a metalloporphyrin nanotube and fullerenes

An acyclic dimer of a dendritic zinc porphyrin bearing six carboxylic acid functionalities (1acid) interacts with fullerenes, such as C60 and C70, to form "supramolecular peapods", composed of a hydrogen-bonded zinc porphyrin nanotube and fullerenes (3). According to TEM, the peapods are very long (>1 mum) and have a uniform diameter of 15 nm. Without fullerenes, the zinc porphyrin dimer forms only a heavily entangled, irregular assembly. In contrast with 1acid, an ester version of the acyclic dimer without hydrogen-bonding capability (1ester) hardly interacts with fullerenes.     

Synthesis, water stability and proton conductivity of novel sulfonated polyimides from 4,4′-bis(4-aminophenoxy)biphenyl-3,3′-disulfonic acid

A novel sulfonated diamine monomer, 4,4′-bis(4-aminophenoxy)biphenyl-3,3′-disulfonic acid (BAPBDS) with the high basisity and flexible structure was synthesized by direct sulfonation of 4,4′-bis(4-aminophenoxy)biphenyl (BAPB). Sulfonated polyimides (SPIs) were prepared from 1,4,5,8-naphthalenetetracarboxylic dianhydride (NTDA), BAPBDS and nonsulfonated diamines such as BAPB. The SPI membranes showed much higher water stability at high temperatures than other sulfonated diamine-based SPIs reported so far. Their water vapor sorption isotherm, water uptake (WU), density, dimensional change and proton conductivity σ were investigated. The SPIs showed rather isotropic dimensional changes with WU and the volume increases were slightly smaller than those estimated from the additivity. The SPIs with ion exchange capacities (IECs) of 1.9–2.7 meq/g displayed the similar relationship between σ and WU each other, which was different from those of Nafion 117 and also of the SPIs with the lower IECs. The former SPIs showed reasonably high σ values of 10⁻² S/cm or more even at WU of 25 g/100 g dry polymer under 70% RH at 50 °C, whereas the latter showed the similarly high σ values only in liquid water, but not in the nearly saturated water vapor.     

Near-IR emission of Nd(III) encaged in nanosized zeolites

The near-IR emission of Nd(III) with the highest quantum yield (9.5%) in organic media was successfully observed for the first time by using bis-(perfluoromethylsulfonyl)amide (PMS) as a low vibrational ligand of the ion and TMA⁺-containing FAU zeolite nanocrystallites (TMA-nanoFAU) as a host matrix. Treatments such as deuteration and thermal treatments at high temperatures were ineffective for the strong emission of Nd(III) within TMA-nano-FAU. Judd-Ofelt analysis revealed that the ligation of PMS with the Nd(III) ion occurred easily, because the ions remained in the super cages without migrating into inner cages due to the hindrance of TMA⁺ ions occupying in the sodalite cages. The emission intensity of TMA-nano-FAU treated with PMS increased with the Nd(III)-loading level. The emission decays did not follow simple first-order kinetics and the average lifetime became longer with increasing Nd(III)-loading level. The short lifetimes at low loading levels and the long lifetimes at high loading level were attributed to Nd(PMS)₃ complexes formed with coordinating water molecules and [Nd(PMS)]-zeolite complexes without coordinating water molecules, respectively.     

Monoterpenes produced by Cupressus lusitanica cultured cells including a novel monoterpene (1s, 2s, 6s)-(+)-1,6-epoxy-4(8)-p-menthen-2-ol

A novel monoterpene, (1S, 2S, 6S)-(+)-1,6-epoxy-4(8)-p-menthen-2-ol, was isolated from an elicitor-treated cell culture of Cupressus lusitanica (Mexican cypress). Ten known monoterpenes--limonene, myrcene, beta-ocimene, sabinene, terpinolene, 4-terpineol, alpha-terpineol, 4(8)-p-menthen-1,2-diol, 4-hydroxyphellandric acid methylester and beta-thujaplicin methylether--were also identified. Regioselective metabolisms of monoterpenes were observed in this culture.     

Development of KiBank, a database supporting structure-based drug design

KiBank is a database of inhibition constant (K_i) values with 3D structures of target proteins and chemicals. K_i values were accumulated from peer-reviewed literature searched via PubMed. The 3D structure files of target proteins were originally from Protein Data Bank (PDB), while the 2D structure files of the chemicals were collected together with the K_i values and then converted into 3D ones. In KiBank, the chemical and protein 3D structures with hydrogen atoms were optimized by energy minimization and stored in MDL MOL and PDB format, respectively.

KiBank is designed to support structure-based drug design. It provides structure files of proteins and chemicals ready for use in virtual screening through automated docking methods, while the K_i values can be applied for tests of docking/scoring combinations, program parameter settings, and calibration of empirical scoring functions. Additionally, the chemical structures and corresponding K_i values in KiBank are useful for lead optimization based on quantitative structure–activity relationship (QSAR) techniques.

KiBank is updated on a daily basis and is freely available at http://kibank.iis.u-tokyo.ac.jp/. As of August 2004, KiBank contains 8000 K_i values, over 6000 chemicals and 166 proteins covering the subtypes of receptors and enzymes.     

Solution properties of celluloses from different biological origins in LiCl · DMAc

Differences in the solution properties of cellulose in 8%LiCl·DMAc (dimethyl acetamide) were investigated usingcelluloses from different origins. The latter included plants (dissolving pulp(DP), cotton linters (CC), and kraft pulp), bacteria (Acetobacterxylinum, BC), and marine animals (tunicin fromHalocynthia). The celluloses from plants and bacteriaformed LiCl·DMAc solutions that were isotropic andanisotropic, respectively; and the animal cellulose was insoluble. The weightaverage molecular weights, M_w, of DP, CC and BC were found to be98.2×10⁴,170×10⁴ and192×10⁴, respectively. The solutionviscositieswere proportional to c (c; polymer concentration) in thedilute and semi-dilute regions, where the exponent was 1 for allsamplesin the dilute region; in the semi-dilute region, it was 4 for the DP and CCsolutions and 3 for the BC solution. Molecular weight differences werecompensated by plotting the viscosity against cM_w orc[] (where [] is the limiting viscosity number).The difference in viscosity behavior at elevated solutionconcentration indicates that the cellulose molecules from DP and CC behave asflexible polymer chains and those of BC as rod-like ones.These results suggest that differences in molecular structure andproperties exist between celluloses from different sources, and that thesedifferences relate to the mechanism or the type of the intermolecularinteraction between the celluloses of plants (DP and CC) and those of bacteria(BC).     

Chemiluminescence in autoxidation of phosphonate carbanions. Phospha-1,2-dioxetanes as the most likely high-energy intermediates

Autoxidation of the phosphonate carbanions derived from 9-phosphono-10-hydroacridanes provided chemiluminescence ascribed to the excited acridone anion. The intramolecular CIEEL (chemically initiated electron exchange luminescence) mechanism can be applied to this chemiluminescence because of the much higher emission efficiency compared to that of 9-phosphono-10-methylacridanes. The effect of the phosphonate substituents on the emission efficiency and especially on the rates of the chemiluminescence decay can be interpreted to originate from the valence deviation of the phosphorus atoms, which is connected with the substituent effect on the geometrical selectivity in the olefination reaction of the phosphonate carbanions. The enhanced chemiluminescence in the presence of the fluorophores was also detected in autoxidation of the carbanions of diethyl diphenylmethylphosphonate and fluorenylphosphonate. Although the evidence is circumstantial, these results strongly support the belief that phospha-1,2-dioxetane is the most likely high-energy intermediate generating the excited molecules.