Development of a chemical vapor sensor using piezoelectric quartz crystals with coated unusual lipids

Piezoelectric quartz crystal sensors were developed using lipids with various properties for highly sensitive detection of chemical vapors. Lipids with varying lengths of alkyl chains were coated onto 10 MHz AT-cut quartz crystal resonators and the response of these modified crystals to chemical vapors were measured. It was shown that hydrophilic compounds, such as ethanol and methanol, could be recognized efficiently by lipids having shorter alkyl chains, whereas lipids with longer alkyl chains showed affinity to more hydrophobic vapors, such as toluene, hexane and cyclohexane. Frequency changes caused by adsorption of alcohols could be enhanced when cholesterol was co-immobilized in the lipid layer. To confirm the assumption that the sensor-response might be affected by the properties of lipids derived from acyl chains, we have examined the effects of two types of newly synthesized unusual lipids on sensor response. When lipids having one triple bond each at different positions on their alkyl chains were coated onto quartz crystals separately, lower responses were observed compared to responses obtained for a sensor with immobilized, saturated phosphatidylcholine. Lipids containing -branched acyl chains, however, showed good affinity for organic vapors, and sensor responses improved 4–5-fold. Moreover, these sensors were shown to have sensitivity of the same order as the humans' sense of smell (10⁻⁵–10⁻⁶ w/w in liquid paraffin) when measured using standard odorants (isovaleric acid, skatole, etc.) for an olfactometry established in Japan.     

Metallation of aliphatic carbon atoms: II,syntheses and characterization of the cyclopalladated complexes of N,N-dimethylneopentylamine

N,N-Dimethylneopentylamine reacts with Pd(MeCO₂)₂ to give a novel trinuclear cyclopalladated complex [Me₂NCH₂CMe₂CH₂Pd(μ-MeCO₂)₂Pd(μ-MeCO₂)₂PdCH₂CMe₂CH₂NMe₂]?-0.5C₆H₆ (I). The reaction of I with PPh₃ affords both trans-[Pd(MeCO₂)₂(PPh₃)₂] (II) and [Pd(CH₂CMe₂CH₂NMe₂)(MeCO₂)(PPh₃)] (III). The reaction of III with LiCl yields a mononuclear cyclopalladated complex, [Pd(CH₂CMe₂CH₂NMe₂)Cl(PPh₃)] (IV).     

Influence of the Coordination of Donor Solvent Molecules to 1,4,7,10-Tetramethyl-1,4,7,10- tetraazacyclododecanenickel(II) and Analogous Nickel(II) Complexes on Their Steric Factors

Coordination equilibrium constants (K _NiS) of some donor solvent molecules to 1,4,7,10-tetramethyl-1,4,7,10-tetraazacyclododecanenickel(II) ([Ni(Me₄[12]aneN₄)]²⁺) were determined in nitrobenzene (a noncoordinating bulk solvent). The first (K _NiS1) and second stepwise coordination equilibrium constants (K _NiS2) for 1,4,7,10-tetraazacyclododecanenickel(II) ([Ni([12]aneN₄)]²⁺), 1,4,8,11-tetraazac yclotetradecane- nickel(II) ([Ni([14] aneN₄)]²⁺), 1,4,8,11-tetrathiacyclotetra-decanenickel(II) ([Ni([14]aneS₄)]²⁺) were also reinvestigated. The K _NiS values for [Ni(Me₄[12]aneN₄)]²⁺ were compared to those of [Ni([12]aneN₄)]²⁺, (1R,4S, 8R,11S)-1,4,8,11-tetramethyl-1,4,8,11-tetraazacyclotetradecanenickel(II) (R,S,R,S-[Ni(Me₄[14]aneN₄)]²⁺), R,R,S,S-[Ni(Me₄[14]aneN₄)]²⁺, [Ni([14]aneN₄)]²⁺, and [Ni([14]aneS₄)]²⁺. Coordination of pyridine (Py), N,N,N′,N′-tetramethylurea (TMU), and N,N-dimethylacetamide (DMA) to [Ni(Me₄[12]aneN₄)]²⁺ was observed, although these donor solvent molecules did not coordinate to R,S,R,S-[Ni(Me₄[14]aneN₄)]²⁺. The K _NiS values for Py, TMU, and DMA are 7.9, 2.8, and 9.0 dm³⋅mol⁻¹, respectively. Some hydrogen-bonding waters were coordinated to R,S,R,S-[Ni(Me₄[14]aneN₄)]²⁺, but such waters did not coordinate to [Ni(Me₄[12] aneN₄)]²⁺. Also, the K _NiS2 values were larger than the corresponding K _NiS1 values for [Ni([14]aneS₄)]²⁺. Furthermore, the K _NiS1 values for [Ni([12]aneN₄)]²⁺ were the largest among these nickel(II) complex cations. The K _NiS, K _NiS1, and K _NiS2 values are discussed in terms of properties of the donor solvents and steric strains of these nickel(II) complex cations.     

High-performance liquid chromatographic identification of disaccharides generated from heparan sulphate isomers using heparitinases

Specific heparan sulphate-lyases, heparitinases I and II, were used to identify unsaturated disaccharide constituents generated from heterogeneous heparan sulphate isomers. All determinations were made using high-performance liquid chromatography with a column containing a sulphonized styrene-divinylbenzene copolymer. Unsaturated disaccharides generated from variously sulphated heparan sulphate isomers after simultaneous digestion with heparitinases I and II facilitated separation of the individual disaccharides, based on sulphate groups at the specific position of the uronic acid and glucosamine residues. The simultaneous digestion with heparitinases I and II produces unsaturated disaccharides from heparan sulphate isomers with the structure of 4-deoxy-2-O-alpha-L-threo-hex-4-enepyranosyluronic acid (1----4)-2-amino-deoxy-D-glucose, 4-deoxy-2-O-alpha-L-threo-hex-4-enepyranosyluronic acid (1----4)-2-deoxy-2-sulphamido-D-glucose, 4-deoxy-2-O-alpha-L-threo-hex-4-enepyranosyluronic acid (1----4)-2-aminodeoxy-6-O-sulpho-D-glucose, 4-deoxy-2-O-alpha-L-threo-hex-4-enepyranosyluronic acid (1----4)-2-deoxy-2-sulphamido-6-O-sulpho-D-glucose, 4-deoxy-2-O-sulpho-alpha-L-threo-hex-4-enepyranosyluronic acid (1----4)-2-amino-2-deoxy-6-O-sulpho-D-glucose and 4-deoxy-2-O-sulpho-alpha-L-threo-hex-4-enepyranosyluronic acid (1----4)-2-deoxy-2-sulphamido-6-O-sulpho-D-glucose.     

Formation Thermodynamics of Binary and Ternary Lanthanide(III) Complexes with 1,10-Phenanthroline and Chloride in N,N-Dimethylformamide

Formation thermodynamics of binary and ternary lanthanide(III) (Ln = La, Ce, Nd, Eu, Gd, Dy, Tm, Lu) complexes with 1,10-phenanthroline (phen) and the chloride ion have been studied by titration calorimetry and spectrophotometry in N,N-dimethyl-formamide (DMF) containing 0.2 mol-dm^–3 (C₂H₅)₄NClO₄ as a constant ionic medium at 25°C. In the binary system with 1,10-phenanthroline, the Ln(phen)³⁺ complex is formed for all the lanthanide(III) ions examined. The reaction enthalpy and entropy values for the formation of Ln(phen)³⁺ decrease in the order La > Ce > Nd, then increase in the order Nd < Eu < Gd < Dy, and again decrease in the order Dy > Tm > Lu. The variation is explained in terms of the coordination structure of Ln(phen)³⁺ that changes from eight to seven coordination with decreasing ionic radius of the metal ion. In the ternary Ln³⁺-Cl^–-phen system, the formation of LnCl(phen)²⁺, LnCl₂(phen)⁺, and LnCl₃(phen) was established for cerium(III), neodymium(III), and thulium(III), and their formation constants, enthalpies, and entropies were obtained. The enthalpy and entropy values are also discussed from the structural point of view.     

Modes of conformational changes of proteins adsorbed on a planar hydrophobic polymer surface reflecting their adsorption behaviors

Infrared spectra of hen egg white lysozyme and bovine serum albumin (BSA) adsorbed on a solid poly tris(trimethylsiloxy)silylstyrene (pTSS) surface in D2O solution were measured using attenuated total reflection (ATR) Fourier transform infrared spectroscopy. From the area and shape of the amide I' band of each spectrum, the adsorption amount and the secondary structure were determined simultaneously, as a function of adsorption time. We could show that the average conformation for all the adsorbed lysozyme molecules was solely determined by the adsorption time, and independent of the bulk concentration, while the adsorption amount increased with the bulk concentration as well as the adsorption time. These results suggest that lysozyme molecules form discrete assemblies on the surface, and that the surface assemblies grow over several hours to have a definite architecture independent of the adsorption amount. As for BSA, the extent of the conformational change was solely determined by the adsorption amount, regardless of the bulk concentration and the adsorption time. These differences in the adsorption properties of lysozyme and BSA may reflect differences in their conformational stabilities.     

Synthesis and complexing properties of bis-crown ethers incorporating benzo-15-crown-5 and metallocene

Bis-crown ethers in which the benzo-15-crown-5 units were linked to 1,1′-positions of metallocene (M = Fe or Ru) with amide, ester, or ? C? C? bonds were synthesized. Complexing ability of the compounds with alkali, alkali earth, and transition metal cations were measured by the solvent extraction method. The results showed that these crown ethers had high affinity toward alkali metal cations (Li⁺, Na⁺, K⁺, and Rb⁺) and heavy-metal cations (Ag⁺ and Tl⁺). The difference of complexing ability for metal cations between ferrocene and ruthenocene derivatives could not be detected significantly. The extractability of metallocene-bis-crown ethers for metal cations was more larger than that of the corresponding mono-crown ethers, and irregular increments of extractability were explained by assuming the existence of a mixture of 1:1 and 2:1 complexes.     

Release kinetics of nicotinamide from fatty acid-nicotinamide equimolar complexes. II. Activation thermodynamic quantities.

The rates of release of nicotinamide (NAA) from fatty acid (FA)-NAA complexes, FA-NAA, were determined at various temperatures, and the thermodynamic quantities for the release of NAA were estimated. The results were compared with the previous results obtained for FA-thiamine disulfide (TDS) complexes, (FA)6(TDS). The values of activation enthalpy (delta H ++) and activation entropy (delta S ++) for the release of NAA from FA-NAA were positive and negative, respectively, indicating that the release of NAA is disadvantageous from not only enthalpic but also entropic viewpoints. The plots of delta H++ against the carbon number (n) in the constituent FA showed a zig-zag line with an upward convex at an odd-numbered position and the plots of the absolute values of (-delta S++) showed a zig-zag line with a downward convex at an odd-numbered position, though the positive value of delta H++ increases and the negative value of delta S++ decreases with an increasing n for either even-numbered or odd-numbered FA. It was found that the release of NAA from FA-NAA formed with odd-numbered FA is more disadvantageous enthalpically but more advantageous entropically as compared with that from FA-NAA formed with even-numbered FA. This phenomenon was similar to that observed for (FA)6(TDS). Furthermore, it is suggested that FA-NAA is formed at least by van der Waals forces and hydrophobic interactions and that van der Waals forces are dominant for the formation of FA-NAA formed with odd-numbered FA and that hydrophobic interactions are dominant for the formation of FA-NAA formed with even-numbered FA.     

Assembly of Carbohydrates on a Nickel(II) Center by Utilizing N-Glycosidic Bond Formation with Tris(2-aminoethyl)amine (tren). Syntheses and Characterization of [Ni{N-(aldosyl)-tren}(H(2)O)](2+), [Ni{N,N'-bis(aldosyl)-tren}](2+) and [Ni{N,N',N"-tris(aldosyl)-tren}](2+)

Reactions of [Ni(tren)(H(2)O)(2)]X(2) (tren = tris(2-aminoethyl)amine; X = Cl (1a), Br (1b); X(2) = SO(4) (1c)) with mannose-type aldoses, having a 2,3-cis configuration (D-mannose and L-rhamnose), afforded {bis(N-aldosyl-2-aminoethyl)(2-aminoethyl)amine}nickel(II) complexes, [Ni(N,N'-(aldosyl)(2)-tren)]X(2) (aldosyl = D-mannosyl, X = Cl (2a), Br (2b), X(2) = SO(4) (2c); aldosyl = L-rhamnosyl, X(2) = SO(4) (3c)). The structure of 1c was confirmed by X-ray crystallography to be a mononuclear [Ni(II)N(4)O(2)] complex with the tren acting as a tetradentate ligand (1c.2H(2)O: orthorhombic, Pbca, a = 15.988(2) ?, b = 18.826(4) ?, c = 10.359(4) ?, V = 3118 ?(3), Z = 8, R = 0.047, and R(w) = 0.042). Complexes 2a,c and 3c were characterized by X-ray analyses to have a mononuclear octahedral Ni(II) structure ligated by a hexadentate N-glycoside ligand, bis(N-aldosyl-2-aminoethyl)(2-aminoethyl)amine (2a.CH(3)OH: orthorhombic, P2(1)2(1)2(1), a = 16.005(3) ?, b = 20.095(4) ?, c = 8.361(1) ?, V = 2689 ?(3), Z = 4, R = 0.040, and R(w) = 0.027. 2c.3CH(3)OH: orthorhombic, P2(1)2(1)2(1), a = 14.93(2) ?, b = 21.823(8) ?, c = 9.746(2) ?, V = 3176 ?(3), Z = 4, R = 0.075, and R(w) = 0.080. 3c.3CH(3)OH: orthorhombic, P2(1)2(1)2(1), a = 14.560(4) ?, b = 21.694(5) ?, c = 9.786(2) ?, V = 3091 ?(3), Z = 4, R = 0.072, and R(w) = 0.079). The sugar part of the complex involves novel intramolecular sugar-sugar hydrogen bondings around the metal center. The similar reaction with D-glucose, D-glucosamine, and D-galactosamine, having a 2,3-trans configuration, resulted in the formation of a mono(sugar) complex, [Ni(N-(aldosyl)-tren)(H(2)O)(2)]Cl(2) (aldosyl = D-glucosyl (4b), 2-amino-2-deoxy-D-glucosyl (5a), and 2-amino-2-deoxy-D-galactosyl (5b)), instead of a bis(sugar) complex. The hydrogen bondings between the sugar moieties as observed in 2 and 3 should be responsible for the assembly of two sugar molecules on the metal center. Reactions of tris(N-aldosyl-2-aminoethyl)amine with nickel(II) salts gave the tris(sugar) complexes, [Ni(N,N',N"-(aldosyl)(3)-tren)]X(2) (aldosyl = D-mannosyl, X = Cl (6a), Br (6b); L-rhamnosyl, X = Cl (7a), Br (7b); D-glucosyl, X = Cl (9); maltosyl, X = Br (10); and melibiosyl, X = Br (11)), which were assumed to have a shuttle-type C(3) symmetrical structure with Delta helical configuration for D-type aldoses on the basis of circular dichroism and (13)C NMR spectra. When tris(N-rhamnosyl)-tren was reacted with NiSO(4).6H(2)O at low temperature, a labile neutral complex, [Ni(N,N',N"-(L-rhamnosyl)(3)-tren)(SO(4))] (8), was successfully isolated and characterized by X-ray crystallography, in which three sugar moieties are anchored only at the N atom of the C-1 position (8.3CH(3)OH.H(2)O: orthorhombic, P2(1)2(1)2(1), a = 16.035(4) ?, b = 16.670(7) ?, c = 15.38(1) ?, V = 4111 ?(3), Z = 4, R = 0.084, and R(w) = 0.068). Complex 8 could be regarded as an intermediate species toward the C(3) symmetrical tris(sugar) complexes 7, and in fact, it was readily transformed to 7b by an action of BaBr(2).     

Characterization of fibril reinforced membranes for fuel cells

Characteristics of fibril reinforced membranes developed by Asahi Glass Company are reviewed. PTFE-fibrils <1 μm in diameter are dispersed in ion-exchange membranes uniformly. Mechanical properties, such as tensile strength, tear strength, creep property and compressive property were examined and compared with non-reinforced membranes. Fibril reinforced membranes, even by the addition of a small amount of PTFE-fibrils (2.7 wt.%), show excellent mechanical strength, especially in creep and tear strength. Cell performance is nearly equal to the one using a non-reinforced membrane and cell voltage stays about the same during the cell operation at 80 °C for 3000 h.