Stability of crown ether complexes: a mo theoretical study

Calculation using CNDO/2 method have been performed for the crown ethers and their cation complexes. The photoelectron spectra of 18-crown-6 and 12-crown-4 are well described by the present MO calculations. The orbital interactions between the crown ligand and the cation indicate the importance of the charge transfer interaction for the complex formation. The destabilization energy due to the ring-shrinking (~ 0.5 eV) is very small compared with the complexation energy (5–8 eV). The stability of the complex was reasonably explained by the considering the hydrated species of the cation and the complex, indicating the important role of the solvation effect in the selectivity of the crown ether to the cation.     

Beta-1,3-glucan polysaccharides as novel one-dimensional hosts for DNA/RNA, conjugated polymers and nanoparticles

Beta-1,3-glucan polysaccharides have triple-stranded helical structures whose sense and pitch are comparable to those of polynucleotides. We recently revealed that the beta-1,3-glucans could interact with certain polynucleotides to form triple-stranded and helical macromolecular complexes consisting of two polysaccharide-strands and one polynucleotide-strand. This unique property of the beta-1,3-glucans has made it possible to utilize these polysaccharides as potential carriers for various functional polynucleotides. In particular, cell-uptake efficiency of the resultant polysaccharide/polynucleotide complexes was remarkably enhanced when functional groups recognized in a biological system were introduced as pendent groups. The beta-1,3-glucans can also interact with various one-dimensional architectures, such as single-walled carbon nanotubes, to produce unique nanocomposites, in which the single-walled carbon nanotubes are entrapped within the helical superstructure of beta-1,3-glucans. Various conductive polymers and gold nanoparticles are also entrapped within the helical superstructure in a similar manner. In addition, diacetylene monomers entrapped within the helical superstructure can be photo-polymerized to afford the corresponding poly(diacetylene)-nanofibers with a uniform diameter. These findings indicate that the beta-1,3-glucans are very attractive and useful materials not only in biotechnology but also in nanotechnology. These unique properties of the beta-1,3-glucans undoubtedly originate from their inherent, very strong helix-forming character which has never been observed for other polysaccharides.     

Synthesis and properties of novel fluoroalkyl end‐capped oligomers having adamantane units in the main chains via a radical process

Fluoroalkanoyl peroxides were reacted with adamantane in the presence of radical polymerizable monomers such as acrylic acid, acryloylmorpholine, and N,N‐dimethylacrylamide to afford fluoroalkyl end‐capped oligomers having adamantane units in the main chains via a radical process under very mild conditions. Thermal stability of these new fluorinated adamantane co‐oligomers thus obtained became higher than that of the corresponding fluorinated homo‐oligomers having no adamantane units. Interestingly, these fluorinated adamantane co‐oligomers exhibited good solubility in traditional organic solvents such as methanol, ethanol, tetrahydrofuran, chloroform, benzene, dimethylsulfoxide and N,N‐dimethylformamide including water, although the parent adamantane exhibited no solubility in water, methanol and dimethylsulfoxide. Furthermore, these adamantane co‐oligomers were able to reduce the surface tension effectively to form the nanometer size‐controlled self‐assembled fluorinated molecular aggregates. Copyright © 2005 John Wiley & Sons, Ltd.     

γ-irradiation of polypropylene in vacuum and in air

Polypropylene films were irradiated with ⁶⁰Co γ-rays in vacuum or in air and stored in air. Just after irradiation, the concentration of carbonyl group of the sample irradiated in air only increased with dose. The concentrations of both samples increased with storage time. The more the absorbed doses, the higher the increasing rates. The increasing rate of the concentration of carbonyl group during irradiation in air was higher than those during storage in air. Just after irradiation, the tensile strengths and the elongations of the both samples somewhat increased with dose at the doses less than 5 Mrad, but decreased at doses more than 13 Mrad. The tensile strength and the elongation of the sample irradiated in air decreased with storage time. Those of the sample irradiated in vacuum also decreased with storage time but the decreasing rates were much smaller than those in the sample irradiated in air. The gel fractions of the samples irradiated in vacuum and annealed in vacuum were somewhat higher than those irradiated in vacuum and not annealed. To elucidate high oxidation rate in the sample irradiated in air during and after irradiation, reaction mechanisms were discussed. To clarify the difference of mechanical properties between the samples irradiated in vacuum and in air, the effect of crosslink was considered, together with the oxidation.     

Effect of TRX-liposomes size on their prolonged circulation in rats

Newly formulated cationic liposomes (TRX-liposomes) with four different mean diameters were injected into twelve male rats via the lateral tail vein in order to evaluate the effect of liposomal size on pharmacokinetic parameters. TRX-liposomes disappeared from the blood according to the one-compartment model and demonstrated maximum and minimum half-lives of ca. 14 h (mean diameter of 114.3 nm) and ca. 5 h (mean diameter of 285.9 nm), respectively. This prolonged half-life tended to decrease at the boundary of 114.3 nm mean diameter. The optimal size (114.3 nm) for prolonged circulation of TRX-liposomes was consistent with that of pegylated liposomes such as Doxil((R)), however, the half-life was different among these liposomes. The electric charge of the TRX-liposomal surface is assumed to be responsible for this difference. The results of the present study will be very useful in the design of long-circulating cationic liposomes.     

Finding of remarkable synergistic effect on the aroxyl-radical-scavenging rates under the coexistence of α-tocopherol and catechins

Measurements of aroxyl radical (ArO^•)-scavenging rate constants () of antioxidants (AOHs) (α-tocopherol (α-TocH) and three catechins (CatHs) (ie, epicatechin (EC), epigallocatechin (EGC), and epigallocatechin gallate (EGCG)) were performed in ethanol solution, using stopped-flow spectrophotometry. values were measured not only for each AOH, but also for the mixtures of two AOHs (α-TocH and CatH). A notable synergistic effect that the value of α-TocH increases 1.29, 1.84, and 1.65 times under the coexistence of constant concentrations of EC, EGC, and EGCG, respectively, was observed for the solutions including α-TocH and CatH. Similarly, values of CatHs (EC, EGC, and EGCG) increased 1.72, 2.25, and 2.34 times under the coexistence of constant concentrations of α-TocH, respectively. UV-Vis absorption of α-tocopheroxyl radical (α-Toc^•) (λ_max = 428 nm), which had been produced by reaction of α-TocH with ArO^•, decreased remarkably under the coexistence of α-TocH and CatHs due to the fast α-TocH-regeneration reaction by CatHs. The result suggests that the prooxidant reaction due to α-Toc^• is suppressed by the coexistence of CatHs. By analyzing the formation and decay curves of α-Toc^•, it has been ascertained that one molecule of EGCG having three OH groups at B-ring may rapidly regenerate three molecules of α-Toc^• to α-TocH.     

2,6-Diphenylbenzo[1,2-b:4,5-b']dichalcogenophenes: a new class of high-performance semiconductors for organic field-effect transistors

2,6-Diphenylbenzo[1,2-b:4,5-b']dichalcogenophenes including thiophene, selenophene, and tellurophene analogues as organic semiconductors for field-effect transistors were effectively synthesized in three steps from commercially available 1,4-dibromobenzene. All three benzodichalcogenophenes acted as good p-type semiconductors, and particularly the selenophene analogue, 2,6-diphenylbenzo[1,2-b:4,5-b']diselenophene, showed high FET mobility of 0.17 cm2 V-1 s-1.     

Analysis of conjugated linoleic acids as 9-anthrylmethyl esters by reversed-phase high-performance liquid chromatography with fluorescence detection

A simple and highly sensitive method for determining the fatty acid composition of food lipids containing conjugated linoleic acid (CLA) is described. The method is based on the separation of the 9-anthrylmethyl ester derivatives of saturated and unsaturated (conjugated and non-conjugated) fatty acids by reversed-phase high-performance liquid chromatography with fluorescence detection. Just like the other fatty acids, CLA reacts readily with 9-anthryldiazomethane at room temperature to produce 9-anthrylmethyl esters without isomerization and decomposition of the conjugated double bonds. Clear resolution of the individual fatty acids as their 9-anthrylmethyl esters is achieved on a highly efficient octadecylsilylated silica column (150- x 3-mm i.d., 3-microm particle size) using a stepwise gradient elution with methanol-water. The method is standardized with commercially available CLA isomers (cis-9, trans-11 and trans-10, cis-12-octadecadienoic acids, and their cis,cis and trans,trans isomers) and applied for determination of the fatty acid compositions of milk and sdairy products.     

Ozonolysis of five-membered heterocycles

The relative reaction rate of five-membered heterocycles with ozone was evaluated. These relative rates were correlated to the highest bond order value in the corresponding ring, calculated by the convenient HMO method. From this correlation, the reactivity of heterocycles with ozone was able to be predicted. Also it was concluded that the predominant product in the ozonolysis of five-membered heterocycles containing an oxygen atom was the corresponding carboxylic acid, while nitrogen heterocycles gave the corresponding amide.     

High-molecular-weight poly(p-phenyleneterephthalamide) by the direct polycondensation reaction with triphenyl phosphite

Poly(p-phenyleneterephthalamide) of high molecular weight was obtained when the polycondensation of terephthalic acid and p-phenylenediamine was carried out in N-methylpyrrolidone (NMP) that contained dissolved CaCl₂ and LiCl in the presence of pyridine. The molecular weight of the polymer obtained varied with the amount of pyridine relative to the metal salts and with the molar ratios of CaCl₂ to LiCl, the maximum η_inh value of 4.5 being obtained under the conditions Py/(CaCl₂ + LiCl) ≈ 2.5 (mol/mol), CaCl₂/LiCl ≈ 1.2 (mol/mol), and LiCl + CaCl₂ ≈ 4 g. Among the solvents tested, NMP was significantly effective for the reaction. Polycondensations of several combinations of other dicarboxylic acids and diamines were carried out with limited success.