Novel synthesis, static and dynamic properties, and structural characteristics of 5-cyano[n](2,4)pyridinophane-6-ones (n= 9-6) and their chemical transformations

A novel synthesis of 5-cyano[n](2,4)pyridinophane-6-ones 12a-d (n= 9, 8, 7, and 6) consists of allowing cyanoacetatoamide to react with cycloalk-2-enones. Their static and dynamic properties as well as structural characteristics are studied on the basis of their spectroscopic properties, cyclic voltammetry, and theoretical calculations. The (1)H and (13)C NMR spectra at various temperatures have clarified the dynamic behavior of the methylene chains for [7](2,4)- and [6](2,4)pyridinophane-6-one derivatives 12c and 12d. The energy barrier (Delta G(++)) of the bridge flipping of 12c is estimated to be 12.0 kcal mol(-1)(T(c)= 0 degree C). On the other hand, compound 12d undergoes pseudorotation (conformational change of the methylene chain) at room temperature, and does not undergo bridge flipping even at 150 degree C in DMSO-d(6). The energy barrier (Delta G(++)) of the pseudorotation of the methylene chain 12d of is found to be 10.5 kcal mol(-1)(T(c)=-25 degree C), and thus, two stable conformers of the hexamethylene bridge of 12d are determined as predicted by theoretical calculations. Deformation of the pyridone ring of 12d is also determined by X-ray crystallographic analysis. Furthermore, chemical transformations of 12a-c leading to 5-carbamoyl[n](2,4)pyridinophanes 15a-c are also accomplished successfully in moderate to good yields.     

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.     

Inclusion of cut and as-grown single-walled carbon nanotubes in the helical superstructure of schizophyllan and curdlan (beta-1,3-glucans)

We have found that single-chain schizophyllan and curdlan (s-SPG and s-curdlan, respectively) can dissolve as-grown and cut single-walled carbon nanotubes (ag-SWNTs and c-SWNTs, respectively) in aqueous solution. The vis-NIR spectra of the composites suggest that c-SWNTs are dissolved as a bundle, whereas ag-SWNTs exist as one or only a few pieces in the tubular hollow constructed by the helical structure inherent to these beta-1,3-glucans. EDX and CLSM measurements and TEM observation established that the distribution map of these polysaccharides overlaps well with the image of SWNTs, indicating that these two components form a composite. Very interestingly, when c-SWNTs were dissolved with the aid of s-SPG or s-curdlan in water, a clear periodical structure with inclined stripes, as detected by AFM, appeared on the fibrous composite surface. Because this periodical structure has never been recognized for the composites with other water-soluble polymers, one can regard that s-SPG or s-curdlan wraps c-SWNTs constructing a helically twined structure. High-resolution TEM observation of an ag-SWNTs/s-SPG composite gave a clearer image in that two s-SPG chains twine one ag-SWNT and the helical motif is right-handed. When this sample was subjected to the AFM measurement, the composite showed the 2-3 nm height. This height implies that one piece of ag-SWNT is included in the s-SPGs helical structure. As a summary, it has been established that beta-1,3-glucans such as s-SPG and s-curdlan not only dissolve SWNTs but also create a novel superstructure on the surface.     

Photocatalytic Reduction of NO with C2H6 on a Hollandite-Type Catalyst

The photocatalytic reduction of nitrogen monoxide (NO) with ethane on the hollandite type catalyst (K₂Ga₂Sn₆O₁₆KGSO) was investigated. Using a closed-gas circulating system equipped with a Q-MASS detector and in-situ diffuse reflectance FT-IR spectroscopy. The reactant gases of NO and ¹³C₂H₆ decreased with the increasing irradiation time. In contrast, the N₂ yield increased proportionally to the conversion of ¹³C₂H₆. Nitrogen oxides such as N₂O did not reach their detectable levels. The NO adsorbed on KGSO was found to change to its activated species by UV irradiation. The oxidized products of C₂H₆ such as CH₃CHO increased in proportion to the reaction time. The present results strongly suggest that KGSO has remarkable photocatalytic activity for the reduction of NO with C₂H₆.     

Flame atomic absorption spectrometric determination of lead in waste water and effluent after preconcentration using a rapid coprecipitation technique with gallium phosphate

A determination method for lead in waste water and effluent was studied using flame atomic absorption spectrometry after preconcentration of lead by the rapid coprecipitation technique with gallium phosphate. Lead ranging from 0.5 to 50 μg was quantitatively coprecipitated with gallium phosphate from 100–150 mL sample solution (pH ∼5). The presence of gallium phosphate did not affect the atomic absorbance of lead. Since the concentration of gallium in the final sample solution is also measurable by flame atomic absorption spectrometry at 250.0 nm without further dilution, the rapid coprecipitation technique, which does not require complete collection of the precipitate, becomes possible using a known amount of gallium and measuring the concentrations of both lead and gallium in the final sample solution by flame atomic absorption spectrometry. The 32 diverse ions tested gave no significant interferences in the lead determination. The method proposed here is rapid and has good reproducibility. Received: 16 August 1999 / Revised: 6 October 1999 / Accepted: 14 October 1999     

Giant motion of La atom inside C82 cage

An anomalous charge density distribution of La atom encapsulated in a C₈₂ cage has been revealed for La@C₈₂ by the maximum entropy method (MEM)/Rietveld analysis using synchrotron powder diffraction data. The obtained La atom charge density shows a feature almost like a bowl or a hemisphere, suggesting that the La atom has a giant motion (large amplitude motion) inside the C₈₂ cage at room temperature. From the obtained MEM charge density, the main results are (1) the cage structure of La@C₈₂ (I) has C_2V symmetry; (2) La atom locates at an off-centered position adjacent to a six-membered ring of the carbon cage; (3) the nearest La–C distance is 2.55(8) and (4) the amount of charge transfer from the La atom to the carbon cage is about 3.2 e, which corresponds to the nominal electronic structure, La³⁺@C₈₂³⁻.     

A new biisoflavonoid from the roots of Erythrina variegata

A new biisoflavonoid, biseryvarin A (1a), together with two known compounds were isolated from the roots of Erythrina variegata. The structure of biseryvarin A was established on the basis of spectroscopic evidence. Biseryvarin A is the first dimeric isoflavonoid possessing isoprenoid groups from the genus Erythrina. Biseryvarin A showed low activity against methicillin-resistant Staphylococcus aureus (MRSA).     

Automated on-line in-tube solid-phase microextraction coupled with HPLC/MS/MS for the determination of butyrophenone derivatives in human plasma

This paper describes a fully automated on-line method combining in-tube solid-phase microextraction (SPME) in which sample clean-up and enrichment are conducted through an open tubular fused-silica capillary column and high-performance liquid chromatography (HPLC)/tandem mass spectrometry (MS/MS) detection for the determination of six butyrophenone derivatives (moperone, floropipamide, haloperidol, spiroperidol, bromperidol, and pimozide) in human plasma samples. The six butyrophenones were extracted by repeatedly aspirating and dispensing plasma sample solutions on a DB-17 capillary column (60 cm × 0.32 mm i.d., film thickness 0.25 μm). The analytes retained on the inner surface of the capillary column were then eluted into an acetonitrile-rich mobile phase using a gradient separation technique. Extraction efficiencies ranged from 12.7% to 31.8% for moperone, spiroperidol, and pimozide, and from 1.08% to 4.86% for floropipamide, haloperidol, and bromperidol. The regression equations for all compounds showed excellent linearity, ranging from 0.05 to 50 ng/0.1 mL of plasma, except for moperone and spiroperidol (0.01 to 50 ng/0.1 mL). The limits of detection and quantification in plasma for each drug were 0.03–0.2 and 0.1–0.5 ng/mL, respectively. The intra- and inter-day coefficients of variation for all compounds in plasma were not greater than 13.7%.     

Behavior of a polymer chain immersed in a binary mixture of solvents

The behavior of a polymer chain immersed in a binary solvent mixture is investigated via a single-polymer simulation using an effective Hamiltonian, where the solvent effects are taken into account through a density-functional theory for polymer-solvent admixtures. The liquid-liquid phase separation of the binary solvent mixture is modeled as that of a Lennard-Jones binary fluid mixture with weakly attractive interactions between the different components. Two types of energetic preferences of the polymer chain for the better solvent-(A) no preferential solvophilicity and (B) strong preferential solvophilicity-are employed as polymer-solvent interaction models. The radius of gyration and the polymer-solvent radial distribution functions are determined from the simulations of various molar fractions along an isotherm slightly above the critical temperature of the liquid-liquid phase separation. These quantities near the critical point conspicuously depend on the strength of the preferential solvophilicity. In the case where the polymer exhibits a strong preferential solvophilicity, a remarkable expansion of the polymer chain is observed near the critical point. On the other hand, in the case where the polymer has no preferential solvophilicity, no characteristic variation of the polymer conformation is observed even near the critical point. These results indicate that the expansion of a polymer chain enhances the local phase separation around it, acting as a nucleus of demixing in the vicinity of the critical point. This phenomenon in binary solvents near the liquid-liquid critical point is similar to the expansion of the polymer chain in one-component supercritical solvents near the liquid-vapor critical point, which we have reported [T. Sumi and H. Sekino J. Chem. Phys. 122, 194910 (2005)].