Sequence-selective DNA detection using multiple laminar streams: a novel microfluidic analysis method

On-site detection methods for DNA have been demanded in the pathophysiology field. Such analysis requires a simple and accurate method, rather than high-throughput. This report describes a novel microfluidic analysis method and its application for simple sequence-selective DNA detection. The method uses a microchannel device with a serpentine structure. Sequence-specific binding of probe DNA can be detected at one side of the microchannel. This method is capable of sequence-specific detection of DNA with high accuracy. Single base mutations can also be analyzed. Combination of laminar stream and laminar secondary flow in the microchannel enable specific detection of probe-bound DNA.     

Analysis of thiamine in dried yeast by high-performance liquid chromatography and high-performance liquid chromatography/atmospheric pressure chemical ionization-mass spectrometry

Summary High-performance liquid chromatography (HPLC) and high-performance liquid chromatography/atmospheric pressure chemical ionization-mass spectrometry (HPLC/APCI-MS) have been applied to the analysis of thiamine in dried yeast. Thiamine was extracted from dried yeast with isobutanol containing sodium 1-octanesulfonate as an ion-pairing agent and determined by HPLC on a reversed phase ODS column with UV detection at 254 nm. Response was linear in the range 25–300 μg/g of thiamine in dried yeast with a coefficient of variation in the reproducibility of 8.0%. Thiamine was recovered in good yield (109.2%, n=5). Identification of the thiamine peak was obtained by the mass spectrum using the HPLC/APCI-MS system. The utility of the selected ion monitoring technique using the HPLC/APCI-MS was also investigated. The results obtained by this method are in good agreement with those obtained by the thiochrome method [1].     

Syntheses and spectral properties of 2,3,7,8-tetracyano-5,10-dihydrodipyrazino[2,3-b:2′,3′-e]pyrazine

Base catalized intermolecular cyclization of 2-amino-3-chloro-5,6-dicyanopyrazines gave 5,10-disubsti-tuted-2,3,7,8-tetracyano-5,10-dihydrodipyrazino[2,3-b:2′,3′-c]pyrazines 11–20. These compounds have rather small molecular size but have strong intramolecular charge-transfer chromophoric system. They have strong fluorescence in solution and some have fluorescence even in the solid state which are very important to evaluate their electroluminescence property as an emitter for electroluminescence devices. The physical, structural, and electronic properties of these new 2,3,7,8-tetracyano-5,10-dihy-drodipyrazino[2,3-b:2′3′-e]pyrazines were studied using uv-visible spectroscopy and the Pariser-Parr-Pople molecular orbital calculation method.     

Controllable polymerization of N-carboxy anhydrides in a microreaction system

We have developed a microfluidic system for polymerization of amino acid N-carboxyanhydride and compared the properties of the products with those obtained by batchwise system under various experimental conditions. It was found that the microreactor produced polymers with narrower molecular weight distribution compared with polymers obtained by the batchwise system. Also, the molecular mass of the polymer produced using the microreactor was simply governed by the flow (pumping) rate. These results indicated that the microreactor could be a model for synthesis of amino acid polymer with highly controllable average molecular weight and molecular weight distribution.     

First isolation and characterization of an anti-apicophilic spirophosphorane bearing an oxaphosphetane ring: a model for the possible reactive intermediate in the Wittig reaction

An anti-apicophilic phosphorane bearing an oxaphosphetane ring, in which the ring carbon is apical and the ring oxygen is equatorial (C-apical), has been prepared as a thermally less stable stereoisomer of a phosphorane with an ordinary equatorial carbon-apical oxygen array in the oxaphosphetane ring (O-apical). This novel C-apical phosphorane, which could be considered to be a model compound of the reactive intermediate in the Wittig reaction, was fully characterized by NMR and X-ray structural analysis. The compound was found to easily isomerize to its more stable O-apical isomer, especially in the presence of proton sources, and the latter O-apical compound was found to furnish olefin at elevated temperatures.     

Super-liquid-repellent surfaces prepared by colloidal silica nanoparticles covered with fluoroalkyl groups

A simple and easy method to prepare super-liquid-repellent surfaces is proposed. Sol-gel films were prepared by hydrolysis and condensation of alkoxysilane compounds. Both surface energy and roughness were controlled using colloidal silica particles and fluoroalkylsilane. When the fractional amounts of both colloidal silica and fluoroalkylsilane were optimized in the films, the film surface exhibited repellency to both water and oil. Finally, it was shown that the method proposed here would be applied to a simple one-pot coating for a uniform large area, and be useful for practical use.     

Relativistic Gaussian basis sets for radon through plutonium

Summary Relativistic Gaussian basis sets of neutral atoms Rn-Pu and ions Th⁺⁴, U⁺³ and Pu⁺³ in the configurations of average energies are presented. The exponent parameters of the basis sets are determined by least-squares fitting to the numerical Dirac-Fock wave functions. The total energies obtained are within 0.155 a.u. of the Dirac-Fock limits and the qualities of the basis sets are between double-zeta and triple-zeta in the valence parts. Using the exponent parameters the Breit interaction energies have been calculated by perturbation theory and the self-consistent field treatment.     

Synthesis of nylon 6–clay hybrid by montmorillonite intercalated with ϵ-caprolactam

It was found that montmorillonite was intercalated with ?-caprolactam. X-ray diffraction revealed that the chain axes of the ?-caprolactam were parallel to the montmorillonite plates. The intercalated montmorillonite was swollen by molten ?-caprolactam at 200°C. ?-Caprolactam and 6-aminocaproic acid (accelerator) were polymerized with the intercalated montmorillonite at 260°C for 6 h, yielding a nylon 6-clay hybrid. X-ray diffraction and transmission electron micrography revealed that the silicate layers of the hybrid were uniformly dispersed in the nylon 6 matrix. Mechanical properties of the hybrid were improved. The strength and the modulus of the hybrid increased compared with the previously reported nylon 6 clay-hybrid (NCH) synthesized by montmorillonite intercalated with 12-aminolauric acid. The heat distortion temperature (HDT) of the hybrid was 164°C, which was 12°C higher than that of NCH. © 1993 John Wiley & Sons, Inc.     

Multi-way PLS modeling of structure–activity data by incorporating electrostatic and lipophilic potentials on molecular surface

We devised and elaborated a surface-based three-dimensional-quantitative structure–activity relationship (3D-QSAR) method, which had been proposed in the previous study. This approach can be applied to more general case where both the electrostatic and lipophilic potentials on molecular surface simultaneously change. The 3D coordinates of all sampling points on molecular surface are projected into a 2D map by Kohonen neural network (KNN). Each node in the map is coded by the associated molecular electrostatic potential (MEP) or molecular lipophilic potential (MLP) values. The electrostatic and lipophilic KNN maps are generated for each compound and the four-way array is constructed by collecting two KNN maps of all samples. The correlation between four-way array and biological activity is examined by four-way partial least-squares (PLS). For validation, the structure–activity data of estrogen receptor antagonists was investigated. The four-way PLS model gave the high statistics at calibration and validation stages. The coefficients of the four-way PLS model back-projected on molecular surface had a reasonable 3D distribution and it was nicely consistent with active site of the estrogen receptor which was recently made clear by X-ray crystallography.     

Hydrophilic chain length dependence of the ionic amphiphilic polymer monolayer structure at the air/water interface

Detailed analysis of an interesting poly(methacrylic acid) (PMAA) brush structure in water of a diblock copolymer [(Et(2)SB(m)-b-(MMA)(n), where Et(2)SB is diethylsilacyclobutane] monolayer reported previously was performed by X-ray and neutron reflectometry and indicated that the hydrophilic layer formed with a relatively long PMAA chain is not a simple layer but is divided into two layers, that is, a "carpet"-like dense PMAA layer near the hydrophobic layer and a polyelectrolyte brush layer. The hydrophilic chain length dependence of the diblock copolymer monolayer was analyzed using m:n = 30:x polymer samples, especially of the PMAA double layer structure. With the increase in PMAA chain length in polymer samples, a carpet layer is mainly formed up to n approximately 50. With further increase in the PMAA chain length beyond n approximately 50, a well-defined brush layer appears. On the other hand, the variation in hydrophobic layer thickness with methacrylic acid unit is minimum at the critical PMAA length, that is, n approximately 50 under a constant surface pressure condition. It is strongly suggested that the two discrete layers contribute differently to surface pressure. Furthermore, from the comprehensive viewpoint, the major factor for brush formation was clarified not to be the absolute length of the PMAA chain, but the ratio of PEt(2)SB and PMAA chain length is an important factor.