Formation of hydrotalcite in aqueous solutions and intercalation of ATP by anion exchange

The formation reaction and the intercalation of adenosine triphosphate (ATP) were studied for hydrotalcite (HT), a layered double hydroxide (LDH) of magnesium and aluminum. Hydrotalcite with nitrate ions in the interlayer (HT-NO(3)) was formed (A) by dropwise addition of a solution of magnesium and aluminum nitrates (pH ca. 3) to a sodium hydroxide solution (pH ca. 14) until the pH decreased from 14 to 10 and (B) by dropwise addition of the NaOH solution to the solution of magnesium and aluminum nitrates with pH increasing from 3 to 10. The precipitate obtained with method B was contaminated with aluminum hydroxide and the crystallinity of the product was low, possibly because aluminum hydroxide precipitates at pH 4 or 5 and remains even after HT-NO(3) forms at pH above 8. With method A, however, the precipitate was pure HT-NO(3) with increased crystallinity, since the solubility of aluminum hydroxide at pH above and around 10 is high as dissolved aluminate anions are stable in this high pH region, and there was no aluminum hydroxide contamination. The formed HT-NO(3) had a composition of [Mg(0.71)Al(0.29)(OH)(2)](NO(3))(0.29).0.58H(2)O. To intercalate ATP anions into the HT-NO(3), HT-NO(3) was dispersed in an ATP solution at pH 7. It was found that the interlayer nitrate ions were completely exchanged with ATP anions by ion exchange, and the interlayer distance expanded almost twice with a free space distance of 1.2 nm. The composition of HT-ATP was established as [Mg(0.68)Al(0.32)(OH)(2)](ATP)(0.080)0.88H(2)O. The increased distance could be explained with a calculated molecular configuration of the ATP as follows: An ATP molecule is bound to an interlayer surface with the triphosphate group, the adenosine group bends owing to its bond angles and projects into the interlayer to a height of 1 nm, and the adenosine groups aligned in the interlayer support the interlayer distance.     

Mimicking an antimicrobial peptide polymyxin B by use of cyclodextrin

Cyclodextrin derivatives prepared to mimic a membrane active antibacterial peptide polymyxin B strongly permeabilized bacterial membrane and inhibited bacterial proliferation.     

Multiplexed assay for proteins based on sequestration electrochemistry using the protein binding electroactive magnetic microbeads

The paramagnetic microbead-based electrochemical binding assay was demonstrated for detecting two kinds of protein simultaneously. The principle of this assay is based on the sequestration electrochemistry. The protein binding electroactive magnetic microbeads which are conjugated with an electroactive compound and a ligand to bind specifically with a target protein were prepared. The avidin-biotin and soybean agglutinin (SBA)-galactosamine were chosen as model protein-ligand systems. The avidin binding electroactive magnetic microbead (ABEMMb) and SBA binding electroactive magnetic microbead (SBEMMb) are constructed by biotin/thionine and galactosamine/ferrocene modified on paramagnetic microbeads. The voltammetric response for these functionalized microbeads was measured by the Nd-Fe-B magnet-incorporating carbon paste rotating disk electrode. The measurements were performed in a microliter droplet using a rotating disk electrode system. Avidin and SBA were simultaneously detected by the decrease in the current responses from the reduction of ABEMMb and SBEMMb that was caused by the binding with target proteins. The limits of detection for avidin and SBA were 4 × 10(-10) and 2 × 10(-10) M, respectively.     

Ab initio evidence for strong correlation associated with Mott proximity in iron-based superconductors

We predict that iron-based superconductors discovered near d(6) configuration (5 Fe 3d orbitals filled by 6 electrons) is located on the foot of an unexpectedly large dome of correlated electron matter centered at the Mott insulator at d(5) (namely, half filling). This is based on the many-variable variational Monte Carlo results for ab initio low-energy models derived by the downfolding. The d(5) Mott proximity extends to subsequent emergence of incoherent metals, orbital differentiations due to the Mott physics, and Hund's rule coupling, followed by antiferromagnetic quantum criticality, in quantitative accordance with available experiments.     

Development of a pressure-driven nanofluidic control system and its application to an enzymatic reaction

A novel air-pressure-based nanofluidic control system was developed and its performance was examined. We found that the flow in a 100 nm scale nanochannel on a chip (called an extended nanospace channel) could be controlled within the pressure range of 0.003–0.4 MPa, flow rate range of 0.16–21.2 pL/min, and residence time range of 24 ms–32.4 s by using the developed nanofluidic control system. Furthermore, we successfully demonstrated an enzyme reaction in which the fluorogenic substrate TokyoGreen-β-galactoside (TG-β-gal) was hydrolyzed to the fluorescein derivative TokyoGreen (TG) and β-galactose by the action of β-galactosidase enzyme as a calalyst in a Y-shaped extended nanospace channel. The parameters for the reaction kinetics, such as K _m, V _max and k _cat, were estimated for the nanofluidic reaction, and these values were compared with the results of bulk and microfluidic reactions. A comparison showed that the enzyme reaction rate in the Y-shaped extended nanospace channel increased by a factor of about two compared with the rates in the bulk and micro spaces. We thought that this nanospatial property resulted from the activated protons of water molecules in the extended nanospace. This assumption was supported by the result that the pH dependence of the maximum enzyme activity in the Y-shaped extended nanospace channel was slightly different from that in the bulk and micro spaces. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Preparation of Heteroaromatic (Aryl)iodonium Imides as I−N Bond‐Containing Hypervalent Iodine

Hypervalent iodine(III) compounds containing iodine–nitrogen bonds are very attractive amination reagents in organic synthesis. Heteroaromatic (aryl)iodonium imides containing a iodine–nitrogen bond and a hypervalent iodine(III) atom were prepared from heteroarenes, bis(sulfon)imides and (diacetoxyiodo)arenes under mild conditions. These compounds were stable under air and in organic solvents, and could be easily purified by precipitation. X‐ray crystal structure analysis indicated that the structure of N‐pivaloyl indolyl(phenyl)iodonium bis(tosyl)imides and N‐pivaloyl indolyl(2‐butoxyphenyl)iodonium bis(tosyl)imides was a dimer with a T‐shaped geometry at the iodine atom linked to an indole group and a bis(tosyl)imide by a monomer unit. Moreover, the use of substituted iodoarenes facilitated the purification of some of the heteroaromatic (aryl)iodonium imides.     

Kinetic study of all-or-none hemolysis induced by cationic amphiphilic polymethacrylates with antimicrobial activity

To gain an understanding of the toxicity of antimicrobial polymers to human cells, their hemolytic action was investigated using human red blood cells (RBCs). We examined the hemolysis induced by cationic amphiphilicmethacrylate random copolymers, which have amino ethyl sidechains as cationic units and either butyl or methyl methacrylate as hydrophobic units. The polymer with 30 mol% butyl sidechains (B30) displayed higher hemolytic toxicity than the polymer with 59 mol% methyl sidechains (M59). B30 also induced faster release of hemoglobin from RBCs than M59. A new theoretical model is proposed based on two consecutive steps to form active polymer species on the RBC membranes, which are associated to RBC lysis. This model takes the all-or-none release of hemoglobin by the rupture of RBCs into account, providing new insight into the polymer-induced hemolysis regarding how individual or collective cells respond to the polymers.     

Circulation microchannel for liquid–liquid microextraction

A new method has been developed for liquid–liquid microextraction utilizing a circulation microchannel. A glass microchemical chip having a circular shallow microchannel in contact with a surrounding deeper microchannel was fabricated by a two-step photolithographic wet-etching technique. Surface modification reagent was selectively introduced to the shallow channel by utilizing capillary force, and the surface of the shallow channel was selectively made hydrophobic. With the aid of the hydrophobic/hydrophilic surface patterning, it was possible to keep organic solvent in the circular channel while the aqueous sample solution was continuously flowing in the deep channel. As a result, concentration extraction from sample solution to stationary extractant with a nanoliter scale volume became possible. Concentration extraction has been difficult in a multiphase continuous flow. Function of the newly developed microextraction system was verified with methyl red as a test sample, and concentration extraction to reach equilibrium was successfully carried out. A novel surface modification method utilizing frozen liquid as a masking material was also developed as a reverse process to make the shallow channel hydrophilic and the deep channel hydrophobic. Visualization of circulation motion inside the circular shallow channel induced by flow in the deep channel was observed with a particle tracing method.     

Fluorimetric determination of kynurenine in human serum by high-performance liquid chromatography coupled with post-column photochemical reaction with hydrogen peroxide

A high-performance liquid chromatographic method involving post-column photochemical reaction and fluorimetric detection has been developed for the determination of kynurenine in serum. Kynurenine was separated on a column of Capcell Pak C18 (resistant to pH 10). The mobile phase consisted of 0.05 M Na2B4O7-0.1 M KH2PO4 buffer (pH 8.5)-ethanol (97:3, v/v) containing 60 mM hydrogen peroxide. The post-column reagent, containing 60% (v/v) ethanol, was mixed with the mobile phase, which was irradiated with ultraviolet light to induce fluorescence. The recovery of kynurenine was 95.9 +/- 5.0% (n = 6). The method allows the determination of as little as 2 pmol of kynurenine.     

Associated production of light gravitinos in e+e? and e?γ collisions

Light gravitino productions in association with a neutralino (selectron) in e ⁺ e ⁻ (e ⁻ γ) collisions are restudied in a scenario that the lightest supersymmetric particle is a gravitino and the produced neutralino (selectron) promptly decays into a photon (electron) and a gravitino. We explicitly give the helicity amplitudes for the production processes by using the effective goldstino interaction Lagrangian, and present the cross sections with different collision energies and mass spectra. We also examine selection efficiencies by kinematical cuts and beam polarizations for the signal and background processes, and show that the energy and angular distributions of the photon (electron) can explore the mass of the t-channel exchange particle as well as the mass of the decaying particle at a future e ⁺ e ⁻ (e ⁻ γ) collider.