Highly reproducible method of planar lipid bilayer reconstitution in polymethyl methacrylate microfluidic chip

We developed a highly reproducible method for planar lipid bilayer reconstitution using a microfluidic system made of a polymethyl methacrylate (PMMA) plastic substrate. Planar lipid bilayers are formed at apertures, 100 microm in diameter, by flowing lipid solution and buffer alternately into an integrated microfluidic channel. Since the amount and distribution of the lipid solution at the aperture determines the state of the lipid bilayer, controlling them precisely is crucial. We designed the geometry of the fluidic system so that a constant amount of lipid solution is distributed at the aperture. Then, the layer of lipid solution was thinned by applying an external pressure and finally became a bilayer when a pressure of 200-400 Pa was applied. The formation process can be simultaneously monitored with optical and electrical recordings. The maximum yield for bilayer formation was 90%. Using this technique, four lipid bilayers are formed simultaneously in a single chip. Finally, a channel current through gramicidin peptide ion channels was recorded to prove the compatibility of the chip with single molecule electrophysiology.     

Lateral capillary forces between solid bodies on liquid surface: a lattice Boltzmann study

When two solid bodies are placed on the surface of a dense liquid under gravitation, they deform the liquid surface to experience a lateral capillary force between themselves that can be attractive and repulsive, depending on the wettabilities and weights of the bodies. In the present study, the lateral capillary force between two square bodies at a liquid-vapor interface has been examined using numerical simulations based on a two-dimensional two-phase lattice Boltzmann (LB) method. The particular situations were simulated, where every body was vertically constrained and had the fixed triple points at its upper or lower corners. Here, the triple point indicates the place at which vapor, liquid, and solid phases meet. The interaction force between these two bodies was calculated as a function of the separation distance, the interfacial tension, and the gravitational acceleration. The simulation results agree well with the analytical expression of the lateral capillary interaction, indicating that our LB method can reproduce the interaction force between two bodies of various wettabilities at a liquid-vapor interface in mechanical equilibrium.     

A new entry to doubly N-confused [26]hexaphyrins(1.1.1.1.1.1) from normal [26]hexaphyrins(1.1.1.1.1.1) through an unprecedented double pyrrolic rearrangement

Treatment of hexakis(pentafluorophenyl)-substituted [26]hexaphyrin(1.1.1.1.1.1) (1) with CuCl in the presence of pyridine and molecular oxygen led to formation of doubly N-confused [26]hexaphyrin(1.1.1.1.1.1) 2 in a moderate yield through an unprecedented double pyrrolic rearrangement. Macrocycle 2 has been shown to serve as an effective bis-metal-coordinating ligand and exhibits attractive optical properties such as a sharp Soret-like band at 566 nm and low-energy fluorescence at 1058 nm.     

Studies of an Fe9 tridiminished icosahedron

The synthesis and structural characterization of a nonanuclear FeIII cage complex is reported. The nine iron centers in [Fe9(mu3-O)4(O3PPh)3(O2CCMe3)13] lie on the vertices of an incomplete icosahedron, with the P atoms of triphenylphosphonate at the other three vertices. The paramagnetic core therefore describes a tridiminished icosahedron. Magnetic studies suggest an S=1/2 ground state for the molecule. Analysis of exchange paths and the susceptibility data point to the interpretation that the cluster can be divided into two nearly decoupled sections: an {Fe6O3} section, with an S=0 ground state, in which three oxo-centered triangles bound a central triangle that is not oxo-centered; and an {Fe3O} triangle with S=1/2. The analysis of the susceptibility data leads to a Heisenberg model based on three significant antiferromagnetic exchange interactions, with values of 173.7 cm-1 in the {Fe3O} triangle, and 30.9 and 19.1 cm-1 within the {Fe6O3} section, while the exchange between them is <1 cm-1. With these assignments, the theoretical low-temperature differential susceptibility is also in very good agreement with measurements up to 50 T. Magnetic measurements in the milli-kelvin range reveal striking hysteresis loops and magnetization reversals associated with a Landau-Zener-Stückelberg (LZS) transition as enhanced by the occurrence of a phonon bottleneck.     

Coexistence of wave propagation and oscillation in the photosensitive Belousov-Zhabotinsky reaction on a circular route

The photosensitive Belousov-Zhabotinsky (BZ) reaction was investigated on a circular ring, which was drawn using computer software and then projected on a film soaked with BZ solution using a liquid-crystal projector. Under the initial conditions, a chemical wave propagated with a constant velocity on the black ring under a bright background. When the background was rapidly changed to dark, coexistence of the oscillation on part of the ring and propagation of the chemical wave on the other part was observed. These experimental results are discussed in relation to the nature of the photosensitive BZ reaction and theoretically reproduced based on a reaction-diffusion system using the modified Oregonator model.     

Interactive propagation of photosensitive chemical waves on two circular routes

The propagation of chemical waves in the photosensitive Belousov-Zhabotinsky (BZ) reaction was investigated using an excitable field composed of two rings in slight contact, which were drawn using computer software and then projected on a film soaked with BZ solution using a liquid-crystal projector. When the initial phase difference between the two chemical waves in the individual rings was smaller than a critical value, this initial value was maintained after collision of the chemical waves. However, when the initial phase difference was larger than this critical value, the phase difference converged to the same value after the second collision. The critical value increased with an increase in the thickness of the rings. These experimental results on the geometry of the excitable field are discussed in relation to the nature of chemical wave propagation. These results suggest that the photosensitive BZ reaction may be useful for creating spatiotemporal patterns that depend on the geometric arrangement of excitable fields.     

Stereoselective synthesis of cis- and trans-oligo(phenylenevinylene)s via palladium-catalyzed cross-coupling reactions

cis-Oligo(phenylenevinylene)s (OPVs) are synthesized by Suzuki-Miyaura coupling of arylboronic acids with (Z)-bromoalkenes in over 96% geometrical purity. On the other hand, trans-oligo(phenylenevinylene)s can be synthesized by Hiyama coupling of aryl iodide with (E)-alkenylsilanes in almost perfect purities. Effect of pi-conjugation chain length on photoisomerization behavior of OPVs is described.     

Microchip-based liquid-liquid extraction for gas-chromatography analysis of amphetamine-type stimulants in urine

A microchip-based liquid-liquid extraction for the gas chromatography analysis of urine for amphetamine-type stimulants has been developed. Partially modified microchannels with the capillarity restricted modification (CARM) method were employed for stabilizing the interface consisting of 1-chlorobutane and alkalized urine. Reliability of the microchip-based extraction was evaluated with respect to linearity, trueness and precision. As a practical demonstration, methoxyphenamine hydrochloride (50 mg) was administered to three healthy volunteers, and the concentration of methoxyphenamine in their urine was determined by both methods for comparison. This study showed the potential of pressure-driven microfluidics to contribute to the rapid automation analysis in forensic toxicology.     

Liquid phase microextraction with in situ derivatization for measurement of bisphenol A in river water sample by gas chromatography-mass spectrometry

A new method that involves liquid phase microextraction (LPME) with in situ derivatization and gas chromatography-mass spectrometry (GC-MS) is described for the determination of trace amounts of bisphenol A (BPA) in river water samples. The LPME conditions, such as the type of extraction solvent and the extraction time, are investigated. Then, the extract is directly injected into GC-MS. The detection limit and the quantification limit of BPA in river water sample are 2 and 10pgml(-1) (ppt), respectively. The calibration curve for BPA is linear with a correlation coefficient of >0.999 in the range of 10-10,000pgml(-1). The average recoveries of BPA in river water samples spiked with 100 and 1000pgml(-1) BPA are 104.1 (RSD: 8.9%) and 98.3 (RSD: 3.2%), respectively, with correction using the added surrogate standard, bisphenol A-(13)C(12). This simple, accurate, sensitive and selective analytical method may be applicable to the determination of trace amounts of BPA in liquid samples.     

Effects of cleaning procedures of silica wafers on their friction characteristics

Silicon wafers with thermal silicon oxide layers were cleaned and hydrophilized by three different methods: (1) the remote chemical analysis (RCA) wet cleaning by use of ammonia and hydrogen peroxide mixture solutions, (2) water-vapor plasma cleaning, and (3) UV/ozone combined cleaning. All procedures were found to remove effectively organic contaminations on wafers and gave identical characteristics of the contact angle, the surface roughness and the normal force interactions, measured by atomic force microscopy (AFM). However, it is found that wafers cleaned by the RCA method have several times larger friction coefficients than those cleaned by the plasma and UV/ozone methods. The difference was explained by the atomic-scale topological difference induced during the RCA cleaning. This study reveals the lateral force microscopy as a very sensitive method to detect the microstructure of surfaces.