Development of a zinc ion-selective luminescent lanthanide chemosensor for biological applications

Detection of chelatable zinc (Zn(2+)) in biological studies has attracted much attention recently, because chelatable Zn(2+) plays important roles in many biological systems. Lanthanide complexes (Eu(3+), Tb(3+), etc.) have excellent spectroscopic properties for biological applications, such as long luminescence lifetimes of the order of milliseconds, a large Stoke's shift of >200 nm, and high water solubility. Herein, we present the design and synthesis of a novel lanthanide sensor molecule, [Eu-7], for detecting Zn(2+). This europium (Eu(3+)) complex employs a quinolyl ligand as both a chromophore and an acceptor for Zn(2+). Upon addition of Zn(2+) to a solution of [Eu-7], the luminescence of Eu(3+) is strongly enhanced, with high selectivity for Zn(2+) over other biologically relevant metal cations. One of the important advantages of [Eu-7] is that this complex can be excited with longer excitation wavelengths (around 340 nm) as compared with previously reported Zn(2+)-sensitive luminescent lamthanide sensors, whose excitation wavelength is at too high an energy level for biological applications. The usefulness of [Eu-7] for monitoring Zn(2+) changes in living HeLa cells was confirmed. This novel Zn(2+)-selective luminescent lanthanide chemosensor [Eu-7]should be an excellent lead compound for the development of a range of novel luminescent lanthanide chemosensors for biological applications.     

Observation of electrostatically released DNA from gold electrodes with controlled threshold voltages

DNA oligo-nucleotides, localized at Au metal electrodes in aqueous solution, are found to be released when applying a negative bias voltage to the electrode. The release was confirmed by monitoring the intensity of the fluorescence of cyanine dyes (Cy3) linked to the 5' end of the DNA. The threshold voltage of the release changes depending on the kind of linker added to the DNA 3'-terminal. The amount of released DNA depends on the duration of the voltage pulse. Using this technique, we can retain DNA at Au electrodes or Au needles, and release the desired amount of DNA at a precise location in a target. The results suggest that DNA injection into living cells is possible with this method.     

On the global attractivity for a logistic equation with piecewise constant arguments

In this paper, we consider the following logistic equation with piecewise constant arguments:

     

Acid-catalyzed transformation of rubrene to indenonaphthacene and its paired interacting orbital (PIO) analysis

Treatment of rubrene (5,6,11,12-tetraphenylnaphthacene) with trifluoroacetic acid in dichloromethane gives 4b,9,10-triphenyl-4b,9-dihydroindeno[1,2,3-fg]naphthacene (1) as the sole isolable product. Paired interacting orbital (PIO) analysis indicates that the reaction is initiated by preferential attack of H⁺ at C(11) position of rubrene.     

Dispersion and Confinement Loss Control in Modified Hexagonal Photonic Crystal Fibers

This paper presents a novel technique for the control of chromatic dispersion and confinement loss in hexagonal photonic crystal fibers (H-PCFs). It is demonstrated that it is possible to obtain very low chromatic dispersion of 0 ± 0:38 ps/(nm·km) in the wavelength range of 1.41 to 1.66 μm and confinement loss of less than 0.0001 dB/km from a six ring modified H-PCF (MH-PCF). The higher order dispersion at 1.55 μm is about −0.001 ps/(nm²-km).     

Thermal and photochemical reactivity of oxygen atoms on gold nanocluster surfaces

Reduction of oxidized gold nanoclusters by exposures to foreign gases and irradiation of UV photons has been investigated using X-ray photoelectron spectroscopy. Gold nanoclusters with narrow size distributions protected by alkanethiolate ligands were deposited on a TiO₂(1 1 0) surface with dip coating. Oxygen plasma etching was used for removal of alkanethiolate ligands and oxidization of gold clusters. The oxidized gold clusters were exposed to CO, C₂H₂, C₂H₄, H₂, and hydrogen atoms. Although, C₂H₄ and H₂ did not show any indications of reduction of oxidized gold clusters, CO, C₂H₂, and hydrogen atoms reduced the oxides on gold cluster surfaces. Among them, hydrogen atoms were most effective for reduction. Irradiation of UV photons around 400 nm could also reduce the oxidized gold clusters. The photochemical reduction mechanism was proposed as follows. The photo-reduction was initiated by electronic excitation of gold clusters and oxygen atoms activated reacted with carbon atoms at the surfaces of gold clusters. Carbon species were likely absorbed in gold clusters or remained at the boundaries between gold clusters when gold clusters agglomerated during oxygen plasma exposures. As the photochemical reduction progressed, carbon atoms segregated to the surfaces of gold clusters.     

Wave propagation in saturated ground using the volume fractions

The purpose of this paper is to study the dynamic behavior of soft ground including a porous layer by considering the porosity change. In order to take the porosity change into account, the concept of the volume fraction, which has been proposed in continuum mechanics, is introduced. The constitutive equations presented by Bowen are applied to the analysis of the porous media. According to Bowen's theory, the porosity is considered as a variable called the volume fraction and has its own constitutive equation. The constitutive equation of the volume fraction has thermoelastic equation coefficients and is determined by the strains of the solid and the fluid. This means that the compressibilities of the solid and the fluid are considered. When the special condition is assumed, Bowen's theory can contain Biots's theory, which has been applied in earthquake engineering. The wave propagation in the ground including a porous layer, modeled by Bowen's theory, is studied and compared with that of Biot's theory. One-dimensional attenuation and surface amplitude are calculated. The effect of the volume fraction is discussed with respect to the compressibilities of the solid and the fluid.