Quenching of luminescence by coloration in KI and RbI

Quenching of exciton luminescence caused by coloration with u.v. irradiation in KI and RbI has been studied. Luminescence intensity measured after coloration is found to show a remarkable dependence on temperature. A possible explanation is given for the mechanism of luminescence quenching on the assumption that the luminescence intensity is proportional to the probability of exciton self-trapping.     

Universality of phase transitions at solid surfaces

Recent progress in theoretical and experimental studies on various order-disorder phase transitions at solid surfaces is reviewed. An emphasis is put on the problem of the universality class of surface phase transitions.     

A formal synthesis of martinelline via a combination of two types of radical reactions

A formal synthesis of martinelline has been accomplished via two types of radical reactions as the key steps. These are the radical addition-cyclization-elimination of an oxime ether carrying an unsaturated ester and a C-C bond formation through a radical 1,5-hydrogen atom translocation.     

Differential expression of phosphatidylethanol-amine-binding protein in rat hepatoma cell lines: analyses of tumor necrosis factor-alpha-resistant cKDH-8/11 and -sensitive KDH-8/YK cells by two-dimensional gel electrophoresis

To determine intracellular factors influencing the sensitivity of cancer cells to tumor necrosis factor-alpha (TNF-alpha), we studied the expression of intracellular proteins in TNF-alpha-resistant cKDH-8/11 and -sensitive KDH-8/YK rat hepatoma cell lines using the technique of two-dimensional gel electrophoresis (2-DE). From the 2-DE patterns, it was demonstrated that TNF-alpha-resistant cKDH-8/11 cells had increased levels of protein of molecular weight (Mr) 22 500 and isoelectric point (pI) 5.2, compared with TNF-alpha-sensitive KDH-8/YK cells. Therefore, we excised cyanogen bromide (CNBr) fragments of proteins in the spot for N-terminal sequencing. Microsequencing for the CNBr fragments identified the protein as rat phosphatidylethanolamine-binding protein. These findings suggest that the intracellular phosphatidylethanolamine-binding protein could be one of the factors responsible for the resistance of cKDH-8/11 cells to TNF-alpha-induced cell death.     

Development of a novel compression tester and rheo-mechanical properties of wet-mass powder. I--Effect of kneading time on the rheo-mechanical properties

In our previous paper [Watano S., et al., Chem. Phram. Bull., 49(1), 64-68, (2001)], a compaction tester was developed to quantitatively evaluate the water dispersion condition of wet kneaded masses prepared by a paddle type kneader. It was also demonstrated that the physical properties of pellets prepared by extrusion granulation after the kneading could be well predicted by the vertical pressure transmission obtained through the compaction tester. However, in this compression tester, the vertical pressure transmission was just obtained and rheological and mechanical properties (so called rheo-mechanical properties) of wet mass-powder that should be the most important to determine the deformation process were not well studied. In this study, a novel compression tester, which can measure both vertical and radial pressure transmissions, has been developed. Based on the compression test, mechanical property (Young's modulus) and rheological property (effective internal friction) of wet mass powder prepared by different kneading times were quantitatively investigated. Granules (pellets) were then obtained through the extrusion granulation and fluidized bed drying, and the physical properties (strength and disintegration time) of the obtained pellet were evaluated. The relationship between the granule (pellet) physical properties and the mechanical and rheological (rheo-mechanical) properties was analyzed.     

Selective dissociation of non-covalent bonds in biological molecules by laser spray

The laser spray developed in our laboratory was applied to the analysis of bovine serum albumin (BSA), double-stranded DNA (dsDNA) and a protein-DNA complex. The tip of a stainless-steel capillary was irradiated with a 10.6 micro m infrared laser by increasing the laser power from 0 W (electrospray) to 1.4 W. The laser beam was focused to about 0.3 mm at the tip of the stainless-steel capillary. When BSA aqueous solution was irradiated by the laser, highly charged monomer ions were newly observed in addition to the multiply charged ions of non-denatured monomer, dimer and trimer moieties. This indicates that BSA suffers from denaturation on irradiation with an infrared laser in solution. A 1.4 W laser power is not sufficient to cause the complete denaturation of BSA under the present experimental conditions. Whereas dsDNA was found to dissociate almost completely to single-stranded DNA constituents on laser irradiation with a power of 1.2 W, no fragmentation of DNA molecules was observed. For a protein-DNA complex, i.e. a complex of c-Myb DNA binding domain and dsDNA, dissociation of the complex to the component moieties was observed. These findings indicate that the laser spray can selectively dissociate non-covalent complexes into subunits without causing dissociation of the covalent bonds of the subunits. The laser spray will be a versatile method for the investigation of the structures and stabilities of biomolecules including non-covalent complexes.     

Extraction mechanism of Cr(VI) on the aqueous two-phase system of tetrabutylammonium bromide and (NH(4))(2)SO(4) mixture

An aqueous two-phase system of tetrabutylammonium bromide (TBAB) and (NH(4))(2)SO(4) mixture has been developed for the extractive preconcentration and separation of certain compounds. TBAB concentration in upper phase is much higher than that of bottom solution. This new aqueous two-phase system is proposed for the highly selective extraction of Cr(VI) from large amounts of Cr(3+). The Cr(VI) is found to be extracted into the TBAB-rich upper phase due to ion pair formation such as HCrO(4)(-) . TBAB(+). The Cr(VI) was sufficiently extracted into the upper phase in the pH range from 1 to 5. The proposed method has been applied to the determination of trace of Cr(VI) in wastewater samples with a coefficient of variation less than 3.2%. The recovery obtained was not lower than 90%. The determination limit for the Cr(VI) was found to be 60 mug l(-1) in 10 ml of sample solution.     

Two-step laser excitation fluorescence study of the magnetic field effect on the hydrogen abstraction reaction of anthraquinone in SDS micellar solution

The magnetic field effect on the hydrogen abstraction reaction of anthraquinone in sodium dodecyl sulfate (SDS) micellar solution has been studied by two-step laser excitation fluorescence including a variable delay technique. The risetime of the “cage product” is 380 ns at 0 G and 890 ns at 800 G, while its yield decreases by 20% at 800 G. The results are interpreted in terms of the radical pair model of CIDNP.     

Mechanism of reduction of nitrogen oxides with propene in excess oxygen catalyzed by bifunctional catalysts

HC-SCR (selective reduction of nitrogen oxide by hydrocarbon) and our view on its reaction mechanism are briefly described, and then our attempts in the last few years to design catalysts based on the concept of bifunctional catalysis for HC-SCR are reviewed. The example chosen is the NO-C₃H₆-O₂-H₂O reaction catalyzed by mechanical mixtures of transition metal oxides (e.g., Mn₂O₃) and metal-loaded ZSM-5 zeolites. The synergistic effect of two components was explained based on a reaction mechanism comprising NO oxidation, oxidative decomposition of the products of NO₂-C₃H₆ reactions and polymerization of (or carbon deposition from) C₃H₆.     

Design of Dual‐Emission Chemosensors for Ratiometric Detection of ATP Derivatives

Nucleoside pyrophosphate (nucleoside PP) derivatives are widespread in living cells and play pivotal roles in various biological events. We report novel fluorescence chemosensors for nucleoside PPs that make use of coordination chemistry. The chemosensors, which contain two Zn^II–dipicolylamine units, bind strongly to nucleoside PPs (K_app>10⁶ M ^?1) in aqueous solution and sense them by a dual‐emission change. Detailed fluorescence and UV/Vis spectral studies revealed that the emission changes of the chemosensors upon binding to nucleoside PPs can be ascribed to the loss of coordination between Zn^II and the acridine fluorophore. This is a unique sensing system based on the anion‐induced rearrangement of the coordination. Furthermore, we demonstrated the utility of these chemosensors in real‐time monitoring of two important biological processes involving nucleoside PP conversion: the apyrase‐catalyzed hydrolysis of nucleoside PPs and the glycosyl transfer catalyzed by β‐1,4‐galactosyltransferase.