Highly selective recognition of adenine nucleobases by synthetic hosts with a linked five-six-five-membered triheteroaromatic structure and the application to potentiometric sensing of the adenine nucleotide

A new structure for an adenine-selective host molecule, featuring the pertinent link of five-six-five-membered heteroaromatic rings and two carbamoyl NH sites, was developed. This structure provides a correctly oriented array of complementary hydrogen bonding sites for the adenine nucleobase, which exploits both Watson-Crick and Hoogsteen-type interactions. The complexation with adenine nucleobases by multiple hydrogen bonding was supported by (1)H NMR spectroscopy. This type of host displayed high selectivity in complexation, with an accompanying fluorescent response to lipophilized adenosine in CHCl(3). Furthermore, a remarkably selective potentiometric response was attained for adenosine 5'-monophosphate over 5'-GMP, 5'-CMP, and 5'-UMP by using an ion-selective electrode with a PVC-supported solvent polymeric membrane. This indicates recognition of water-soluble nucleotide guests through the membrane-water interface. These findings are expected to form a reliable basis for the development of artificial sensing systems for mononucleotides in biological systems.     

Redox-driven transport of copper ions in an emulsion liquid membrane system

A new redox-driven type of emulsion liquid membrane separation is described. Milligram amounts of copper(II) in 0.2 M hydrochloric acid were reduced to copper(I) in the presence of ascorbic acid (1 M≡1 mol l⁻¹). The copper solution was emulsified with a (1+4) mixture of toluene and n-heptane using Span-80 (sorbitan monooleate) as an emusifier. The resulting water-in-oil emulsion was dispersed in 0.2 M hydrochloric acid containing hydrogen peroxide and neocuproine (2,9-dimethyl-1,10-phenanthroline) by stirring for 10 min. The copper in the internal aqueous phase was selectively transported to the external one, leaving other heavy metals (e.g., Mn, Co, Ni, Cd and Pb) in the internal aqueous phase. After collecting the dispersed emulsion globules, they were demulsified by heating and the metals in the segregated aqueous phase were determined by graphite-furnace atomic absorption spectrometry (GFAAS). The selective transport of copper offered the multielement separation of trace heavy metals from a copper matrix, allowing the GFAAS determination of impurities at the 0.01% level in copper metal.     

The survival of inefficient and efficient norms: Equilibria with and without meta-norms in a repeated norm enforcing game

ABSTRACT

Although meta-norms have been considered as the key to sustaining cooperation norms, this study argues that the meta-norms also facilitate the survival of inefficient norms. The opportunistic norm violation strategy is proposed as an alternative mechanism to motivate costly punishments. A repeated norm enforcing game, in which the externality of the normative action can be negative or positive, is analyzed. This game is equivalent to a social dilemma if the externality is large enough. The ranges of externalities that support tit-for-tat, meta-norm, and opportunism equilibria are compared. The meta-norm equilibrium has the highest stability; however, it can persist in negative externalities. Finally, the opportunism equilibrium is more stable than the tit-for-tat equilibrium, but it breaks down when the externality is small.     

Theoretical Considerations about Near-Wall Turbulence and Resulting Flow Control Schemes

Based on analytical considerations about how near-wall turbulence needs to be modified in order to reduce the momentum loss towards solid walls and to yield lower energy losses, a mechanism of turbulent drag reduction is proposed. This mechanism suggests that drag reducing flow control at high Reynolds numbers should be designed to minimize the turbulent dissipation rate. A previously published approach on how a reduction of the turbulent dissipation in the near-wall region can be achieved is analyzed further. The obtained results provide some new insight on the parameters that need to be considered when designing flow control schemes for skin friction drag reduction. (© 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)     

Quantitative analysis of the temperature effect on the radiation crosslinking and scission of polyethylene macromolecules

The γ-radiation-induced crosslinking of low-density polyethylene over a wide temperature range was studied with a new log–logarithmic scale method for sol–gel analysis. A straight line was always obtained for the plotting of log (sol fraction) against log (dose). Gel points were accurately obtained from the plot intersects, and scission/crosslinking ratios were obtained from the plot slopes via computer simulations with GelSim6 software. The crosslinking and scission yields were determined to be 0.17 and 0.078 mmol/kJ, respectively, at 30 °C, and they increased to 2.3 and 4.4 mmol/kJ, respectively, at 300 °C. The observed regularities are explained by the fact that enhanced macromolecular motion decreases the cage effect on recombination reactions in the polymer. © 2001 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 39: 1656–1661, 2001     

Large stabilization of a DNA duplex by the deoxyadenosine derivatives tethering an aromatic hydrocarbon group

Novel deoxyadenosine derivatives tethering a phenyl or naphthyl group by means of an amido linker have been synthesized, and these derivatives, stacking on the 5' end of a DNA duplex, provide free energy contributions equal to or greater than that of the Watson-Crick A/T base pair.     

Novel drug delivery device using silicone: controlled release of insoluble drugs or two kinds of water-soluble drugs

Drug release mechanism from silicone carrier differs depending on physicochemical properties of the drug. So far, there have been few reports on controlled release of insoluble drug and on simultaneous release of two kinds of water-soluble drugs. The purposes of this study are to establish methods for (1). continuous release of insoluble drug, and (2). release of two kinds of water-soluble drugs from silicone carrier. Polystyrene beads (PSTB) and proteins such as interferon (IFN) and human serum albumin (HSA) were used as model drugs. PSTB was released from silicone only when citric acid (CA) and sodium bicarbonate (SB) existed as additives. The release patterns of IFN and HSA were almost same in the case of matrix and covered-rod formulations, but double-layered formulation released them in different patterns. As far as we are aware, this is the first report on the release of insoluble drug from silicone and the controlled release of two kinds of water-soluble drugs.     

Copper complex catalyzed asymmetric monosulfonylation of meso-vic-diols

Asymmetric desymmetrization of meso-vic-diols was performed by tosylation in the presence of copper(II) triflate and (R,R)-Ph-BOX as a catalyst. The method was successfully applied to asymmetric desymmetrization of cyclic and acyclic meso-vic-diols in high enantioselectivity with up to >99% ee.