Electrochemical evaluation of alternating duplex-triplex conversion effect on the anthraquinone-photoinjected hole transport through DNA duplex immobilized on a gold electrode

Amperometry was employed to characterize the anthraquinone (AQ)-photoinjected hole transport through a 20-mer oligodeoxynucleotide (ODN) duplex, as immobilized on the surface of a gold electrode, and its triplex forms converted by association with several third oligopyrimidine (OPD) short strands. While the cathodic photocurrent was observed upon irradiation at 365 nm of the AQ photosensitizer linked to the end of DNA duplex, a marked lowering of the current density was identified to occur by the triplex formation of a duplex with a given third OPD short strand. The photocurrent through the DNA duplex showed a reversible fall-rise response concomitant with alternating association-dissociation cycle of the OPD short-strand, as regulated by temperature change around the corresponding melting temperature of the DNA triplex. Both the switched photoirradiation and the thermally alternating duplex-triplex conversion could provide tools of regulating the DNA hole transport.     

Highly sensitive determination of N-acyl dihydrosphingosine using liquid chromatography-electrospray ionization mass spectrometry. Application to human hair lipids

An analytical method for highly sensitive determination of four N-acyl dihydrosphingosines (NDSs) of all ceramides (CERs) in human hair, such as N-palmitoyl dihydrosphingosine (N16DS18), N-stearoyl dihydrosphingosine (N18DS18), N-lignocerol dihydrosphingosine (N24DS18) and N-nervonoyl dihydrosphingosine (N24:1DS18), has been developed using electrospray ionization (ESI) MS connected to reversed-phase LC with selected ion monitoring (SIM). The selection of negative ESI under optimal conditions of in-source collision-induced dissociation was determined based on the simplicity of molecular-related ions and their intensities. Of all ESI-MS parameters tested, the flow of dry nitrogen gas strongly affected the sensitivity of molecular-related ions, particularly in N24DS18 and N24:1DS18, while the capillary voltage elicited significantly different effects on the signal-to-noise ratio between N16DS18/N18DS18 and N24DS18/N24:1DS18. This newly developed method to determine the NDSs is the most sensitive of all existing methods, as shown in the limits of detection and quantification being in the range of 0.06-0.29 and 0.18-0.98fmol, respectively. The linearity, precision and accuracy were all sufficient to determine the NDSs in ca. 0.1mg of a hair fiber ( approximately 1cm in length). This method has been used to characterize levels of the NDSs from the proximal root end to the distal tip of each of six hair fibers obtained from two different females. Characteristic changes were observed between both females as well as among fibers derived from each female. This method will be useful not only for clarifying the roles of the CERs in human hair but also for investigating the physiology of CERs relevant to signal transduction and cell regulation in human cells/tissues.     

Bioelectrocatalytic endpoint assays based on steady-state diffusion current at microelectrode array

Highly reproducible bioelectrocatalytic endpoint assays are described. The method is based on a complete redox conversion of a substrate to a redox mediator with a corresponding redox enzyme and an amperometric detection of the reduced mediator on a diffusionally independent microelectrode array. The current reaches a steady state within a few seconds and is proportional to the number of the integrated microelectrodes. The method has successfully been applied to histamine detection at micro-molar level and glucose detection at milli-molar level.     

On quasifree representations of infinite dimensional symplectic group

We consider an infinite dimensional generalization of metaplectic representations (Weil representations) for the (double covering of) symplectic group. Given quasifree states of an infinite dimensional CCR algebra, projective unitary representations of the infinite dimensional symplectic group are constructed via unitary implementors of Bogoliubov automorphisms. Complete classification of these representations up to quasi-equivalence is obtained.     

Intermediate-temperature embrittlement of Cu bicrystals with dispersed Fe particles

The temperature dependence of deformation and fracture behavior of orientation-controlled Cu bicrystals with dispersed Fe precipitate particles was investigated. Deformation and fracture behavior at an intermediatetemperature range showed clear aging-time dependency: With increase in aging time, grain-boundary fracture became more pronounced, although fracture strain remained practically the same. The grain-boundary character and strain rate also affected the mechanical properties: With increase in the misorientation angle between the two crystals and with decrease in strain rate, grain-boundary fracture started to occur more easily at lower temperatures associated with clearer intermediate-temperature embrittlement. These experimental results were analyzed by incorporating various phenomena such as grain-boundary sliding, dynamic precipitation, growth of grain-boundary particles, and stress relaxation induced by interfacial diffusion between grain-boundary particles and the Cu matrix.     

Development of a new matrix based on a silicone ladder polymer for ion-sensing membranes.

A silicone ladder-type polymer was successfully utilized for a matrix of an ion sensing membrane to fabricate an ion-sensitive field-effect transistor. An ion sensing membrane was readily fabricated by mixing a silicone ladder-type oligomer with a quaternary ammonium salt, casting onto the gate of the field-effect transistor, and polymerizing with heating. Since no acid catalysts were needed to prepare the ion sensing membrane, it was possible to keep the quaternary ammonium salt in the matrix without decomposition. The ion-sensitive field-effect transistor based on the silicone ladder-type polymer and the quaternary ammonium salt showed a linear response with a slope of -58.1 mV decade(-1) very close to the theoretical Nernstian response over an NO3- range between 3.0 x 10(-6) and 1.0 x 10(-1) M. The time required to reach 90% total response was within 5 s, when the NO3- concentration was changed from 1.0 x 10(-3) to 3.0 x 10(-3) M. The newly fabricated ion-sensitive field-effect transistors have kept their original sensitivity for more than half a year.     

On the Spectra of the Kink for Ferromagnetic XXZ Models

We consider the kink (infinite volume nontranslationally invariant ground states) of the ferromagnetic XXZ models on the multi-dimensional lattices. We obtained the following results: (i) The pure states satisfying the local zero energy condition are necessarily product states. (ii) The Hamiltonian in the GNS representation of the kink has no gap between the ground-state eigenvalue and the rest of the spectra.     

Heterogeneous versus Homogeneous Copper(II) Catalysis in Enantioselective Conjugate‐Addition Reactions of Boron in Water

We have developed Cu^II‐catalyzed enantioselective conjugate‐addition reactions of boron to α,β‐unsaturated carbonyl compounds and α,β,γ,δ‐unsaturated carbonyl compounds in water. In contrast to the previously reported Cu^I catalysis that required organic solvents, chiral Cu^II catalysis was found to proceed efficiently in water. Three catalyst systems have been exploited: cat. 1: Cu(OH)₂ with chiral ligand L1 ; cat. 2: Cu(OH)₂ and acetic acid with ligand L1 ; and cat. 3: Cu(OAc)₂ with ligand L1 . Whereas cat. 1 is a heterogeneous system, cat. 2 and cat. 3 are homogeneous systems. We tested 27 α,β‐unsaturated carbonyl compounds and an α,β‐unsaturated nitrile compound, including acyclic and cyclic α,β‐unsaturated ketones, acyclic and cyclic β,β‐disubstituted enones, acyclic and cyclic α,β‐unsaturated esters (including their β,β‐disubstituted forms), and acyclic α,β‐unsaturated amides (including their β,β‐disubstituted forms). We found that cat. 2 and cat. 3 showed high yields and enantioselectivities for almost all substrates. Notably, no catalysts that can tolerate all of these substrates with high yields and high enantioselectivities have been reported for the conjugate addition of boron. Heterogeneous cat. 1 also gave high yields and enantioselectivities with some substrates and also gave the highest TOF (43 200 h^?1) for an asymmetric conjugate‐addition reaction of boron. In addition, the catalyst systems were also applicable to the conjugate addition of boron to α,β,γ,δ‐unsaturated carbonyl compounds, although such reactions have previously been very limited in the literature, even in organic solvents. 1,4‐Addition products were obtained in high yields and enantioselectivities in the reactions of acyclic α,β,γ,δ‐unsaturated carbonyl compounds with diboron 2 by using cat. 1, cat. 2, or cat. 3. On the other hand, in the reactions of cyclic α,β,γ,δ‐unsaturated carbonyl compounds with compound 2 , whereas 1,4‐addition products were exclusively obtained by using cat. 2 or cat. 3, 1,6‐addition products were exclusively produced by using cat. 1. Similar unique reactivities and selectivities were also shown in the reactions of cyclic trienones. Finally, the reaction mechanisms of these unique conjugate‐addition reactions in water were investigated and we propose stereochemical models that are supported by X‐ray crystallography and MS (ESI) analysis. Although the role of water has not been completely revealed, water is expected to be effective in the activation of a borylcopper(II) intermediate and a protonation event subsequent to the nucleophilic addition step, thereby leading to overwhelmingly high catalytic turnover.     

Poly(ester imide)s possessing low coefficients of thermal expansion and low water absorption (IV): Effects of ester‐linked tetracarboxylic dianhydrides with longitudinally extended structures

A series of poly(ester imide)s (PEsIs) were prepared using longitudinally extended structures of ester‐linked tetracarboxylic dianhydrides with different numbers of aromatic rings (N_Ar = 4‐6). In the PEsIs obtained using p‐phenylenediamine (p‐PDA), a clear trend was observed: the water absorption (W_A) decreased with increasing N_Ar. In contrast, no clear decrease in the T_g with increasing N_Ar was observed for the PEsIs obtained using 4,4′‐oxydianiline (4,4′‐ODA). The PEsIs obtained using a methyl‐substituted tetracarboxylic dianhydride (N_Ar = 5) showed more suppressed W_A and higher elongation at break (ε_b) values than those of the nonsubstituted counterparts. The former result is probably closely related to the enhanced crystallinity. However, methyl substitution caused an appreciable reduction in the thermal stability. Thus, the methyl‐substituted PEsIs did not meet the V‐0 standard in the UL‐94V test, unlike the substituent‐free counterparts. The PEsI copolymer obtained using the substituent‐free tetracarboxylic dianhydride (N_Ar = 6) with p‐PDA (75 mol%) and 4,4′‐ODA (25 mol%) had excellent combined properties, ie, a very high T_g (361°C), an ultralow coefficient of thermal expansion (2.2 ppm K^?1), an extremely low coefficient of hygroscopic expansion (3.3 ppm/RH%), moderate film ductility (ε_b^max = 23%), a moderate dielectric constant (3.22), and a low tan δ (2.76 × 10^?3) at 10 GHz in 50% relative humidity. Thus, this PEsI is a promising novel dielectric substrate material for use in the next generation of high‐performance flexible printed circuit boards.     

Synthesis of 2‐Azulenyl‐1,1,4,4‐tetracyano‐3‐ferrocenyl‐1,3‐butadienes by [2+2] Cycloaddition of (Ferrocenylethynyl)azulenes with Tetracyanoethylene

1‐, 2‐, and 6‐(Ferrocenylethynyl)azulene derivatives 10 – 16 have been prepared by palladium‐catalyzed alkynylation of ethynylferrocene with the corresponding haloazulenes under Sonogashira–Hagihara conditions. Compounds 10 – 16 reacted with tetracyanoethylene (TCNE) in a [2+2] cycloaddition–cycloreversion reaction to afford the corresponding 2‐azulenyl‐1,1,4,4,‐tetracyano‐3‐ferrocenyl‐1,3‐butadiene chromophores 17 – 23 in excellent yields. The redox behavior of the novel azulene chromophores 17 – 23 was examined by using cyclic voltammetry (CV) and differential pulse voltammetry (DPV), which revealed their multistep electrochemical reduction properties. Moreover, a significant color change was observed by visible spectroscopy under electrochemical reduction conditions.