Potential-modulated fluorescence spectroscopy of zwitterionic and dicationic membrane-potential-sensitive dyes at the 1,2-dichloroethane/water interface

The previously introduced technique of potential-modulated fluorescence (PMF) spectroscopy was used to study the potential-induced fluorescence change of some different dyes at the polarized 1,2-dichloroethane (DCE)/water (W) interface. A zwitterionic dye (POLARIC 488PPS) showed a PMF response similar to that for the previously studied dye (di-4-ANEPPS) with the same ionic state, and the PMF response was likewise explained by the potential-dependent reorientation of the dye at the DCE/W interface. Though a monocationic dye (POLARIC 488PM) showed no distinct PMF signal, a dicationic dye (di-2-ANEPEQ) showed two relatively weak but detectable PMF signals at lower and higher potential. It has thus been found that the ionic state of a potential-sensitive dye strongly influences the potential-induced reorientation of the dye at the interface and consequently its PMF response. These results support the reorientation/solvatochromic mechanism proposed for "slow" dyes but do not necessarily exclude the electrochromic mechanism proposed for "fast" dyes. PMF spectroscopy would provide useful information on the design of slow dyes for the measurement of the resting potential of cell membranes.     

SnCl4-mediated oxidative biaryl coupling reaction of 1-naphthol and subsequent ring closure of 2,2′-binaphthol to the dinaphthofuran framework

A simple method for the direct synthesis of 2,2′-binaphthols 2 and dinaphtho[1,2-b;2′,1′-d]furans 3 under mild conditions was developed, utilizing a biaryl coupling reaction via electron donor-acceptor complexes of 1-naphthols with SnCl₄. Heating of the complex in a sealed tube for (18-24 h) afforded the corresponding o-o coupled product 2 in excellent yield. Prolonged reaction (56-65 h) under the same conditions afforded 3 in high yield in one step. We also found that in the case of α-naphthol without substituents other than a hydroxyl group at the C-1 position, regioselective o-o coupling reaction proceeded. The products 2a, 2b and 2g should be useful as synthetic intermediates for naturally occurring 3,3′-bijuglone, 3,3′-biplumbagin and elliptinone.     

Aerosol-derived Ni(1-x)Zn(x) electrocatalysts for direct hydrazine fuel cells

This article reports the synthesis and performance of unsupported Ni(1-x)Zn(x) electrocatalysts for the oxidation of hydrazine in alkaline media. Characterization of these catalysts was achieved using XRD, SEM, and TEM to confirm phase compositions, crystal structures, and morphologies. High performance was observed for the α-Ni(0.87)Zn(0.13) and β(1)-Ni(0.50)Zn(0.50) electrocatalysts with an onset potential of -0.15 V (vs. RHE) and a mass activity of 4000-3800 A g(cat)(-1) at 0.4 V (vs. RHE), respectively. Additionally, in situ IRRAS studies were conducted to understand the mechanism of oxidation. These results demonstrate the feasibility of Ni(1-x)Zn(x) catalysts for direct hydrazine anionic fuel cells.     

Basic studies on an immunoradiometric assay system for human parathyrin (intact PTH1-84)

Two-site immunoradiometric assay for human parathyrin (PTH1-84) is specific for the intact, secreted, biologically active 84 amino peptide. This system incorporates two-different polyclonal antibodies to human intact PTH and has several technical advantages for use. This assay could detect a wide range of PTH in patients with hypo-, hyperparathyroidism, chronic renal failure and hypercalcemia with malignancy, especially distinguishing the level of human intact PTH in hypoparathyroidism from in normal.     

Novel synthesis of 5-thio-hexopyranoside: preparation of 5-thio-d- and l-glucose and 1,6-anhydro-5-thio-l- and d-altrose

Asymmetric synthesis of both d- and l-isomers of 5-thioglucose and 1,6-anhydro-5-thioaltrose are described. The key intermediates, l- and d-threose diethylacetal derivatives, were derived by chemical transformation from d-xylose or d-arabinose and by Sharpless asymmetric dihydroxylation from γ-hydroxycrotylaldehyde diethylacetal. They transformed to γ-thiiranyl diethylacetal via trans-2,3-epoxy alcohol in seven steps. Acetic acid-promoted cyclization of γ-thiiranyl diethylacetal gave 5-thiopyranoside. Removal of the protected groups under the acidic conditions afforded 5-thio-d- and l-glucose and 1,6-anhydro-5-thio-l- and d-altrose, respectively.     

Self-organization mechanism of GalnP quantum wires in (GaP) m /(lnP) m short-period binary superlattices for GalnP/AllnP multi-quantum-wire (MQWR) lasers

A mechanism for self-organization of GalnP strained quantum wires in (GaP) _m /(lnP) _m short-period binary superlattice (SPBS) is discussed. To elucidate the self-organization mechanism, GalnP/AllnP compressively strained multi-quantum-wire (CS-MQWR) lasers were fabricated, changing the superlattice monolayer numberm in (GaP) _m /(lnP) _m SPBS active layers. The self-organization occurred form>1.2, determined from transmission electron microscopy images and from the anisotropic TM/TE polarization ratio in electroluminescence, i.e. an anisotropic dipole moment.The mechanism by which quantum wire axes were selected to the direction is discussed in terms of the anisotropy in adatom diffusion between [011] and directions. To confirm this, (GaP)_1.2/(lnP)_1.2 SPBS layers were grown on GaAs (100) substrates misoriented towards the [011] direction, on which the [011] adatom diffusion is suppressed. Enhanced quantum wires self-organization by substrate misorientation was observed, showing that anisotropic diffusion played an important role.The mechanism modelling of the lateral compositional modulation is discussed considering the initial growth of films largely mismatched to bottom crystals. The lateral compositional modulation is supposed to be related to GaP wire-like nuclei induced by large strain energy in the first GaP layer growth in (GaP) _m /(lnP) _m SPBSs.GalnP/AllnP CS-MQWR lasers with lowJ _th values of 257 A cm^–2 were obtained atm=1.5.     

Combined use of two membrane-potential-sensitive dyes for determination of the Galvani potential difference across a biomimetic oil/water interface

The fluorescence behavior of anionic membrane-potential-sensitive dyes, bis-(1,3-dibutylbarbituric acid) trimethine oxonol (DiBAC₄(3)) and bis-(1,3-diethylthiobarbituric acid)trimethine oxonol (DiSBAC₂(3)), at a biomimetic 1,2-dichloroethane (DCE)/water (W) interface was studied by the mean of potential-modulated fluorescence (PMF) spectroscopy. The respective dyes gave a well-defined PMF signal due to the adsorption/desorption at the DCE/W interface. It was also found that the potentials where the two dyes gave the PMF signals were different by about 100 mV. We then attempted a combined use of the two dyes for determination of the Galvani potential difference across the DCE/W interface. When 40 μM DiBAC₄(3) and 15 μM DiSBAC₂(3) were initially added to the W phase, distinctly different spectra were obtained for different interfacial potentials. The ratio of the PMF signal intensities at 530 and 575 nm (the fluorescence maximum wavelengths for the respective dyes) showed a clear dependence on the interfacial potential. These results suggested the potential utility of the combined use of two dyes for the determination of membrane potentials in vivo.