Visible light photoelectrochemical activity of K4Nb6O17 intercalated with photoactive complexes by electrostatic self-assembly deposition

Electrostatic self-assembly deposition (ESD) results in the intercalation of Ru(bpy)₃²⁺ or methylene blue (MB) into the niobate layered oxide right after the cations come into contact with [Nb₆O₁₇]⁴⁻ nanosheets. Monolayers can be obtained by the exfoliation of proton exchanged K₄Nb₆O₁₇ (KNbO) in an aqueous tetrabutylammonium (TBA) solution as revealed by the atomic force microscopy micrographs. UV-vis spectra show that intercalated films are able to absorb in the visible light range. Heat-treatment of Ru(bpy)₃²⁺ resulted in the red-shift in the absorption spectra, which was assigned to the enhancement in the interaction between the complex molecules and [Nb₆O₁₇]⁴⁻ host layer. Intercalated niobate layered oxides are able to produce photocurrent as a result of the electron transfer from the excited guest molecule to the host layer under visible light illumination. Ru(bpy)₃²⁺ intercalated niobate layered oxide shows photocatalytic activity under visible light illumination to produce H₂ from water-methanol solution.     

Synthesis and identification of an endogenous sperm activating and attracting factor isolated from eggs of the ascidian Ciona intestinalis; an example of nanomolar-level structure elucidation of novel natural compound

A sperm-activating and attracting factor (SAAF) was isolated from the eggs of the ascidian Ciona intestinalis, and its structure was deduced with only approximately 4 μg of the specimen. Based upon the proposed structure, two epimers were synthesized from chenodeoxycholic acid in 16 steps. Comparison between synthetic and natural compounds led to the unambiguous structure determination of SAAF to be (3R,4R,7R,25S)-3,4,7,26-tetrahydroxycholestane-3,26-disulfate. The synthetic pure specimen was also utilized to confirm that both sperm-activation and attraction were elicited by a single compound.     

Design and synthesis of an enzyme-cleavable sensor molecule for phosphodiesterase activity based on fluorescence resonance energy transfer

Ratiometric measurement is a technique that can provide precise data and even quantitative detection. To carry out ratiometric measurements, it is necessary that the sensor molecule exhibits a large shift in its emission or excitation spectrum after reaction with the target molecule. Fluorescence resonance energy transfer (FRET) is one mechanism used to obtain a large spectral shift. In this study, our aim was to develop a ratiometric fluorescent sensor molecule for phosphodiesterase activity based on FRET. We designed and synthesized CPF4 with a coumarin donor, a fluorescein acceptor, and two phenyl linkers having the phosphodiester moiety interposed between them. In the emission spectrum of CPF4 in aqueous buffer excited at 370 nm, the emission of the coumarin donor was strongly quenched and the emission of the fluorescein acceptor was observed. This emission spectrum demonstrates that energy transfer from the coumarin donor to the fluorescein acceptor proceeds efficiently. Addition of a phosphodiesterase to an aqueous solution of CPF4 resulted in an increase in the donor fluorescence and a decrease in the acceptor fluorescence. CPF4 exhibited a large shift in its emission spectrum after the hydrolysis of the phosphodiester group by the enzyme. This large shift of the emission spectrum indicates that ratiometric measurements can be made by using CPF4. The method described in this paper for designing enzyme-cleavable sensor molecules based on FRET should be readily applicable to other hydrolytic enzymes.     

Experimental and theoretical studies on the nature of weak nonbonded interactions between divalent selenium and halogen atoms

To investigate the nature of weak nonbonded selenium...halogen interactions (Se...X interactions; X = F, Cl, and Br), three types of model compounds [2-(CH(2)X)C(6)H(4)SeY (1-3), 3-(CH(2)X)-2-C(10)H(6)SeY (4-6), and 2-XC(6)H(4)CH(2)SeY (7-9); Y = CN, Cl, Br, SeAr, and Me] were synthesized, and their (77)Se NMR spectroscopic behaviors were analyzed in CDCl(3). The gradual upfield shifts of (77)Se NMR absorptions observed for series 1-3 and 4-6 suggested that the strength of Se...X interaction decreases in the order of Se...F > Se...Cl > Se...Br. The quantum chemical calculations at the B3LYP/631H level using the polarizable continuum model (PCM) revealed that the most stable conformer for 1-3 is the one with an intramolecular short Se...X atomic contact in CHCl(3) (epsilon = 4.9) and also that the n(X) --> sigma(Se-Y) orbital interaction (E(Se...X)) can reasonably explain the order of strength for the Se...X interactions. On the other hand, the (77)Se NMR absorptions observed for series 7-9 did not shift significantly from the reference compounds (C(6)H(5)CH(2)SeY), indicating the absence of the Se...X interaction for 7-9 presumably due to attenuation of basicity for the halogen atom that is substituted directly to the aromatic ring. These observations suggested that the n(X) --> sigma(Se-Y) orbital interaction is a dominant factor for formation of weak Se...X interactions. Electron correlation was also suggested to be important for the stability.     

Weyl's Gauge Field and Its Behavior

Using a manifestly gauge-invariant Lagrangian density of a system in which a real scalar field (matter field) is interacting with itself and with Weyl's gauge field, we shall study equations of the real scalar field and of Weyl's gauge field, and discuss the self-interacting term of the real scalar field. For a special self-interacting term, we shall obtain an equation of only Weyl's gauge field which plays an important role in solving the equation of Weyl's gauge field interacting with the real scalar field. By making use of the above mentioned equation we shall obtain a rigorous solution for Weyl's gauge field. Next, combining the equation of only Weyl's gauge field with the condition in Weyl's gauge field that the length scale of any vector changes under parallel transfer, we shall obtain a nonlinear equation for the length scale of Weyl's gauge field, which may be important in mathematical physics and is shown to have meron-type solution. By making use of the same techniques being used above, we shall study solution of equation of gradient Weyl's gauge field and as a result, obtain a nonlinear equation of the same type as being found above. Finally we shall study relation between local gauge transformation and symmetric connection in space-time. As a result, we can partly make clear relation between the change in the measure of length scale of a vector due to an infinitesimal parallel transfer and the coefficients of affine connection of Weyl's geometry.     

Synthesis and properties of TSF-based spin-polarized donor

A novel organic donor radical, TSBN, which is a benzotetraselenafulvalene derivative carrying a nitronyl nitroxide group in a cross-conjugated manner was prepared. X-ray crystallographic analysis revealed that TSBN forms a sheet-like network within the ac plane through intermolecular chalcogen contacts. Its spin-polarized structure was confirmed by cyclic voltammogram, ESR spectra of singly oxidized species and DFT calculation. The neutral crystal of TSBN showed nonlinear I–V characteristics at 2 K and exhibited negative magnetoresistance (?5% at 2 K under 5 T).     

AM1 calculation of hydration to aldehyde group in nitro-substituted benzaldehydes

Hydration to the aldehyde group in nitro-substituted benzaldehydes was studied theoretically by using an AM 1 method. The calculated values of activation energy and heat of reaction showed good correlations with the experimental values of rate constants and equilibrium constants, respectively. To examine the hydration mechanism, localized molecular orbitals were calculated. Furthermore, expression of the molecular orbitals of supermolecular complexes in terms of occupied and vacant orbitals of the component molecules elucidated that the interaction between the lonepair orbital of water and the antibonding C? O π-orbital of aldehyde was important. 2,6-DNBAl was concluded to be less reactive toward water than was 2.4-DNBAl. This is consistent with the experimental result that the mutagenic activity of 2,4-DNBAl depends not only on the reduction of the nitro group by a bacterial enzyme but also on the acetyl conjugation, but that in the case of 2,6-DNBAl the mutagenic activity is manifested through the reduction by a bacterial enzyme. © 1993 John Wiley & Sons, Inc.     

The heat capacity of the doubly reentrant mesogen: 4-cyanobenzoyloxy-4'-octylbenzoyloxy-p-phenylene

Heat capacity of a 20 g sample of the mesogen 4-cyanobenzoyloxy-4'-octylbenzoyloxy-p-phenylene was measured in the temperature range 380 to 510 K by adiabatic calorimetry. The C_p versus T data is interpreted in terms of thermodynamically equivalent S_A1 and S_Ad phases whose Gibbs potential surface intersects the thermodynamically equivalent reentrant nematic and nematic Gibbs potential surface in such a way as to define the first order doubly reentrant phase sequence: S_A1-N-S_Ad-N. The data do not allow any precise estimates of transition enthalpies.     

Anion chromatography using on-line recycled eluents

Non-suppressed anion chromatography, using on-line recycled eluents, was investigated. Cations and anions from samples were excluded from the eluents using a mixture of strongly acidic cation-exchange resins and strongly basic anion exchange resins in the eluent reservoir. This exclusion was performed after determination of the anions in the non-suppressed anion chromatography, and the eluents were then recycled on-line. The performance of consecutive determinations was evaluated from the relative standard deviation (RSD) of peak heights and retention times of chloride, bromide, nitrite, nitrate, and sulfate ions, with a concentration of 3 microg ml(-1) each, compared to that of normal anion chromatography. Over 50 consecutive determinations could be achieved with an eluent volume of only 200 ml for a 100 microl sample volume. Almost all the RSD values for retention time, and peak heights of these anions, were smaller than 3%. Over fifty consecutive determinations of chloride, nitrate, and sulfate ions in a river water sample could be achieved with an eluent volume of only 100 ml. All the RSD values for retention time and peak heights of these anions were smaller than 3%. The eluent volume could be decreased to one tenth of that used in normal anion chromatography. The performance of the anion chromatography, using on-line recycled eluents, was the same as that for normal anion chromatography under the same conditions.     

Alkyl group as entropy reservoir in an MMX chain complex, Pt2(n-PenCS2)4I

Heat capacity of halogen-bridged one-dimensional binuclear metal complex (so-called MMX chain) having four n-pentyl groups, Pt2(n-PenCS2)4I, was measured by adiabatic calorimetry. A first-order phase transition was observed at 207.4 K when measurement was made after cooling from room temperature. The enthalpy and entropy of transition were determined to be 10.19 kJ mol(-1) and 49.1 J K(-1) mol(-1), respectively. A monotropic phase transition was observed at 324 K on heating, and the entropy of transition was essentially null. The sample once heated above 324 K never returned to the initial phase at room temperature and underwent a higher-order phase transition at 173 K and a first-order phase transition at 220.5 K. The enthalpy and entropy of the first-order phase transition were estimated to be 11.6 kJ mol(-1) and 52.4 J K(-1) mol(-1), respectively. The magnitude of the entropy gain at the phase transition from the initial room-temperature phase to the high-temperature phase at 324 K shows that in Pt2(n-PenCS2)4I a large amount of entropy reserved in alkyl chain is transferred to dithiocarboxylato groups upon the phase transition, as in the cases of Pt2(n-PrCS2)4I and Pt2(n-BuCS2)4I.