Oxygen in Ge crystals grown by the B2O3 encapsulated Czochralski method

Local vibrations of oxygen in Ge crystals grown by the Czochralski method adopting liquid-B₂O₃ encapsulation and GeO₂ powder doping were investigated by Fourier-transform infrared spectroscopy. Strong absorption peaks at 855 cm⁻¹, originating in local vibration of interstitially dissolved oxygen O_i as Ge–O_i–Ge quasi-molecules, developed depending on the doped amount of GeO₂. Similarly, an absorption peak related to the combined vibration of Ge–O_i–Ge was found at 1264 cm⁻¹ and the conversion factor from the peak intensity to the oxygen concentration was evaluated to be 1.15×10¹⁹ cm⁻². By prolonged annealing at 350 °C an absorption peak developed at 780 cm⁻¹, indicating formation of oxygen-related thermal donors. From the variations of carrier density and oxygen concentration, one donor was found to possess about 15 O_i atoms.     

Sequence-selective DNA detection using multiple laminar streams: a novel microfluidic analysis method

On-site detection methods for DNA have been demanded in the pathophysiology field. Such analysis requires a simple and accurate method, rather than high-throughput. This report describes a novel microfluidic analysis method and its application for simple sequence-selective DNA detection. The method uses a microchannel device with a serpentine structure. Sequence-specific binding of probe DNA can be detected at one side of the microchannel. This method is capable of sequence-specific detection of DNA with high accuracy. Single base mutations can also be analyzed. Combination of laminar stream and laminar secondary flow in the microchannel enable specific detection of probe-bound DNA.     

Turpinionosides A-E: megastigmane glucosides from leaves of Turpinia ternata Nakai

From leaves of Turpenia ternata (Staphylaceae), one megastigmane and seven of its glucosides (1-8) were isolated. Megastigmane and two of the glucosides were found to be known compounds, namely, 3S,5R,6R,9S-tetrahydroxymegastigmane (1), corchoionoside C (2), and icariside B4 (3). The structures of compounds 4-8 (turpinionosides A-E, respectively) were elucidated by means of spectroscopic analyses, and then their absolute structures were determined by the modified Mosher's method to be (3S,5R,6S,9S)-3,6,9-trihydroxymegastigman-7-ene 3-O- and 9-O-beta-D-glucopyranosides (4, 5, respectively), (1S,3S,5R,6S,9R)-3,9,12-trihydroxymegastigmane 3-O-beta-D-glucopyranoside (6), (3S,4R,9R)-3,4,6-trihydroxymegastigman-5-ene 3-O-beta-D-glucopyranoside (7), and (2S,9R)-2,9-dihydroxymegastigman-5-en-4-one 2-O-beta-D-glucopyranoside (8).     

Hybrid QM/MM molecular dynamics simulations for an ionic SN2 reaction in the supercritical water: OH- + CH3Cl --> CH3OH + Cl-

A hybrid real space quantum mechanical/molecular mechanical (RS-QM/MM) method has been applied to an ionic S(N)2 reaction (OH- + CH3Cl --> CH3OH + Cl-) in water solution to investigate dynamic solvation effects of the supercritical water (SCW) on the reaction. It has been demonstrated that the approaching process of OH- to methyl group is prevented by water molecules in the ambient water (AW), while the reaction takes place easily in the gas phase. Almost the same solvation effect on the dynamics of OH- is observed in the SCW, though the bulk density of water is substantially reduced compared with that of the AW. It has been shown that the solvation of the SCW around the OH anion is locally identical to that of the AW due to the strong ion-dipole interactions between OH- and water molecules. At the transition state, the QM/MM simulations have revealed that the excess electron is quite flexible, and the charge volume, as well as the fractional charges on atoms, vary seriously depending on the instantaneous solvent configurations. However, it has been found that the solvation energy in the SCW can be qualitatively related to the HOMO volume of the system by Born's equation.     

Fe(3+) coordinated to amino-functionalized MCM-41: an adsorbent for the toxic oxyanions with high capacity, resistibility to inhibiting anions, and reusability after a simple treatment

Fe(3+) coordinated to amino ligands fixed on MCM-41 mesoporous silica works as a strong adsorbent for toxic oxyanions. The maximum adsorption amounts were 1.56, 0.99, 0.81, and 1.29 mmol g(-1) for arsenate, chromate, selenate, and molybdate, respectively. When the initial concentrations of oxyanions were less than 1 mmol l(-1), they were removed completely by adsorption and the distribution coefficients K(d) were found to be more than 200000. Inhibition of oxyanion adsorption by abundant competing anions found in nature, NO(3)(-), SO(4)(-), PO(4)(3)(-) and Cl(-), was evaluated at adsorption saturation. Among these anions, the adsorption of the oxyanions was inhibited most in the presence of PO(4)(3)(-) , with which the selectivities for the target oxyanions were still more than 80%. The other coexisting anions, NO(3)(-), SO(4)(-), PO(4)(3)(-) and Cl(-), had little influence on adsorption of the oxyanions except in the case of selenate removal from sulfate solution. The high ability and selectivity to the target oxyanions are attributed to specific interactions between Fe(3+) and the oxyanions. The acid treatment and re-coordination of Fe(3+) lead to a reactivation of the used adsorbent, in which 87-90% of the original adsorption capacity was obtained and the oxyanion/Fe stoichiometries were not changed.     

Phenylethanoid and iridoid glycosides from the Thai medicinal plant, Barleria strigosa

A phenylethanoid (4-hydroxyphenylethyl 4-O-beta-D-glucopyranosyl-(1-->3)-O-alpha-L-rhamnopyranoside) and an iridoid (10-O-trans-coumaroyl-eranthemoside) were isolated from an entire Barleria strigosa plant together with verbascoside, isoverbascoside, decaffeoylverbascoside, (+)-lyoniresinol 3alpha-O-beta-D-glucoside, apigenin 7-O-alpha-L-rhamnosyl-(1-->6)-O-beta-D-glucoside, 7-O-acetyl-8-epi-loganic acid and (3R)-1-octen-3-ol-3-O-beta-D-xylosyl-(1-->6)-beta-D-glucoside. The structural elucidations were based on analyses of physical and spectroscopic data.     

Biosynthesis of indole diterpenes, emindole, and paxilline: involvement of a common intermediate

The key step for construction of the carbon skeleton in the indole diterpenes, paxilline, and emindole DA was examined. Intact incorporation of multiply (2)H-labeled 3-geranylgeranylindole into two different fungal metabolites proves 3-geranylgeranylindole to be a biosynthetic intermediate. These results give evidence that indole diterpenes are biosynthesized via epoxidation of a common intermediate, and the subsequent cationic cyclization, analogous to those in the steroid biosynthesis. [structure: see text]     

Molecular design, characterization, and application of multiinformation dyes for optical chemical sensing: IV. Multiinformation dyes with extended spectral sensitivity in the near-infrared spectral range

In this paper, new “multiinformation dyes” (MIDs) with extended spectral sensitivity reporting on both changes in solvent polarity (solvatochromism) and in pH (halochromism) by changes in their visible absorption spectra, are presented. The merocyanine dyes 2,6-dibromo-4-[4-(1-dodecyl-4(1H)-pyridinylidene)-2-butenylidene]-2,5-cyclohexadien-1-one (KD-M301) and 2,6-dibromo-4-[4-(1-dodecyl-4(1H)-quinolinylidene)-2-butenylidene]-2,5-cyclohexadien-1-one (KD-M402) were designed, synthesized, and characterized regarding analytical applications. The spectral sensitivity for the MIDs was extended into the near-infrared (NIR) wavelength range (λ_max=800 nm in CHCl₃ for KD-M402) and at the same time, the degree of solvent polarity-induced spectral shifts was strongly enhanced (Δλ_max=202 nm for KD-M402 between tetrahydrofuran (THF) and methanol), reaching similar values to the standard solvatochromic dye Dimroth-Reichardt’s betaine on which the empirical E_T(30) classification of solvent polarity is based. Compared to Dimroth-Reichardt’s betaine dye, the molar absorption coefficient ε, is increased more than 10-fold (ε of KD-M402 in THF: 7.7×10⁴ M⁻¹ cm⁻¹), allowing sensitive measurements at low concentrations of the dye. The dodecyl-substituted KD-M402 is suitable as a lipophilic pH indicator in ion-exchange type optical sensors (optodes) with optical detection in the near-infrared wavelength range.