Direct Detection of Al–O–Al Structure in Aluminosilicate Specimens: A Use of Homo-Nuclear DQMAS NMR

A general strategy of Al–O–Al structure in various aluminosilicate was evaluated by combining triple-quantum magic angle spinning (3QMAS) and double-quantum homo-nuclear correlation under magic angle spinning (DQMAS) solid-state nuclear magnetic resonance (NMR) measurements with the aid of high magnetic field NMR (800 MHz for ¹H Larmor frequency). The results show that in many cases the direct detection of Al–O–Al sites in aluminosilicate crystals and glasses is possible; hence the extent of aluminum avoidance can be directly elucidated. Specifically, experimental evidence of Al–O–Al linkages in several aluminosilicate materials with Si/Al >1 was straightforwardly confirmed; and the existence of Al–O–Al is considered to have little correlation with the Si/Al ratio, but it may be strongly related to the cation and local structural arrangement. In addition, the presence of tri-clusters of (Si, Al)O₄-tetrahedra in aluminosilicate framework was proposed, which was thought to act as nuclei for formation and incorporation of cations to achieve charge neutrality.     

Stereocontrolled synthesis of an indole moiety of sespendole and stereochemical assignment of the side chain

Two possible diastereomers of the indole moiety of sespendole were synthesized from 3-hydroxy-4-nitrobenzaldehyde in a highly stereoselective manner. Comparison of (1)H and (13)C NMR spectra of the two synthetic materials with those sespendole leads us to propose that the relative stereochemistry of the epoxyalcohol is syn.     

Simultaneous enantiomeric determination of MDMA and its phase I and phase II metabolites in urine by liquid chromatography–tandem mass spectrometry with chiral derivatization

A liquid chromatography–electrospray ionization tandem mass spectrometry (LC-ESI-MS/MS) procedure was developed for the simultaneous determination of enantiomers of the prevalent designer drug 3,4-methylenedioxymethamphetamine (MDMA) and its phase I and phase II metabolites in urine with chiral derivatization. The analytes in urine were directly derivatized with chiral Marfey’s reagent, N ^α- (5-fluoro-2,4-dinitrophenyl)-d-leucinamide, without extraction. The diastereomers of the N ^α-(2,4-dinitrophenyl)-d-leucinamide derivatives generated were determined by LC-MS/MS. Satisfactory chromatographic separation was achieved for the enantiomers of MDMA and its metabolites 3,4-methylenedioxyamphetamine, 4-hydroxy-3-methoxymethamphetamine (HMMA), HMMA glucuronide, and HMMA sulfate on a semimicro octadecylsilane column using linear gradient elution. With use of multiple reaction monitoring mode, the limits of detection of these analytes ranged from 0.01 to 0.03?μg/mL. Linear calibration curves were obtained for all enantiomers from 0.1 to 20?μg/mL in urine. The method showed sufficient reproducibility and quantitative ability. This is the first report of a simple LC-MS/MS-based analytical procedure with direct chiral derivatization in aqueous media that allows simultaneous enantiomeric determination of drugs and their metabolites, including glucuronide and sulfate derivatives.     

Spontaneous emission control of CdSe/ZnS nanoparticle monolayer in polymer nanosheet waveguide assembled on a one-dimensional silver grating surface

We present spontaneous emission control of a core-shell CdSe/ZnS nanoparticle array assembled with polymer ultrathin films consisting of polymer nanosheets on a silver grating substrate, which served as a unique and simple photonic cavity. The grating-coupled waveguide modes enabled 10(3) order luminescence enhancement and one-fourth spectral narrowing. The light emission from a CdSe/ZnS nanoparticle array can be controlled by tuning the film thickness of hybrid polymer nanoassemblies, which provides multiple emission performance with good tuning ability from red to green at low-power continuous wave laser excitation (～μW).     

Rapid transformation from spherical nanoparticles, nanorods, cubes, or bipyramids to triangular prisms of silver with PVP, citrate, and H2O2

Rapid sphere-to-prism (STP) transformation of silver was studied in aqueous AgNO(3)/NaBH(4)/polyvinylpyrrolidone (PVP)/trisodium citrate (Na(3)CA)/H(2)O(2) solutions by monitoring time-dependent surface plasmon resonance (SPR) bands in the UV-vis region, by examining transmission electron microscopic (TEM) images, and by analyzing emitted gases during fast reaction. Roles of PVP, Na(3)CA, and H(2)O(2) were studied without addition of a reagent, with different timing of each reagent's addition, and with addition of H(2)O(2) to mixtures of spheres and prisms. Results show that prisms can be prepared without addition of PVP, although it is useful to synthesize smaller monodispersed prisms. A new important role of citrate found in this study, besides a known role as a protecting agent of {111} facets of plates, is an assistive agent for shape-selective oxidative etching of Ag nanoparticles by H(2)O(2). The covering of Ag nanoparticles with carboxylate groups is necessary to initiate rapid STP transformation by premixing citrate before H(2)O(2) addition. Based on our data, rapid prism formation starts from the consumption of spherical Ag particles because of shape-selective oxidative etching by H(2)O(2). Oxidative etching of spherical particles by H(2)O(2) is faster than that of prisms. Therefore, spherical particles are selectively etched and dissolved, leaving only seeds of prisms to grow into triangular prisms. When pentagonal Ag nanorods and a mixture of cubes and bipyramids were used as sources of prisms, rod-to-prism (RTP), cube-to-prism (CTP), and bipyramid-to-prism (BTP) transformations were observed in Ag nanocrystals/NaBH(4)/PVP/Na(3)CA/H(2)O(2) solutions. Shape-selective oxidative etching of rods was confirmed using flag-type Ag nanostructures consisting of a triangular plate and a side rod. These data provide useful information for the size-controlled synthesis of triangular Ag prisms, from various Ag nanostructures and using a chemical reduction method, having surface plasmon resonance (SPR) bands at a desired wavelength.     

Optical path-length matrix method for estimating skin spectrum

In this article, we propose a new method??the optical path-length matrix method (OPLM)??as a faster alternative to the Monte Carlo for multi-layered media (MCML), which is often used to simulate the skin spectrum. Theoretically, peripheral oxygen saturation can be estimated by iterating MCML, but it is not a realistic strategy because it requires huge computation time. The optical path-length matrix is obtained as the probabilistic density histograms of the optical path length in skin using MCML, and once the matrix is obtained, skin spectral reflectance can be calculated by accumulating all combinations of elements in the matrix and by setting an absorption coefficient based on the Beer-Lambert law. The computational time of OPLM was approximately 26,000 times faster than that of MCML.     

Xanthene dyes induce membrane permeabilization of bacteria and erythrocytes by photoinactivation

We analyzed the photoinactivation of the membrane functions of bacteria and erythrocytes induced by xanthene dyes. The dyes tested were rose bengal, phloxine B, erythrosine B and eosin B. These dyes induced the leakage of K(+) from Staphylococcus aureus cells within minutes of photoirradiation, in the order of rose bengal > phloxine B > erythrosine B > eosin B. The ability of dyes to inhibit respiration was weak, except for rose bengal, and the dyes dissipated the membrane potential in similar time traces with changes in K(+) permeability. The xanthene dyes also induced the leakage of K(+) from bovine erythrocytes upon photoirradiation in the same order as that observed with bacteria. Furthermore, we found that the ability to cause the leakage of K(+) from erythrocytes was associated with dye-induced morphological changes, forming a crenated form from the normal discoid. These results are discussed in connection with the ability of xanthene dyes to generate singlet oxygen and bind to bacterial cells, and further compared with the actions of cationic porphyrins, which induced photoinactivation of bacteria through respiratory inhibition.     

The First in Vivo Observation of C–N Coupling in Mammalian Brain

[5-¹³C,¹⁵N]Glutamine, with ¹J(¹³C–¹⁵N) of 16 Hz, was observed in vivo in the brain of spontaneously breathing rats by ¹³C MRS at 4.7 T. The brain [5-¹³C]glutamine peak consisted of the doublet from [5-¹³C,¹⁵N]glutamine and the center [5-¹³C,¹⁴N]glutamine peak, resulting in an apparent triplet with a separation of 8 Hz. The time course of formation of brain [5-¹³C,¹⁵N]glutamine was monitored in vivo with a time resolution of 20–35 min. This [5-¹³C,¹⁵N]glutamine was formed by glial uptake of released neurotransmitter [5-¹³C]glutamate and its reaction with ¹⁵NH₃ catalyzed by the glia-specific glutamine synthetase. The neurotransmitter glutamate C5 was selectively¹³C-enriched by intravenous [2,5-¹³C]glucose infusion to ¹³C-label whole-brain glutamate C5, followed by [¹²C]glucose infusion to chase ¹³C from the small and rapidly turning-over glial glutamate pool, leaving ¹³C mainly in the neurotransmitter [5-¹³C]glutamate pool, which is sequestered in vesicles until release. Hence, the observed [5-¹³C,¹⁵N]glutamine arises from a coupling between ¹³C of neuronal origin and ¹⁵N of glial origin. Measurement of the rate of brain [5-¹³C,¹⁵N]glutamine formation provides a novel noninvasive method of studying the kinetics of neurotransmitter uptake into glia in vivo, a process that is crucial for protecting the brain from glutamate excitotoxicity.     

Reaction of 2-Alkoxypropenals with 2-Mercaptoethanol

The reaction between 2-alkoxypropenals and 2-mercaptoethanol was studied at 20 and 60°C by means of ^1HNMR and GC-MS methods. Under kinetically controlled conditions (20°C, 7-30 days) with no catalyst the addition of 2-mercaptoethanol to 2-alkoxypropenals occurs along Markownikoff rule. The arising 2'-hydroxyethylthio-2-alkoxypropanal undergoes isomerization into the 2-hydroxy-3-alkoxy-3-methyl-1,4-oxathiane that at heating in the presence of catalytic amounts of acids is converted into 2-methyl-2-formyl-1,3-oxathiolane. The reaction of 2-alkoxypropenals with 2-mercaptoethanol at heating (60°C, 3 h) in the presence of acids affords 2-methyl-2,2'-bi(1,3-oxathiolane) even at 2-mercaptoethanol deficit. At the double excess of the latter the 2-methyl-2,2'-bi(1,3-oxathiolane) was obtained in quantitative yield. The presumable schemes of conversion of 2-hydroxy-3-alkoxy-3-methyl-1,4-oxathiane into 2-methyl-2-formyl-1,3-oxathiolane and 2-acetyl-1,3-oxathiolane are discussed.