Stereochemical control of Zn(II)/Cu(II) selectivity in piperidine tripod ligands

Stereochemistry plays a major role in the selectivity toward zinc ion over copper(II) of some tripodal ligands with a central piperidine scaffold, one of which acts as a fluorescent zinc sensor with nanomolar sensitivity.     

A dual-electrode approach for highly selective detection of glucose based on diffusion layer theory: experiments and simulation

A dual-electrode configuration for the highly selective detection of glucose in the diffusion layer of the substrate electrode is presented. In this approach, a glassy carbon electrode (GCE, substrate) modified with a conductive layer of glucose oxidase/Nafion/graphite (GNG) was used to create an interference-free region in its diffusion layer by electrochemical depletion of interfering electroactive species. A Pt microelectrode (tip, 5 microm in radius) was located in the diffusion layer of the GNG-modified GCE (GNG-G) with the help of scanning electrochemical microscopy. Consequently, the tip of the electrode could sense glucose selectively by detecting the amount of hydrogen peroxide (H2O2) formed from the oxidization of glucose on the glucose oxidase layer. The influences of parameters, including tip-substrate distance, substrate potential, and electrolyzing time, on the interference-removing efficiency of this dual-electrode approach have been investigated systematically. When the electrolyzing time was 30 s, the tip-substrate distance was 1.8 a (9.0 microm) (where a is the radius of the tip electrode), the potentials of the tip and substrate electrodes were 0.7 V and 0.4 V, respectively, and a mixture of ascorbic acid (0.3 mM), uric acid (0.3 mM), and 4-acetaminophen (0.3 mM) had no influence on the glucose detection. In addition, the current-time responses of the tip electrode at different tip-substrate distances in a solution containing interfering species were numerically simulated. The results from the simulation are in good agreement with the experimental data. This research provides a concept of detection in the diffusion layer of a substrate electrode, as an interference-free region, for developing novel microelectrochemical devices.     

Importance of supersuperexchange interactions in determining the dimensionality of magnetic properties. Determination of strongly interacting spin exchange paths in A(2)Cu(PO(4))(2) (A = Ba, Sr), ACuP(2)O(7) (Ba, Ca, Sr, Pb), CaCuGe(2)O(6), and Cu(2)UO(2)(PO(4))(2) on the basis of qualitative spin dimer analysis

The patterns of the Cu(2+) ion arrangements in the magnetic oxides A(2)Cu(PO(4))(2) (A = Ba, Sr), ACuP(2)O(7) (Ba, Ca, Sr, Pb), CaCuGe(2)O(6), and Cu(2)UO(2)(PO(4))(2) are quite different from the patterns of the strongly interacting spin exchange paths deduced from their magnetic properties. This apparently puzzling observation was explained by evaluating the strengths of the Cu-O-Cu superexchange and Cu-O...O-Cu supersuperexchange interactions of these oxides on the basis of qualitative spin dimer analysis. Supersuperexchange interactions are found to be crucial in determining the dimensionality of magnetic properties of these magnetic oxides.     

Synthesis of titanium dioxide nanoparticles with mesoporous anatase wall and high photocatalytic activity

Mesoporous titanium dioxide nanosized powder with high specific surface area and anatase wall was synthesized via hydrothermal process by using cetyltrimethylammonium bromide (CTAB) as surfactant-directing agent and pore-forming agent. The resulting materials were characterized by XRD, nitrogen adsorption, FESEM, TEM, and FT-IR spectroscopy. The as-synthesized mesoporous TiO2 nanoparticles have mean diameter of 17.6 nm with mean pore size of 2.1 nm. The specific surface area of the as-synthesized mesoporous nanosized TiO2 exceeded 430 m2/g and that of the samples after calcination at 600 degrees C still have 221.9 m2/g. The mesoporous TiO2 nanoparticles show significant activities on the oxidation of Rhodamine B (RB). The large surface area, small crystalline size, and well-crystallized anatase mesostructure can explain the high photocatalytic activity of mesoporous TiO2 nanoparticles calcined at 400 degrees C.     

A new tetrathiafulvalene–diamide cation salt with [Cu2Br4]2− anions

The title salt, bis[2,3‐bis(aminocarbonyl)‐8,9‐bis(methylsulfanyl)tetrathiafulvalenium] di‐μ‐bromido‐bis[bromidocopper(II)], (C₁₀H₁₀N₂O₂S₆)₂[Cu₂Br₄], contains 2,3‐bis(aminocarbonyl)‐8,9‐bis(methylsulfanyl)tetrathiafulvalenium radical cations, [DMT‐TTF(CONH₂)₂]^·+, and [Cu₂Br₄]²⁻ anions. The cations are associated across centres of inversion in a head‐to‐tail fashion via short face‐to‐face S...S stacking (TTF moiety). These dimers are further assembled into a one‐dimensional chain structure via interdimer double S...S contacts involving the methylsulfanyl groups. The one‐dimensional chains give rise to a two‐dimensional structure through intermolecular double N—H...O hydrogen bonds involving the amide group. The [Cu₂Br₄]²⁻ anions, which straddle centres of inversion, are located between the cation layers. Electron paramagnetic resonance measurements show a radical signal, indicating that the two TTF^·+ radicals are not completely coupled in the dimer.     

Dysfunction of Shh signaling activates autophagy to inhibit trophoblast motility in recurrent miscarriage

In early pregnancy, the placenta anchors the conceptus and supports embryonic development and survival. This study aimed to investigate the underlying functions of Shh signaling in recurrent miscarriage (RM), a serious disorder of pregnancy. In the present study, Shh and Gli2 were mainly observed in cytotrophoblasts (CTBs), Ptch was mainly observed in syncytiotrophoblasts (STBs), and Smo and Gli3 were expressed in both CTBs and STBs. Shh signaling was significantly impaired in human placenta tissue from recurrent miscarriage patients compared to that of gestational age-matched normal controls. VEGF-A and CD31 protein levels were also significantly decreased in recurrent miscarriage patients. Furthermore, inhibition of Shh signaling impaired the motility of JAR cells by regulating the expression of Gli2 and Gli3. Intriguingly, inhibition of Shh signaling also triggered autophagy and autolysosome accumulation. Additionally, knockdown of BECN1 reversed Gant61-induced motility inhibition. In conclusion, our results showed that dysfunction of Shh signaling activated autophagy to inhibit trophoblast motility, which suggests the Shh pathway and autophagy as potential targets for RM therapy.Subject terms: Embryology, Endocrine reproductive disorders, Autophagosomes     

The effect of the trifluoropropyl group in polysiloxane stationary phases used for capillary gas chromatography

Four poly(methyl 3,3,3-trifluoropropyl siloxanes) with trifluoro-propyl group content (group substitution) between 8 and 35 percent have been synthesized and characterized as stationary phases for gas chromatography in borosilicate glass capillary columns. Results are compared with those from two commercial stationary phases–a polydimethylsiloxane and a poly(methyl 3,3,3-trifluoropropyl siloxane) with a fifty percent trifluoropropyl group content (group substitution). Retention index values, McReynolds constants, polarity (as defined by McReynolds) and retention polarity (as defined by Takács) increase regularly with the trifluoropropyl group content of the stationary phase. The temperature coefficient of the retention indices of the McReynolds probes, and that of the polarities, have been determined at temperatures between 60 and 180 °C. Specific retention volumes do not follow the linear dependence on trifluoropropyl group content observed for retention indices or polarities. Substances with electron-donor groups show maximum retention for a trifluoropropyl group content of ca 30%, whereas the retention of hydrocarbons, halogenated compounds, and alcohols decreases as the degree of trifluoropropyl group substitution increases from 0 to 50%. It is felt that a polysiloxane with a trifluoropropyl group content of ca 30 to 35% would be the best choice for the separation of ketones, nitro compounds or amines.     

Oxidation resistant germanium nanowires: bulk synthesis, long chain alkanethiol functionalization, and Langmuir-Blodgett assembly

A simple method is developed to synthesize gram quantities of uniform Ge nanowires (GeNWs) by chemical vapor deposition on preformed, monodispersed seed particles loaded onto a high surface area silica support. Various chemical functionalization schemes are investigated to passivate the GeNW surfaces using alkanethiols and alkyl Grignard reactions. The stability of functionalization against oxidation of germanium for various alkyl chain lengths is elucidated by X-ray photoelectron spectroscopy. Among all schemes tested, long chain alkanethiols (> or = C12) are found to impart the most stable GeNW passivation against oxidation upon extended exposure to ambient air. Further, the chemically functionalized oxidation-resistant nanowires are soluble in organic solvents and can be readily assembled into close-packed Langmuir-Blodgett films potentially useful for future high performance electronic devices.     

ATMP(氨基三甲叉膦酸)及其顺磁性Co(Ⅱ)配合物的核磁共振研究

本文用¹H、³¹P和¹³C核磁共振谱研究了ATMP(氨基三甲叉膦酸,以简式H₆L表示)及其顺磁性Co(Ⅱ)配合物。测定了不同C_co/C_ATMP摩尔比在不同pH值下的各向同性位移。定性地讨论顺磁性Co(Ⅱ)配合物在不同pH条件下的组成、电荷和空间构型变化对化学位移的影响。运用快速交换反应中化学位移与配合物浓度的关系,确定不同pH下的条件稳定常数。