Rapid determination of panaxynol in a traditional Chinese medicine of Saposhnikovia divaricata by pressurized hot water extraction followed by liquid-phase microextraction and gas chromatography-mass spectrometry

Panaxynol is a bioactive component in traditional Chinese medicines (TCMs), such as Saposhnikovia divaricata and Panax ginseng. In the work, two solvent-free sample techniques of pressurized hot water extraction (PHWE) and headspace liquid-phase microextraction (HS-LPME) were combined and developed for the determination of panaxynol in a TCM of S. divaricata. Panaxynol in the TCM samples from different growing areas was extracted by PHWE in dynamic mode, followed by extraction and concentration with HS-LPME and analysis with gas chromatography-mass spectrometry (GC-MS). The PHWE and HS-LPME parameters were optimized and the method validations were studied. Panaxynol in S. divaricata from four different growing areas was quantitatively analyzed by internal standard method. These results have shown that PHWE-LPME-GC-MS is a simple, rapid, efficient and low-cost method for the determination of panaxynol in TCMs and is a potential tool for TCM quality assessment.     

Application of Hot Press Sintering to Na2O-B2O3-SiO2 Gels Containing Quantum Dots for Lowering of Densification Temperature

Na₂O-B₂O₃-SiO₂ (NBS) gels containing a large amount of CdS quantum-dots (10 wt%) were densified using the hot press (HP) sintering method. By HP treatment, full-densification temperature could be lowered by about 40°C than that of the normal non-pressing (NP) heat treatment. Exciton absorption of CdS quantum-dots in HP-sample showed a large blue shift compared with that in the NP sample, and the size-distribution of CdS dots remained very sharp, with a mean particle diameter d = 3.66 nm and a standard deviation of = 0.72. HP pressure had a large effect on the reduction of sintering temperature and time, resulting in the suppression of the aggregation and growth of CdS quantum-dots in NBS glasses.     

Cathodic electrochemiluminescence at double barrier Al/Al2O3/Al/Al2O3 tunnel emission electrodes

Double insulating barrier tunnel emission electrodes were fabricated by adding a new pure aluminum layer upon oxidized aluminum electrodes by vacuum evaporation and thermally oxidizing the new aluminum layer in air at room temperature. Resulting Al/Al₂O₃/Al/Al₂O₃ electrodes allow the use of various aluminum alloys in the electrode body necessary for hardness or shaping ability of the electrode while obtaining the luminescence properties of pure aluminum oxide. During electrical excitation of luminescent labels by cathodic hot electron injection into aqueous electrolyte solution, the background noise is mainly based on high-field-induced solid-state electroluminescence and F-center luminescence of the outer aluminum oxide film. The more defect states and/or impurity centers the outer oxide film contains, the higher is the background emission intensity. The present electrode fabrication method provides a considerable improvement in signal-to-noise ratio for time-resolved electrochemiluminescence (TR-ECL) measurements when the original native oxide film of the electrode body contains luminescence centers displaying long-lived luminescence. The excellent performance of the present electrodes is demonstrated by extremely low-level detection of Tb(III) chelates, luminol, Pt(II) coproporphyrin and Tb(III) labels in an immunometric immunoassay by time-resolved electrochemiluminescence.     

对辣椒色素某些性能的测试

对辣椒色素某些性能的测试陈连文（河北经贸大学轻工系石家庄０５００６１）刘敬兰（河北师范大学实验中心石家庄０５００１６）关键词分离辣椒色素测定红辣椒属茄科，辣椒属（ＣａｐｓｉｃｕｍｆｒｕｔｅｓｃｅｎｓＬ．），我国各地均有栽培，品种多，资源丰富。内服有开...     

meso-substituted aromatic 34pi core-modified octaphyrins: syntheses,characterization and anion binding properties

Modified octaphyrins with 34pi electrons have been synthesized and characterized following a simple synthetic methodology. An acid-catalyzed alpha,alpha coupling of tetrapyrranes containing furan, thiophene and selenophene rings resulted in the formation of the respective octaphyrins in relatively good yield. Solution studies by (1)H NMR and 2D NMR methods and single crystal Xray structural characterization reveal an almost flat structure with two heterocyclic rings inverted. Specifically, in 14 two selenophene rings (one on each biselenophene unit) are inverted while in 15 two furan rings (one on each bifuran unit) are inverted when the meso substituent are mesityl groups. On changing the mesityl substituent to m-xylyl group as in 19, the location of ring inversion shifts to pyrrole rings (one on each bipyrrole unit) indicating the dependence of structure on the meso substituents. UV/Vis studies, both in freebase and protonated forms reveal typical porphyrinic character and the aromatic nature of the octaphyrins. The Deltadelta values evaluated by (1)H NMR spectroscopy also support their aromatic nature. The protonated forms of octaphyrins bind TFA anion in a 1:2 ratio. The TFA anions are located one above and below the plane of the octaphyrin macrocycle and they are held by weak electrostatic NH-O interactions similar to that observed for protonated rubyrins. However, in the present case, there is an additional non-electrostatic CH-O interaction involving beta-CH of the inverted heterocyclic ring and the carbonyl oxygen of the TFA. Furthermore, inter molecular interactions between the Cbond;H of the meso-mesityl group and the fluorine of CF(3) group of bound TFA leads to the formation of one-dimensional supramolecular arrays with interplanar distance of 13 A between two octaphyrins.     

One site fits both: A model for the ternary complex of folate + NADPH in R67 dihydrofolate reductase, a D2 symmetric enzyme

R67 dihydrofolate reductase (DHFR) is a novel enzyme that confers resistance to the antibiotic trimethoprim. The crystal structure of R67 DHFR displays a toroidal structure with a central active-site pore. This homotetrameric protein exhibits 222 symmetry, with only a few residues from each chain contributing to the active site, so related sites must be used to bind both substrate (dihydrofolate) and cofactor (NADPH) in the productive R67 DHFR?NADPH?dihydrofolate complex. Whereas the site of folate binding has been partially resolved crystallographically, an interesting question remains: how can the highly symmetrical active site also bind and orient NADPH for catalysis? To model this ternary complex, we employed DOCK and SLIDE, two methods for docking flexible ligands into proteins using quite different algorithms. The bound pteridine ring of folate (Fol I) from the crystal structure of R67 DHFR was used as the basis for docking the nicotinamide-ribose-P_i (NMN) moiety of NADPH. NMN was positioned by both DOCK and SLIDE on the opposite side of the pore from Fol I, where it interacts with Fol I at the pore's center. Numerous residues serve dual roles in binding. For example, Gln 67 from both the B and D subunits has several contacts with the pteridine ring, while the same residue from the A and C subunits has several contacts with the nicotinamide ring. The residues involved in dual roles are generally amphipathic, allowing them to make both hydrophobic and hydrophilic contacts with the ligands. The result is a `hot spot' binding surface allowing the same residues to co-optimize the binding of two ligands, and orient them for catalysis.     

The synthetic microporous tellurites Na2[Me 2(TeO3)3]·3H2O (Me=Zn,Co): Crystal structure,De- and rehydration,and ion exchange properties

Summary The crystal structure investigations of hydrothermally synthesized Na₂[Zn₂(TeO₃)₃]·3H₂O (NZT) and Na₂[Co₂(TeO₃)₃]·3H₂O (NCT) using single-crystal X-ray diffraction methods revealed a microporous framework structure of hexagonal symmetry with tubular channels running parallel to the c-axis (zemannite type). The statistically occupied sites of the Na⁺ ions and H₂O molecules within the channels as well as the channel dimensions indicate a possible zeolitic behaviour of the compounds. Thermoanalytical investigations ofNZT show an irreversible breakdown of the framework already atT=533 K caused by complete dehydration. A reversible rehydration was solely observed for partially dehydratedNZT (T493 K); a remarkable ion exchange rate from alkali-chloride solutions was observed only for Li⁺. Both the rehydration and the ion exchange properties are characterized by relatively long reaction times. The relatively poor zeolitic properties compared to typical zeolitic compounds could be related to the stereochemical activity of the lone-pair electrons of the Te⁴⁺ atoms which claim a certain volume within the channels and constrict the effective channel dimension to a free diameter of approximately 2.5 Å.

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Die synthetischen zeolithartigen Tellurite Na₂[Me ₂(TeO₃)₃]·3H₂O (Me=Zn, Co): Kristallstruktur, De- und Rehydratisierung und Ionenaustauschvermögen

Zusammenfassung Die Kristallstrukturuntersuchungen mittels Röntgen-Einkristalldiffraktionsmethoden von hydrothermal dargestelltem Na₂[Zn₂(TeO₃)₃]·3H₂O (NZT) und Na₂[Co₂(TeO₃)₃]·3H₂O (NCT) ergaben eine zeolithartige Gerüststruktur hexagonaler Symmetrie mit parallel zur c-Achse angeordneten röhrenartigen Kanälen (Zemannittyp). Die statistisch besetzten Punktlagen der Na⁺-Atome und H₂O Moleküle innerhalb der Kanäle wie auch die Kanaldimensionen selbst weisen auf mögliche zeolithische Eigenschaften der Verbindungen hin. Thermoanalytische Untersuchungen anNZT ergaben einen irreversiblen Zusammenbruch der Gerüststruktur bereits beiT=533 K durch vollständige Entwässerung. Eine reversible Rehydratisierung wurde nur für partiell entwässertesNZT (T493 K) beobachtet; ein nennenswerter Ionenaustausch aus Alkalichlorid-Lösungen konnte nur für Li⁺ bestimmt werden. Sowohl die Rehydratisierung als auch das Ionenaustauschvermögen sind durch relativ lange Reaktionszeiten charakterisiert. Die im Vergleich zu typisch zeolithischen Verbindungen relativ schlechten zeolithischen Eigenschaften konnten auf die stereochemische Aktivität der einsamen Elektronenpaare der Te⁴⁺ Atome zurüchgefürt werden, die einen gewissen Platz innerhalb der Kanäle beanspruchen und den effektiven freien Durchmesser der Kanäle auf etwa 2.5 Å einengen.

     

Heterogeneous and homogeneous electrochemiluminoimmunoassays of hTSH at disposable oxide-covered aluminum electrodes

Heterogeneous and homogeneous immunoassays of human thyroid stimulating hormone (hTSH) were developed on immunometric basis using aromatic Tb(III) chelates as electrochemiluminescent labels and varied types of disposable oxide-covered aluminum electrodes as the solid phase of the immunoassays. The long luminescence lifetime of the present labels allows the use of time-resolved electrochemiluminescence detection and provide the low detection limits of these labels and, thus, sensitive immunoassays. The primary antibody of immunometric immunoassays was coated upon aluminum oxide surface by physical absorption. In homogeneous immunoassays using 66 μl cell and 15 min incubation time, a linear calibration range of 0.25-324 μU/ml was obtained by applying only a single cathodic excitation pulse in the detection step of the assay.     

Molten salt flux synthesis and structure of the new layered uranyl tellurite, K4[(UO2)5(TeO3)2O5]

The reaction of UO₃ and TeO₃ with a KCl flux at 800 °C for 3 days yields single crystals of K₄[(UO₂)₅(TeO₃)₂O₅]. The structure of the title compound consists of layered, two-dimensional sheets arranged in a stair-like topology separated by potassium cations. Contained within these sheets are one-dimensional uranium oxide ribbons consisting of UO₇ pentagonal bipyramids and UO₆ tetragonal bipyramids. The ribbons are in turn linked by corner-sharing with trigonal pyramidal TeO₃ units to form sheets. The lone-pair of electrons from the TeO₃ groups are oriented in opposite directions with respect to one another on each side of the sheets rendering each individual sheet nonpolar. The potassium cations form contacts with nearby tellurite units and axial uranyl oxygen atoms. Crystallographic data (193 K, MoKα, ): triclinic, space group , , , , α=99.642(1)°, β=93.591(1)°, γ=100.506(1)°, , Z=1,R(F)=4.19% for 149 parameters and 2583 reflections with I>2σ(I).