Liquid-phase microextraction of protein-bound drugs under non-equilibrium conditions

Recently, we introduced an inexpensive and disposable hollow fiber-based device for liquid-phase microextraction (LPME) where ionic analytes typically were extracted and preconcentrated from 1-4 mL aqueous samples (such as plasma and urine) through an organic solvent immobilized in the pores of a polypropylene hollow fiber and into a 10-25 microL volume of acceptor phase present inside the lumen of the hollow fiber. Subsequently, the acceptor phase was directly subjected to the final analysis by a chromatographic or electrophoretic method. In the present work, attention was focused on LPME of the basic drugs amphetamine, pethidine, promethazine, methadone and haloperidol characterized by substantial differences in the degree of protein binding. Drug-protein interactions in plasma resulted in reduced recoveries and substantially increased extraction times compared with extraction of the drugs from a pure water matrix. However, by addition of 5-50% methanol to the plasma samples, recoveries were comparable with LPME from water samples and ranged between 75 and 100%. The addition of methanol was found not to speed up the LPME process and extractions from plasma were performed in 45 min to reach equilibrium. Because approximately 55-70% of the final analyte concentrations were achieved within the initial 10 min of the LPME process, validation was accomplished after 10 and 45 min of LPME. In general, the results with 10 and 45 min were almost comparable, with precision data in the range 1.2-11.1% (RSD) and with linearity in the concentration range 20-1000 ng mL(-1) (r = 0.999). In conclusion, excellent LPME results may be achieved in a short time under non-equilibrium conditions with a minor loss of sensitivity. In cases of drug-protein interactions, methanol may be added to ensure a high extraction recovery.     

从头计算方法比较TiSi_2的C54相和C49相

采用平面波超软赝势描述多电子体系,利用密度泛函理论和广义梯度近似,计算出C54相和C49相TiSi2的晶格常数、体弹性模量、形成能、电子态密度(DOS)和Mulliken电荷布居等性质.通过比较这两种物质的性质,发现尽管两者形成能很相近,但C49相结构对称性差、体弹性模量小、熔点低,Ti原子d轨道的反键强、离子性弱.这些性质上的差异和C49相TiSi2在固相反应中优先形成有关.     

Complete assignments of 1H and 13C NMR data for 10 phenylethanoid glycosides

Ten phenylethanoid glycosides, including two new ones, isolated from the aerial parts of the mangrove plant Acanthus ilicifolius were identified. The first complete assignments of the 1H and 13C NMR chemical shifts for these glycosides were achieved by means of 2D NMR techniques, including 1H-1H COSY, TOCSY, HSQC and HMBC spectra.     

Hydrogenation properties of KSi and NaSi Zintl phases

The recently reported KSi-KSiH(3) system can store 4.3 wt% of hydrogen reversibly with slow kinetics of several hours for complete absorption at 373 K and complete desorption at 473 K. From the kinetics measured at different temperatures, the Arrhenius plots give activation energies (E(a)) of 56.0 ± 5.7 kJ mol(-1) and 121 ± 17 kJ mol(-1) for the absorption and desorption processes, respectively. Ball-milling with 10 wt% of carbon strongly improves the kinetics of the system, i.e. specifically the initial rate of absorption becomes about one order of magnitude faster than that of pristine KSi. However, this fast absorption causes a disproportionation into KH and K(8)Si(46), instead of forming the KSiH(3) hydride from a slow absorption. This disproportionation, due to the formation of stable KH, leads to a total loss of reversibility. In a similar situation, when the pristine Zintl NaSi phase absorbs hydrogen, it likewise disproportionates into NaH and Na(8)Si(46), indicating a very poorly reversible reaction.     

Living Carbocationic Polymerization. XLIX. Two-Stage Living Polymerization of Isobutylene to Di-tert-chlorine Telechelic Polyisobutylene

Abstract

A two-stage process was developed for the living polymerization of isobutylene (IB) employing di-tert-alcohol initiators in conjunction with BCl₃ coinitiator in the first or initiation stage, followed by TiCl₄ coinitiator in the second or propagation stage; the process was shown to yield high molecular weight (up to M ⁿ 20,000), narrow molecular weight distribution (MWD) M ^w/M ⁿ = 1.1–1.2) di-tert-chlorine telechelic polyisobutylenes (^tCl-PIB-Cl^t). The initiation stage involves the homogeneous solution living polymerization of IB induced by the di-tert-alcohol/BCl₃ combination in the presence of an electron donor such as N,N-dimethylacetamide in CH₃Cl solvent at ?80°C and proceeds up to M ⁿ < 5000; this is followed by the propagation stage in which TiCl₄ and the bulk of IB plus a sufficient amount of n-C₆H₁₄ are added to the charge to bring the solvent composition to CH₃Cl/n-C₆H₁₄ 60/40 v/v and the living polymerization is continued until high M ⁿ product is obtained. This two-stage process was developed because 1) it employs very inexpensive chemicals; 2) di-tert-alcohol/BCl₃ combinations initiate living IB polymerization in CH₃Cl but the product after reaching M ⁿ ≤ 5000 precipitates out of the CH₃Cl solution, and di-tert-alcohol/BCl₄ combinations do not initiate IB polymerization; and 3) di-tert-alcohol/BCl₃ systems do not initiate (or only very slowly) the living polymerization of IB in CH₃Cl/n-C₆H₁₄ mixtures, whereas similar TiCl₄-based systems do. The polymerization remains living during both stages although the propagating species and solvent polarity are profoundly altered. The livingness of the system has been analyzed by kinetic experiments and the structure of the ^tCl-PIB-Cl^t product by routine spectroscopic means.     

Electropolymerized m-phenylenediamine as a means to immobilize active protein on thickness-shear-mode quartz crystal

Electropolymerized m-phenylenediamine was used as an active coating for immobilizing urease and lectin on a gold-plated thickness-shear-mode (TSM) crystal. To enhance effectiveness of immobilization. a bilayer polymer film composed of polyaniline and poly-m-phenylenediamine was proposed. Compared with single poly-m-phenylenediamine film, the bilayer polymer film gave better results in terms of immobilizing capacity, stability and reproductivity. On this bilayer-film-coated TSM quartz crystal, the amount of immobilized lectin was estimated about 1.8 mug/cm(2). Detection of purified human erythrocytes is demonstrated as an example of potential application of this lectin-modified TSM biosensor in clinic.     

硫脲化合物的合成及其生物活性

硫脲化合物的合成及其生物活性董燕红，司宗兴（北京农业大学应用化学系北京１０００９４）关键词噻二陛－甲酰基，硫脲，胺类，合成，生物活性酰基硫脲在抗真菌、抗结核、抗病毒、除草以及调节植物生长方面具有广泛应用［１，２］。１，２，３－噻二唑杂环作为有效前体正...     

A new flavanone glucoside from <Emphasis Type="Italic">Abrus precatorius</Emphasis>

A new flavanone glycoside, (2S)5,7,4′-trihydroxyflavanone-8-C-β-D-(6″-O-acetyl)glucopyranoside (1), together with six known flavonoids, isohemiphloin (2), vitexin (3), cirsimaritin (4), hispidulin (5), apigenin (6), and eupatorin (7), was isolated from the leaves and stems of Abrus precatorius. Their structures were elucidated on the basis of physical and spectral analysis. Rotamers exist for compounds 1, 2, and 3. Compounds 1–3, 6, and 7 were isolated from this plant for the first time.     

Chemical composition of essential oils of Litsea cubeba harvested from its distribution areas in China

Litsea cubeba (Lour.) Pers. is a promising industrial crop with fruits rich in essential oils. The chemical composition of essential oils of L. cubeba (EOLC) were determined for fruits harvested from eight regions in China. The overall essential oil content, obtained by hydrodistillation and analyzed by gas chromatography-mass spectrometry (GC-MS), ranged from 3.04% to 4.56%. In total, 59 compounds were identified, the dominant components being monoterpenes (94.4-98.4%), represented mainly by neral and geranial (78.7-87.4%). D-Limonene was unexpectedly a lesser constituent (0.7-5.3%) in fruits, which differed from previous reports (6.0-14.6%). Several components were only detected in certain regions and compounds such as o-cymene and eremophilene have never before been reported in EOLC. These results demonstrate significant regional variation in the chemical composition of EOLC. This investigation provides important information with regard to the bioactivity, breeding work and industrial applications of L. cubeba.     

Synthesis, structural characterization and catalytic activity of a multifunctional enzyme mimetic oxoperoxovanadium(V) complex

The synthesis and structural characterization of a novel oxoperoxovanadium(V) complex [VO(O(2))(PAH)(phen)] containing the ligands 2-phenylacetohydroxamic acid (PAHH) and 1,10-phenanthroline (phen) has been accomplished. The oxoperoxovanadium(V) complex was found to mimic both vanadate-dependent haloperoxidase (VHPO) activity as well as nuclease activity through effective interaction with DNA. The complex is the first example of a structurally characterized stable oxoperoxovanadium(V) complex with a coordinated bi-dentate hydroximate moiety (-CONHO(-)) from 2-phenylacetohydroximate (PAH). The oxoperoxovanadium(V) complex has been used as catalyst for the peroxidative bromination reaction of some unsaturated alcohols (e.g. 4-pentene-1-ol, 1-octene-3-ol and 9-decene-1-ol) in the presence of H(2)O(2) and KBr. The catalytic products have been characterized by GC-MS analysis and spectrophotometric methods. The DNA binding of this complex has been established with CT DNA whereas the DNA cleavage was demonstrated with plasmid DNA. The interactions of the complex with DNA have been monitored by electronic absorption and fluorescence emission spectroscopy. Viscometric measurements suggest that the compound is a DNA intercalator. The nuclease activity of this complex was confirmed by gel electrophoresis studies.