Strong Attraction of Caffeine to the Mercurous Dumbbell in the Salt [Hg2(Caf)2](ClO4)2(H2O)2

Colourless single crystals of the caffeine adduct of mercurous perchlorate dihydrate, [Hg₂(Caf)₂](ClO₄)₂(H₂O)₂, were grown from aqueous solutions of mercurous perchlorate and caffeine by isothermal evaporation at ambient temperature. The crystal structure (monoclinic, P2₁/n, Z = 4, a = 1628.0(2), b = 780.4(1), c = 2229.6(3) pm, β = 99.84(1)°, R₁(all data) = 0.0894) contains [trans‐Caf‐Hg‐Hg‐Caf]²⁺ cations with a Hg‐Hg distance of 250.88(6) pm, Hg‐N (bond) distances of 214.4(6) and 215.1(6) pm and Hg‐Hg‐N angles of 176.9(2) and 165.1(2)°, respectively. These cations are attached via weak Hg‐O contacts to dimers which are further arranged to leave large channels into which one crystal water molecule is included. The second water molecule and the two perchlorate anions are weakly attracted to one Hg atom.     

Morphology and thermal properties of a PC/PE blend with reactive compatibilization

Reactive compatibilization of immiscible polymers is becoming increasingly important and hence a representative study of a polycarbonate/high density polyethylene (PC/HDPE) system is the focus of this paper. A grafted copolymer PC‐graft‐ethylene‐co‐acrylic acid (PC‐graft‐EAA) was generated as a compatibilizer in situ during processing operation by ester and acid reaction between PC and ethylene‐acrylic acid (EAA) in the presence of the catalyst dibutyl tin oxide (DBTO). As the polyethylene (PE) matrix does not play any part during the synthesis of the copolymer and since PC and EAA are also immiscible, to simplify the system, the influence of this copolymer formation at the interface between PC and EAA on rheological properties, phase morphology, and crystallization behavior for EAA/PC binary blends was first studied. The equilibrium torque increased with the DBTO content increasing in EAA/PC blends on Haake torque rheometer, indicating the in situ formation of the graft copolymer. Scanning electron microscopy (SEM) studies of cryogenically fractured surfaces showed a significant change at the distribution and dispersion of the dispersed phase in the presence of DBTO, compared with the EAA/PC blend without the catalyst. Differential scanning calorimetry (DSC) studies suggested that the heat of fusion of the EAA phase in PC/EAA blends with or without DBTO reduced with the formation of the copolymer compared with pure EAA. Then morphological studies and crystallization behavior of the uncompatibilized and compatibilized blends of PC/PE were studied as functions of EAA phase concentration and DBTO content. Morphological observations in PC/PE blends also revealed that on increasing the EAA content or adding the catalyst DBTO, the number of microvoids was reduced and the interface was intensive as compared to the uncompatibilized PC/PE blends. Crystallization studies indicated that PE crystallized at its bulk crystallization temperature. The degree of crystallinity of PE phase in PC/PE/EAA blends was also reduced with the addition of EAA and DBTO compared to the uncompatibilized blends of PC/PE, indicating the decrease in the degree of crystallinity was more in the presence of PC‐graft‐EAA. Copyright © 2007 John Wiley & Sons, Ltd.     

Structure elucidation and complete NMR spectral assignments of a new taxane glycoside from the needles of Taxus cuspidata

A new taxane glycoside was isolated from a methanol extract of the needles of Taxus cuspidata. The structure was established as 2alpha,9alpha,10beta-triacetoxytaxa-4(20),11-dien-13-one-5alpha-O-beta-D-glucopyranoside (1) on the basis of 1D- and 2D NMR and high-resolution fast atom bombardment mass spectral analyses.     

Antioxidative effects of flavonols and their glycosides against the free-radical-induced peroxidation of linoleic acid in solution and in micelles

The antioxidative effect of flavonols and their glycosides against the peroxidation of linoleic acid has been studied in homogeneous solution (tBuOH/H(2)O, 3:2) and in sodium dodecyl sulfate and cetyl trimethylammonium bromide micelles. The peroxidation was initiated thermally by the water-soluble initiator 2,2'-azobis(2-methylpropionamidine) dihydrochloride, and the reaction kinetics were studied by monitoring the formation of linoleic acid hydroperoxides. The synergistic antioxidant effect of the flavonols with alpha-tocopherol (vitamin E) was also studied by following the decay kinetics of alpha-tocopherol and the alpha-tocopheroxyl radical. Kinetic analysis of the antioxidative process demonstrates that the flavonols are effective antioxidants in solution and in micelles, either alone or in combination with alpha-tocopherol. The antioxidative action involves trapping the initiating radicals in solution or in the bulk-water phase of the micelles, trapping the propagating lipid peroxyl radicals on the surface of the micelles, and regenerating alpha-tocopherol by reducing the alpha-tocopheroxyl radical. It was found that the antioxidant activity of the flavonols and their glycosides depends significantly on the position and number of the hydroxy groups, the oxidation potential of the molecule, and the reaction medium. The flavonols bearing ortho-dihydroxy groups possess significantly higher antioxidative activity than those without such functionalities, and the glycosides are less active than their parent aglycones. The activity of the flavonols is higher in micelles than in solution, while the activity of alpha-tocopherol is lower in micelles than in solution. This is because the predominant factor for controlling the activity is the hydrogen-bonding interaction of the antioxidant with the micellar surface in the case of hydrophilic flavonols, while it is the inter- and intramicellar diffusion in the case of lipophilic alpha-tocopherol.     

Simultaneous determination of noradrenaline and dopamine in Portulaca oleracea L. by capillary zone electrophoresis

A simple and rapid capillary electrophoretic method was developed for the simultaneous determination of noradrenaline (NA) and dopamine (DA) in Portulaca oleracea L. The buffer solution used in this method was 40 mM tris (hydroxymethyl) aminomethane (Tris)-H3PO4 at pH 2.00 containing 15% methanol. The effects of pH value, organic modifier, and applied voltage were investigated. The linear ranges of NA and DA were 0.5-100 microg/mL (r=0.9952) and 6.25-200 microg/mL (r=0.9992), respectively. The relative standard deviations of the corrected peak area were 6.73% and 4.26%, respectively. NA and DA in Portulaca oleracea L. were simultaneous determined successfully within 5.6 min. In this way, the contents of NA and DA in different parts (stem, leaves, and seeds) of P. oleracea L. and in different extracts of leaves with different solvents (distilled water, 50% methanol, and methanol) were studied.     

Determination of Total Reduced Thiol Levels in Plasma Using a Bromide Substituted Quinone

The exploitation of 2‐bromo‐1,4‐naphthoquinone (NQBr) as a selective redox label for the determination of reduced thiol functionalities (RSH) has been investigated. The system is selective for RSH functionality, giving distinct voltammetric signals for glutathione and cysteine but can also be adapted for broad spectrum thiol detection. Ion chromatographic protocols based on conductimetric detection enable total RSH analysis (protein and monomolecular moieties) within human plasma. Bromide released through the reaction can be easily quantified and integrated within normal IC measurements. The efficacy of the approach has been assessed and the response validated through comparison with the standard colorimetric technique.     

Synthesis, Crystal Structure and Properties of [Co(1,3- bdoaH)_2·4H_2O]·4H_2O with Benzene-1,3-dioxyacetate Ligand

1INTRODUCTIONTheorganicaromaticcarboxylatemetalcom-plexeshavearousedmuchattentionandbeenwidelyinvestigated.However,thestrategyofdesignandsynthesisofthesecomplexesismostlyfocusedonrigidligands,suchasterephthalicacidandbenzenetricarboxylicacid,etc.[1～5].Theassemblyofcom-plexesbyusingflexiblearomaticcarboxylateli-gandsisfarlessdeveloped[6,.Phenylenedioxydia-7]ceticacids(bdoaH2)withbiologicalactivitiesandwideapplicationsinagriculture[8]areafamilyofmultidentateflexibleligandswithversatilebind…     

The Purification of Glucose Type Glycosyl Nitrate and the Synthesis of Spacer—armed N—Acetyllactosamines and Their Dimers

Our previous paper1,2reported the results of selective synthesis of mannose type glycosides and their dimers in our attempt to synthesize derivatives of N-acetyllacto- samine, which could have potential activity of anti-metastasis3. Further studies on the glycosylation of the accepters exploiting glycosyl nitrate instead of the acetate as donor showed interesting chemoselectivity between the two kinds of donor, namely, the glucose type and the mannose type. The reactivity difference of the t…     

3-对甲苯基-5-(4′-硝基-2′-羧基苯偶氮)-2-硫代-4-噻唑啉酮的合成及用于铜的荧光光度测定

本文报道了新荧光试剂3-对甲苯基-5-（4’-硝基-2‘-羧基苯偶氮）-2-硫代-4-噻唑啉酮（MPNCPATTN）的合成。通过元素分析、红外光谱，核磁共振氢谱和质谱确证了其结构。在pH5．6时，它与铜（Ⅱ）形成稳定的荧光络合物，在λex／λem=308nm／403nm处产生强烈荧光，其荧光强度与铜（Ⅱ）的浓度在6．28×10－9～9．44×10-7mo1／L范围内呈线性关系，检测限为0.399μg／L的铜（Ⅱ）。测定了人发中的痕量铜，结果满意。     

四溴代邻苯二甲酸根桥联的双核钴（Ⅱ）配合物的合成和表征

合成和表征了４种以四溴代邻苯二甲酸根阴离子（４Ｂｒ－ＰＨＴＨ）桥联、以１，１０－菲咯啉（ｐｈｅｎ），５－硝基－１，１０－菲咯啉（ＮＯ_２－ｐｈｅｎ），２，２′－联吡啶（ｂｐｙ）和４，４′－二甲基－２，２′－联吡啶（Ｍｅ_２ｂｐｙ）端接的双核钴（Ⅱ）配合物［Ｃｏ_２（４Ｂｒ－ＰＨＴＨ）（Ｌ）_４］（ＣｌＯ_４）（Ｌ＝ｐｈｅｎ（ｌ），ＮＯ_２－ｐｈｅｎ（２），ｂｐｙ（３），Ｍｅ_２ｂｐｙ（４））。基于ＩＲ光谱、元素分析、电导测量等方法推定配合物具有四溴代邻苯二甲酸根桥联结构和Ｃｏ（Ⅱ）离子具有畸变的八面体配位环境。进行了配合物变温磁化率（７５～３００Ｋ）的测定，其数据已用从自旋哈密顿符导出的磁方程拟合，求得交换参数Ｊ＝－０．８７ｃｍ~（－１）（１），－０．８４ｃｍ~（－１）（２），－０．８２ｃｍ~（－１）（３），－０．８５ｃｍ~（－１）（４），表明金属离子间有弱的反铁磁性自旋交换相互作用。