高灵敏显色剂卟啉化合物的研究现状

本文对自1979年以来卟啉化合物作为光度显色剂的应用情况作了总结。着重就灵敏度、选择性、反应速度、实际分析中的应用、晚近进展以及发展前景等问题作了较详细的讨论。     

Analysis of tea components by high-performance liquid chromatography and high-performance capillary electrophoresis

Tea is one of the most popular beverages in the world. The number of reports on the analysis of tea components, especially for catechins, has recently been increasing. We review the recent reports on the analysis of tea components using the analytical methods of high-performance liquid chromatography and high-performance capillary electrophoresis.     

The solid-state E/Z-photoisomerization of 1,2-dibenzoylethene

The E/Z-photoisomerization of trans-1,2-dibenzoylethene (DBE) in the confinement of its crystal lattice proceeds readily, but not as a single crystal to single crystal process which was claimed previously by others. This model for the Z-->E isomerization at the 11-12 double bond of the retinal moiety in the crystal-like confinement of rhodopsin was investigated in view of the fact that the precise geometric features are crucial for a better understanding of the postulated twist mechanism. Atomic force microscopy (AFM) monitored long-range anisotropic molecular movements if trans-DBE was photoisomerized, but cis-DBE was unreactive even at the extreme sensitivity of AFM. The crystal lattices of both isomers cannot accommodate a rotational mechanism but at best the twist mechanism with the large groups not leaving their planes. The unidirectional solid-state photochemistry derives from the crystal packing of cis-DBE which exhibits severe 3D-interlocking. Thus, trans-DBE molecules are not formed in the cis-lattice, because their moving away would be prohibited. Conversely, photochemically formed cis-DBE molecules escape the foreign trans-DBE lattice easily along its glide planes, as is experimentally observed by AFM. These findings are reminiscent of the escape of 11-trans-retinal from the rhodopsin array in the vision cascade.     

肠内营养制剂对短肠综合征大鼠的脂肪吸收与血清游离脂肪酸谱的影响

用气相色谱研究了含长链混合50%中链甘油三脂（MCT/LCT）和长链甘油三脂添加L-精氨酸（Arg/LCT）肠内营养制剂对短肠综合征（SBS）大鼠脂肪吸收、血清游离脂肪酸谱和肠形态的影响。将28只Sprague-Dawley大鼠随机分为四组：小肠离断再吻合并给予LCT营养支持的假手术对照组和分别用LCT、MCT/LCT与Arg/LCT营养支持的85%肠切除组。SBS大鼠显示脂肪吸收的减弱，中链甘油三脂可增强脂肪吸收。含L-精氨酸的肠营养也可增强脂肪吸收，这与其对残余小肠黏膜的向肠促进效应有关。LCT 组显示游离脂肪酸总量的不足，并降低必需的脂肪酸含量。而其它两组的营养状况则得到改善。     

Oxygen uptake photosensitized by disorganized chlorophyll in model systems and thylakoids of greening barley

Light-dependent oxygen uptake was observed and studied in thylakoids from early greening barley in comparison to oxygen uptake in chlorophyll solutions and in thylakoids from fully green leaves. Substantial oxygen uptake was observed in chlorophyll solutions supplemented with tryptophan, histidine, ascorbic acid or linoleic acid. This uptake was diminished by adding azide, beta-carotene and alpha-tocopherol, which are specific singlet-oxygen quenchers. Illuminated thylakoids from greening barley also exhibited marked oxygen uptake that, likewise, was strongly quenched by azide. In comparison, azide was found not to affect oxygen uptake that is associated with the methyl viologen-catalyzed Mehler reaction. It is reasoned that in the first two cases the oxygen uptake arises from chlorophyll-photosensitized activation of oxygen to the singlet state and its consumption by exogenous or endogenous substrates. In greening, we propose that disorganized chlorophyll photo-sensitizes the oxygen uptake.     

Odd/even effect in the chain length on the enthalpy of micellization of gemini surfactants in aqueous solution

The micellization properties of cationic symmetric gemini surfactants, [CmH(2m+1)(CH3)2N(CH2)6N(CH3)2CmH(2m+1)]Br2 (designated as CmC6CmBr2, with m = 7, 8, 9, 10, 11, 12, and 16), has been investigated by isothermal titration microcalorimetry. The critical micelle concentration (CMC) and enthalpy of micellization (DeltaHmic) were determined from calorimetric titration curves. The linear decreasing of log CMC with increasing the length of the hydrophobic chain is consistent with an increase in the hydrophobicity of the alkyl chain. Interestingly, with increasing the length of the alkyl chain, the DeltaHmic values of the surfactants with even numbered alkyl chains vary from endothermic to exothermic, whereas the DeltaHmic values of the surfactants with odd numbered alkyl chains are all endothermic and tend to become more endothermic. The pronounced even/odd effect in DeltaHmic is discussed with respect to the "donor-acceptor" interaction.     

Titrimetric estimation of phosphate, molybdate, tungstate and sulphate with lead nitrate solution, using 1,2-naphthoquinone-2-semicarbazone-4-sulphonic acid (NQS-4S) and 1,2-naphthoquinone-2-thiosemicarbazone-4-sulphonic acid (NQTS-4S) as visual indicators

The use of 1,2-naphthoquinone-2-semicarbazone-4-sulphonic acid and 1,2-naphtho-quinone-2-thiosemicarbazone-4-sulphoic acid as indicators in the titrimetric estimation of phosphate, molybdate, tungstate and sulphate with lead has been examined. The precision, accuracy and applicability of the methods have been evaluated.     

The kinetics of oxidation of selenosemicarbazide by oxygen in the presence of cupric ions

In acidic medium selenosemicarbazide undergoes oxidation by oxygen, dissolved in water, in the presence of copper(II) as a catalyst. The oxidation product exhibits an activating effect. The kinetics of the reaction have been investigated and the kinetic equations deduced both for small and high concentrations of the oxidation product. The constants involved in the kinetic equations deduced have been calculated. The proposed mechanism of the reaction agrees with the experimental results. The oxidation product is supposed to be the bis-selenosemicarbazidinium cation. The postulation of formation of this cation is based on the electronic structure and reactivity of selenosemicarbazide. The reaction can be used for copper determination.     

Carbohydrate-protein interactions at interfaces: comparison of the binding of Ricinus communis lectin to two series of synthetic glycolipids using surface plasmon resonance studies

Two C-lactosyl lipids and the related C-galactosyl lipids have been synthesised and their binding to RCA120 plant lectin was compared with a second series of thiolactosylethoxyalkanes. The interactions were measured quantitatively in real time by surface plasmon resonance (BIAcore) at a range of concentrations and temperatures from 5 to 30 degrees C. The C-galactosyl lipid (1,3-dimethyl-5-[beta-D-galactopyranosyl]-5-(4-octadecyloxybenzyl)pyrimidine-2,4,6-trione) bound much more weakly with a K(A) = 8.86 x 10(5) than the corresponding C-lactosyl lipid (1,3-dimethyl-5-[beta-D-galactopyranosyl-(1 --> 4)-beta-D-glucopyranosyl]-5-(4-octadecyloxybenzyl)pyrimidine-2,4,6-trione) (K(A) = 2.31 x 10(7)). The influence of the linker region of the two different series of lactosyl lipids was clearly demonstrated by the differences in the binding to RCA120 lectin. The changes in kinetic values and in the enthalpic and entropic contribution to the free energy of binding reflected the importance of the linker and the hydrocarbon anchor holding the synthetic glycolipids in the neomembrane.     

Liposomes as signal amplification reagents for bioassays in microfluidic channels

Liposomes with encapsulated carboxyfluorescein were used in an affinity-based assay to provide signal amplification for small-volume fluorescence measurements. Microfluidic channels were fabricated by imprinting in a plastic substrate material, poly(ethylene terephthalate glycol) (PETG), using a silicon template imprinting tool. Streptavidin was linked to the surface through biotinylated-protein for effective immobilization with minimal nonspecific adsorption of the liposome reagent. Lipids derivatized with biotin were incorporated into the liposome membrane to make the liposomes reactive for affinity assays. Specific binding of the liposomes to microchannel walls, dependence of binding on incubation time, and nonspecific adsorption of the liposome reagent were evaluated. The results of a competitive assay employing liposomes in the microchannels are presented.