Online UV–visible spectroscopy and multivariate curve resolution as powerful tool for model-free investigation of laccase-catalysed oxidation

The laccase-catalysed transformation of indigo carmine (IC) with and without a redox active mediator was studied using online UV–visible spectroscopy. Deconvolution of the mixture spectra obtained during the reaction was performed on a model-free basis using multivariate curve resolution (MCR). Thereby, the time courses of educts, products, and reaction intermediates involved in the transformation were reconstructed without prior mechanistic assumptions. Furthermore, the spectral signature of a reactive intermediate which could not have been detected by a classical hard-modelling approach was extracted from the chemometric analysis. The findings suggest that the combined use of UV–visible spectroscopy and MCR may lead to unexpectedly deep mechanistic evidence otherwise buried in the experimental data. Thus, although rather an unspecific method, UV–visible spectroscopy can prove useful in the monitoring of chemical reactions when combined with MCR. This offers a wide range of chemists a cheap and readily available, highly sensitive tool for chemical reaction online monitoring.     

掺杂靛红的聚吡咯膜的电色效应

制备了掺杂靛红的聚吡咯（ＰＰｙ）膜修饰电极，这种功能化ＰＰｙ膜电极具有很好的电色效应，其颜色变化明显，响应时间短，稳定性好，是一种新型电色材料。     

紫茉莉花瓣组织全固传感器的研究

利用紫茉莉花瓣研制了对合成食用色素胭脂红选择性响应的新型组织传感器，该传感器灵敏度高，重现性好，选择性好。其线性范围为５×１０＾－３－５×１０＾－７ｍｏｌ／Ｌ，检测下限为２．８×１０＾－８ｍｏｌ／Ｌ；斜率为２０ｍＶ／ＰＣｃａｒ（３０℃，ＰＨ＝５－６）。     

NMR spectroscopic study of the Murex trunculus dyeing process

It is widely accepted that indigo dyes derived from Murex trunculus were used to produce the biblical dyes tekhelet and argaman. We describe a method of following the debromination of natural leucoindigos and their binding to wool using NMR spectroscopy. Debromination is observed prior to reaction with the wool and prior to oxidation. Binding to the wool is shown to occur prior to oxidation. NMR allows the dyeing process to be followed. This, in principle, could be used to correct problems during dyeing that would increase the reliability of the process.     

An Indigo Carmine‐Based Hybrid Nanocomposite with Supramolecular Control of Dye Aggregation and Photobehavior

Zn‐Al layered double hydroxides (LDHs) containing solely indigo carmine (IC) or 1‐hexanesulfonate (HS) anions, or a mixture of the two with different HS/IC molar ratios, were prepared by the direct synthesis method and characterized by various techniques. Hydrotalcite‐type phases were obtained with basal spacings of 17.6 Å for the LDH intercalated by IC (IC‐LDH) and 18.2–18.3 Å for the other materials containing HS. From the basal spacing for IC‐LDH and UV/Vis spectroscopic data, it is proposed that the dye molecules assemble within the interlayer galleries to form a J‐type stacking arrangement. A comprehensive electronic spectral and photophysical study was undertaken for IC in solution and all materials, aiming to obtain a detailed characterization of the host–guest and guest–guest interactions. In solution (the solvent surrounded “isolated” molecule), IC presents a fast excited state proton transfer with rate constants of ～1.2–1.4×10¹¹ s^?1, which is linked to the very efficient radiationless deactivation channel. In the solid state it is shown that incorporation of IC within the LDH decreases the level of aggregation, and that further addition of HS induces the appearance of isolated IC units within the LDH galleries. The indigo carmine‐based nanocomposites reported constitute a step forward in the design of hybrid materials with tunable properties.     

Simultaneous identification of historical pigments Prussian blue and indigo in paintings by electrospray mass spectrometry

A new analytical protocol for identification of Prussian blue (PB) and indigo was proposed. Pigments useful for dating of artworks were detected by flow injection analysis/electrospray ionization mass spectrometry after alkalization of their suspensions in water, decomposition of PB to iron (III) hydroxide and hexacyanoferrate (II) and reduction of indigo to soluble leucoindigo using sodium dithionite. Limits of detection (PB 47 pg, indigo 59 pg) complied with requirements for analysis of microsamples of historical paintings. Potential of the developed method was proven in analysis of blue samples of two oil paintings from the 20^th century. Further, PB was confirmed in a microsample from a painting of ‘Crucifixion’, St. Sebestian church on St. Hill in Mikulov, Czech Republic. Copyright © 2013 John Wiley & Sons, Ltd.     

Catalytic Oxidation of Indigo Carmine in the Presence of Silver Nanoparticles: Application to Groundwater Analysis

The oxidation of indigo carmine by potassium hexacyanoferrate(III) is catalyzed by trace of silver nanoparticle (AgNP). The reaction is followed UV‐Vis absorption spectrophotometrically by measuring the change in the absorption spectra (λ_max 612 nm). The catalytic oxidation reaction is used for the quantification of indigo carmine. The calibration graph was linear in the concentration range 50 nM—1.8 μM of indigo carmine. The variables affecting the method have been optimized. The method is applied to the determination of indigo carmine in groundwater samples with the satisfactory results.     

基于高特异性单克隆抗体的间接竞争ELISA检测食品中胭脂红的研究

该研究设计合成了一种胭脂红半抗原,分别采用重氮化法和戊二醛法将半抗原与载体蛋白偶联制备人工抗原,通过免疫Bal b/c小鼠及杂交瘤技术成功筛选制备了胭脂红高特异性单克隆抗体,与苋菜红、柠檬黄等结构类似物无交叉反应。基于该抗体建立了间接竞争酶联免疫分析方法用于检测食品中胭脂红残留。该方法对胭脂红的半抑制浓度(IC₅₀)和检出限(IC₁₀)分别为10.1 ng/mL和0.98 ng/mL,线性范围为2~50 ng/mL。将该方法应用于山楂条和雪碧中胭脂红的快速检测,样品加标回收率分别为93.0%~113%和93.0%~100%,相对标准偏差分别为9.7%~12%和3.2%~3.9%。结果与HPLC-UV方法一致,表明该方法可用于食品中痕量胭脂红的快速筛查。     

Indigo Carmine as New Label in PNA Biosensor for Detection of Short Sequence of p53 Tumor Suppressor Gene

A new electrochemical PNA hybridization biosensor for detection of a 15‐mer sequence unique to p53 using indigo carmine (IC) as an electrochemical detector is described in this work. This genosensor is based on the hybridization of target oligonucleotide with its complementary probe immobilized on the gold electrode by self‐assembled monolayer formation. Because this label is electroactive in acidic medium, the interaction between IC and short sequence of p53 is studied by differential pulse voltammety (DPV) in 0.1 M H₂SO₄. The results of electrochemical impedance spectroscopy and cyclic voltammetry in the solution of [Fe(CN)₆]^3?/4? shows no breakage in PNA‐DNA duplex. A decrease in the voltammetric peak currents of IC is observed upon hybridization of the probe with the target DNA. The influence of probe concentration on effective discrimination against non‐complementary oligonucleotides is investigated and a concentration of 10^?7 M is selected. The diagnostic performance of the PNA sensor is described and the detection limit is found to be 4.31×10^?12 M.