Effectiveness of natural and synthetic blocking reagents and their application for detecting food allergens in enzyme-linked immunosorbent assays

Blocking is an important step before an enzyme-linked immunosorbent assay (ELISA) can be performed. It reduces non-specific binding to the microtiter plate to a minimum. For detecting food allergens by means of ELISA, the problem with protein blocking solutions is obvious. The blocker might interfere with the antibodies of the assay and leads to false positive results. Therefore, other blocking solutions are greatly needed. There are some alternatives like synthetic blockers or carbohydrates. Comparisons of these different blocking agents, namely proteins, carbohydrates, and synthetic blockers, were made at different reaction conditions. The incubation periods and temperatures were varied, as well as the pH. The best combinations were evaluated and compared, in respect of their blocking efficiency. The two best non-proteinaceous blockers, i.e. polyvinylalcohol and Ficoll, were subsequently applied to ELISA tests for the determination of α-casein and peanut. The study showed that Ficoll and PVA did as well as BSA in buffer solution. Therefore, they can be considered as alternative blocking reagents for ELISA, especially for the detection of food allergens.     

Improved rapid assay of plasma uric acid by short-end injection capillary zone electrophoresis

A rapid and simple short-end injection capillary zone electrophoresis method was developed for the quantification of plasma uric acid. The separation was performed in an uncoated fused-silica capillary (50 μm ID, 60 cm total length, 10.2 cm effective length) by using as a background electrolyte a 75 mmol/L glycylglycine solution titrated with NaOH 5 mol/L to pH 9.0, a voltage of 28 kV, a cartridge temperature of 15 °C, and direct UV detection at 292 nm. Under optimized conditions, uric acid was determinate in little more than 1 min (1.076 minutes). In order to verify the accuracy of the analysis, urate levels were measured in 543 apparently healthy volunteers by the new assay and our previous method, and the obtained data were compared by Passing–Bablock regression, Bland–Altman test, and a new regression-based approach, which showed a good agreement between two methods.     

Synthesis,Crystal Structure,Ab Initio Studies and Fingerprint Plots of 2-Chloro-1,3-dioxo-2,3-dihydro-1H-inden-2-yl acetate

Abstract  

2-Chloro-1,3-dioxo-2,3-dihydro-1H-inden-2-yl acetate, C₁₁H₇ClO₄ (Fig. 1), has been synthesized and the structure has been solved by IR and X-ray diffraction studies. The crystals are triclinic, space group P [`1] \bar{1} , with a = 7.62060(10) ?, b = 11.5944(2) ?, c = 13.0753(3) ?, α = 97.2820(10)°, β = 101.5740(10)°, γ = 101.7930(10)°, Mr = 238.62, V = 1090.82(3) ?³, Z = 4 and R = 0.0557. In the title compound there are two molecules in the asymmetric unit. The molecules are linked via weak C–H···O hydrogen bonds forming R₄⁴(28) rings. The intermolecular interactions were analysed by means of the fingerprint plots derived from the Hirshfeld surfaces. The fingerprint plots evidenced subtle differences in the intermolecular contacts for the two independent molecules.      

GeO2 natrolite-type infinite four and eight R-containing layers in a 2D pure-Ge framework: Ge3O5(OH)4[C2N2H10

A new two-dimensional framework germanate, Ge3O5(OH)4[C2N2H10] (denoted ICMM-8), with a 3:9 Ge:O ratio has been synthesized, using a mixture of pyridine, water, and ethanol as the solvent and 1,4-diazabicyclo[2.2.2]octane and ethylenediamine as the structure-directing agents, under solvothermal conditions. The structure was determined by single-crystal X-ray diffraction. In this new compound, the GeO2 natrolite-type infinite four and eight R-containing layers appears for the first time in a pure GeO2 framework. The total 2D structure is built up from SBU-6, four tetrahedra, and two octahedra. The hydroxyl groups occupy four positions of each octahedral germanium atom. The compound is characterized by IR spectra and TGA-DTA. Crystal data: Ge3O5(OH)4[C2N2H10], monoclinic space group P2(1)/c; a = 11.3570(9) Angstroms, b = 8.8819(7) Angstroms, c = 9.9200(8) Angstroms, beta = 90.710(1), V = 1000.6(1) Angstroms(3), Z = 4, R(1) = 0.044 (I > 2(I)), and wR(2) = 0.1051 (all data).     

Comparison of stir bar sorptive extraction and membrane-assisted solvent extraction as enrichment techniques for the determination of pesticide and benzo[a]pyrene residues in Brazilian sugarcane juice

The biodegradation of the organophosphorus insecticide methyl parathion (MP) in aqueous environment by bacteria isolated from river sediment has been studied. Two species of bacteria which show strong MP degradation ability are identified as Shewanella and Vibrio parahaemolyticus. The biodegradation of MP proceeded rapidly with the formation of a series of intermediate products, which were analyzed using a combination of GC/MS and HPLC/ESI-TOFMS techniques. The major products tentatively identified include a series of reduced products of MP. Results demonstrate that the coupling of TOFMS to HPLC enhances further the capability of LC-MS in the identification of polar organic species in complex environmental samples. Degradation pathways leading to the formation of these products are proposed which involves first the reduction of nitro to amino group in MP, followed by combination with some intrinsic matters of bacteria. The mechanism and products from biodegradation are quite different from those of photocatalytic process for which the main intermediates included methyl paraoxon and 4-nitrophenol.     

Synthesis, multiphase characterization, and helicity control in chiral DACH-linked oligothiophenes

A new class of chiral oligothiophenes is described. Mono-, bi-, ter-, and quarterthiophenes have been linked to enantiopure trans-1,2-cyclohexanediamine (DACH) via diamino or diimino moieties. The stereochemistry of DACH, the type of linker, and oligothiophene size determine the conformational flexibility of these molecules and consequently their molecular and supramolecular helicity in solution and in the solid state. The case of diaminobis(bithiophene), which inverts helicity and shows chiral amplification in the transition from solution to film, is described in detail. Based on the combined use of circular dichroism in solution and in the solid state, single-crystal/thin-film X-ray diffraction, and polarized optical microscopy, a working mechanism has been proposed to explain this unexpected behavior.     

Data mining by total ranking methods: a case study on optimisation of the "pulp and bleaching" process in the paper industry

Total order ranking methods are multicriteria decision making techniques used for the ranking of various alternatives on the basis of more than one criterion. The criteria, which are the standards by which the elements of the system are judged are not always in agreement, they can be conflicting, motivating the need to find an overall optimum that can deviate from the optima of one or more of the single criteria. Total order ranking methods are based on an aggregation of the criteria in a scalar function, i.e. an order or ranking index, which allow to sort elements according to its numerical value. Several evaluation methods which define a ranking parameter generating a total order ranking have been proposed in the literature. Four total order ranking methods are here described: Desirability functions, Utility functions, Dominance functions and Absolute Reference method. These methods have been compared to each other by applying them to a decision making problem in the paper industry. Various bleaching processes have been analysed and compared on the basis of multiple criteria, the aim being to find out best bleaching process among the ones proposed in the last years as alternative to chlorine bleaching process which is of high environmental impact due to the potential for chlorinated dioxin production.     

Aflatoxin M1 determination in cheese by liquid chromatography-tandem mass spectrometry

A new method for determining aflatoxin M1 (AFM1) in cheese by liquid chromatography-tandem mass spectrometry has been developed. Two methodologies were compared for sample extraction. The first one involves sample extraction with dichloromethane for hard, aged cheese or acetone for fresh cheese and includes a preliminary matrix solid-phase dispersion-extraction step before solid-phase extraction (SPE) clean-up by a Carbograph-4 cartridge. The second method uses a water/methanol solution (90:10, v/v) extraction at 150 degrees C before clean-up. The average recoveries of AFM1 from samples spiked at levels of 0.25-0.45 microg/kg, were 81-92% and the precision (RSD) ranged from 3 to 7% with the first method, whilst the average recoveries were 79-84%, and RSD ranged from 7 to 15% for the second method. Due to different matrix effect, the quantification limits were 0.019-0.025 microg/kg in the first case and 0.048-0.143 microg/kg in the second one, depending on cheese typology.     

Structure-property relationships in push-pull amino/cyanovinyl end-capped oligothiophenes: quantum chemical and experimental studies

A series of push-pull chromophores built around thiophene-based pi-conjugating spacers and bearing various types of amino donors and cyanovinyl acceptors have been analyzed by means of UV-vis-NIR, IR, and Raman spectroscopic measurements in the solid state as well as in solution. The intramolecular charge transfer (ICT) of these pi-conjugated systems has also been tested by analyzing the ability of the solute molecules to undergo shifts in their fluorescence emission maxima with increasing solvent polarity. These push-pull oligomers also display an attractive electrochemical behavior since they generate stable species both upon oxidation and reduction. Oxidation mainly involves changes in the electron-rich aminooligothienyl half-part of the molecule and leads to the formation of stable cations. On the other hand, reduction to radical anions and dianions is mainly cyanovinyl-centered but also affects the pi-conjugated electron relay. Density functional theory (DFT) calculations have been carried out to help the assignment of the most relevant electronic and vibrational features and to derive useful information about the molecular structure of these NLO-phores.