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971.
M. Fátima Barroso M. João Ramalhosa Cristina Delerue-Matos M. Carmo V.F. Vaz 《International journal of environmental analytical chemistry》2013,93(14):1049-1062
A biochemical gas-sensor (bio-sniffer) was constructed for convenient measurement of odourless hydrogen peroxide (H2O2) vapour, which is harmful to skin and mucous membranes. An enzyme-immobilized membrane was fabricated by spreading the mixture of catalase and photo-crosslinkable polymer on a dialysis membrane. An H2O2 biosensor was constructed by attaching this catalase-immobilized membrane to the sensitive top of a Clark-type oxygen electrode, and the oxygen generation from the decomposition of H2O2 catalysed by catalase was measured amperometrically. This biosensor was first applied to the measurement of H2O2 solution and was able to quantify the concentrations of H2O2 solution from 0.02 to 10.0?mmol?L?1. Then, this biosensor was applied to gaseous phase as a bio-sniffer and was able to detect the odourless H2O2 vapour with the calibration range from 0.5 to 30?ppm, where the threshold limit value assigned by the American Conference of Governmental Industrial Hygienists (1?ppm) is covered. 相似文献
972.
Dan Donescu Raluca Somoghi Catalin Ilie Spataru Doina Manaila-Maximean Denis Mihaela Panaitescu Eugeniu Vasile Cristina L. Nistor 《Colloid and polymer science》2013,291(10):2345-2358
The work describes a study for preparing polystyrene (PSt) and polymethyl methacrylate (PMMA) latex, containing magnetite (Fe3O4), covalently bounded to the polymeric chains. The magnetite was functionalized with various alkoxysilanes containing double bonds: vinyltriethoxysilane (VTES), methacryloyl propyl trimethoxysilane (MPTS) and vinyldimethylethoxysilane (VMe2TES). The ferrite-silane composite forms higher average size particles with MPTS than with VTES. Ferrite functionalized with VMe2TES forms stable latexes with both PSt and PMMA polymers. PSt forms also stable latexes with ferrite functionalized with VTES but unstable with ferrite functionalized with MPTS. 相似文献
973.
Cristina Nerín Elena Canellas Joaquín Romero Ángel Rodriguez 《International journal of environmental analytical chemistry》2013,93(12):863-874
An analytical strategy has been proposed and optimized to study the permeability of several flexible plastic materials, some of them with high-barrier properties, versus naphthalene, methyl bromide, toluene, ethylbenzene, and ortho- and para-xylenes. The strategy involves using a system of concentric plastic bags made from the materials to be tested polyethylene (PE) and used as permeable plastics to facilitate the homogeneous distribution of a solid compound, such as naphthalene, in vapour phase. After the permeation test, the vapour phase containing the pollutants that cross the plastic barrier is trapped in a 12% ethanol–water solution and further analysed by SPME in headspace mode. Several experimental conditions as well as different samples were tested. The results obtained are shown and discussed. 相似文献
974.
Mohammad‐Reza Azani Dr. Alejandro Pérez Paz Cristina Hermosa Dr. Gonzalo Givaja Prof. Dr. Julio Gómez‐Herrero Dr. Rubén Mas‐Ballesté Dr. Felix Zamora Prof. Angel Rubio 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(46):15518-15529
Herein, we provide a systematic theoretical and experimental study of the structural and optical properties of MMX (M=metal, X=halide) chains. The influence of solvent, temperature, and concentration has been analyzed to find suitable parameters for initial building‐block associations in solution. By using density functional calculations, we have computed the dissociation energy of different MMX oligomers (up to the tetramer) in the gas phase. On the basis of these findings, we discuss the most likely disassembly scenario and propose a new interpretation of these compounds. We also calculated the charge redistribution that occurs upon MM+XMMX binding in vacuum. Time‐dependent density functional theory (TDDFT) is used to calculate the UV/visible spectra of different MMX chains up to the tetramer in the gas phase. The implications of these theoretical findings in the analysis of our experiments are discussed in the text. The overall body of data presented suggests a new way of looking at such linear structures. By taking into account these new data, we have been able to isolate single/few MMX chains on mica. 相似文献
975.
Dr. Cristina Domínguez Dr. Benoît Heinrich Dr. Bertrand Donnio Prof. Dr. Silverio Coco Prof. Dr. Pablo Espinet 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(19):5988-5995
Supramolecular mono‐ and dinuclear liquid‐crystalline gold(I) aggregates have been synthesized by means of hydrogen bond interactions of 2,4,6‐triarylamino‐1,3,5‐triazine with thiolate moities of gold metalloacids [Au(PR3)(SC6H4COOH)] or [μ‐(binap){Au(SC6H4COOH)}2], in 1:1 and 2:1 molar ratio, respectively. All of the supramolecular aggregates display a stable columnar hexagonal mesophase (Colh) at room‐temperature. The supramolecular arrangement within the columns consists of the one‐dimensional stacking of triazine units, with the core of the attached metallic thioacid fragments acting as the fourth branch. The phosphine‐containing moieties of the metallic thioacid protrude out in the aliphatic continuum. These complexes do not show metallophilic interactions, but this strategy appears very promising for the future design of room‐temperature LC mesophases containing interacting metallic fragments. 相似文献
976.
Maria Laura Di Lorenzo Maria Cristina Righetti 《Journal of Thermal Analysis and Calorimetry》2013,112(3):1439-1446
Quantitative thermal analysis of the evolution of crystal and amorphous fractions of poly[(R)-3-hydroxybutyrate] (PHB) upon storage at room temperature is detailed in this contribution. Conventional and temperature-modulated calorimetry were used to quantify the crystallinity, as well as the mobile and rigid amorphous fractions, of an initially partially crystallized PHB, subsequently maintained at 25 °C for various times. PHB undergoes progressive crystallization during storage, with an increase in crystal fraction (w C) from the initial w C = 0.35 up to w C = 0.71 attained after 1 year of storage. Crystallization is accompanied by vitrification of rigid amorphous segments, which leads to a noteworthy increase of the overall fraction of the material that is solid at room temperature, leaving only a mobile amorphous fraction w A = 0.04 after 1 year at 25 °C. The quantitative thermal analysis allowed to clarify the kinetics of evolution of both the ordered and unordered fractions of PHB upon storage, which leads to a severe deterioration of material’s properties. 相似文献
977.
Catenacci Laura Sorrenti Milena Bruni Giovanna Bonferoni Maria Cristina Sandri Giuseppina Bettinetti Giampiero 《Journal of Thermal Analysis and Calorimetry》2013,111(3):2149-2155
The aim of this study is the solid-state characterization of solid lipid nanoparticles (SLN) based on Compritol® 888 (C888) and Lutrol® F68 (F68), loaded with silver sulfadiazine (AgSD), used to develop sponge-like dressings to treat chronic skin ulcers such as decubitis and leg ulcers. Silver compounds like AgSD, in fact, are used to prevent and/or to treat wound colonization that could impair healing, also in the case of antibiotic-resistant bacteria. Thermal analysis, with support from powder X-ray diffractometry and Fourier transform infrared spectroscopy, is used to characterize lipid and drug bulk, unloaded and drug-loaded SLN. In particular, differential scanning calorimetry is used to investigate the degree of crystallinity and the solid-state modification of lipid, two parameters correlated to drug incorporation and drug release rates. The solid-state characterization demonstrates AgSD entrapment in C888 as a core enclosed into F68 shell. AgSD SLN are also stored at different temperatures 25 and 37 °C, respectively, to study the effect of storage conditions, that induce an increase of the lipid crystallinity index correlated to drug release from the lipid matrix. 相似文献
978.
Dr. Cristina M. Posadas Dr. Nuria Rendón Dr. Joaquín López‐Serrano Dr. Yohar A. Hernández Dr. Eleuterio Álvarez Prof. Dr. Margarita Paneque Prof. Dr. Manuel L. Poveda 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(5):1796-1809
The bis(ethylene) IrI complex [TpIr(C2H4)2] ( 1 ; Tp=hydrotris(3,5‐dimethylpyrazolyl)borate) reacts with two equivalents of aromatic or aliphatic aldehydes in the presence of one equivalent of dimethyl acetylenedicarboxylate (DMAD) with ultimate formation of hydride iridafurans of the formula [TpIr(H){C(R1)?C(R2)C(R3)O }] (R1=R2=CO2Me; R3=alkyl, aryl; 3 ). Several intermediates have been observed in the course of the reaction. It is proposed that the key step of metallacycle formation is a C? C coupling process in the undetected IrI species [TpIr{η1‐O‐R3C(?O)H}(DMAD)] ( A ) to give the trigonal‐bipyramidal 16 e? IrIII intermediates [TpIr{C(CO2Me)?C(CO2Me)C(R3)(H)O }] ( C ), which have been trapped by NCMe to afford the adducts 11 (R3=Ar). If a second aldehyde acts as the trapping reagent for these species, this ligand acts as a shuttle in transfering a hydrogen atom from the γ‐ to the α‐carbon atom of the iridacycle through the formation of an alkoxide group. Methyl propiolate (MP) can be used instead of DMAD to regioselectively afford the related iridafurans. These reactions have also been studied by DFT calculations. 相似文献
979.
Cosima D. Calvano Cristina De Ceglie Antonella Aresta Laura A. Facchini Carlo G. Zambonin 《Analytical and bioanalytical chemistry》2013,405(5):1641-1649
In the dairy industry one of the most common frauds is mixing high-value milk (sheep’s and goats’) with milk of lower value (cows’). This illegal practice has commercial, ethical, and serious sanitary consequences because consumers can be exposed to hidden allergens contained in the undeclared cows’ milk. Here, we investigated the possibility of using matrix-assisted laser-desorption/ionization (MALDI)-time of flight (TOF) mass spectrometry (MS) as a rapid, sensitive, and accurate technique for detection of milk adulteration by analysis of phospholipid profiles. Lipid extracts of pure raw milk, commercial milk, and binary mixtures of cows’ and goats’ milk and cows’ and sheep’s milk (the concentrations of each milk varied from 0 % to 50 %) were analyzed with α-cyano-4-chlorocinnamic acid as matrix. The abundance ratio of the ions at m/z 703 and m/z 706 was found to be species-correlated and was used as marker of cows’ milk in sheep’s and goats’ milk. Furthermore, the procedure could potentially be applied to cheese samples, because peaks at m/z 703 and 706 were also found in several commercial cheese samples. This approach proved to be an efficient, rapid, and inexpensive method of detecting milk fraud. Figure
MALDI-TOF MS analysis of intact phospholipid in milk mixtures 相似文献
980.
A comparison of four protocols for the immobilization of an aptamer on graphite composite electrodes
We have performed a comparative study on four protocols for the immobilization of the thrombin aptamer on a graphite-epoxy composite electrode with the aim to identify the most practical method for designing the corresponding impedimetric aptasensor. The protocols included (a) physical adsorption, (b) avidin-biotin affinity interaction, (c) electrochemical activation and covalent bonding via amide groups, and (d) electrochemical grafting using 4-carboxybenzenediazonium coupling. The properties of the sensing surface were probed by electrochemical impedance measurements in the presence of the (ferri/ferro)hexacyanide redox couple. An increase in the interfacial charge transfer resistance (Rct) was noted in all cases after the aptamer-thrombin interaction had occurred. The selectivity of the aptasensor over common serum proteins was also systematically investigated. Physical adsorption resulted in the lowest detection limit of the probe (4.5 pM), while avidin-biotin interaction resulted in highest selectivity and reproducibility exhibiting a 4.9 % relative standard deviation at pM thrombin concentration levels. Figure
The study and comparison of four protocols for the immobilization of a DNA aptamer is reported to detect thrombin onto a graphite-epoxy composite electrode and with use of Electrochemical Impedance spectroscopy as the detection technique. 相似文献