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991.
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
992.
Arianna Tocchetti Sonia Maffioli Marianna Iorio Silke Alt Emma Mazzei Cristina Brunati Margherita Sosio Stefano Donadio 《Chemistry & biology》2013,20(8):1067-1077
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993.
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
994.
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
995.
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
996.
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
997.
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
998.
Synthesis of 2,6-diaryl-1,2-dihydropyridines through a 6π-electrocyclization of N-sulfonylazatrienes
The development of an efficient synthetic method toward substituted 1,2-dihydropyridines from cinnamylideneacetophenones is reported. The key intermediates N-sulfonylazatrienes were synthesized through a TiCl4-mediated direct condensation of primary sulfonamides with the substituted (E,E)-cinnamylideneacetophenones. The 6π-electrocyclization of these intermediates, catalyzed by a Lewis acid, selectively afforded the desired products in good yields. 相似文献
999.
Silvia García‐Rubín Carlos Gonzlez‐Rodríguez Cristina García‐Yebra Jesús A. Varela Miguel A. Esteruelas Carlos Sa 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2014,126(7):1872-1875
A new synthetic route to dihydrobiphenylenes has been developed. The process involves a mild RuII‐catalyzed [2+2+2] dimerization of ortho‐alkenylarylacetylenes or its more versatile variant, the Ru‐catalyzed [2+2+2] cycloaddition of ortho‐ethynylstyrenes with alkynes. Mechanistic aspects of this [2+2+2] cycloaddition are discussed. 相似文献
1000.
Analysis of cerebrospinal fluid γ‐aminobutyric acid by capillary electrophoresis with laser‐induced fluorescence detection
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Mercedes Casado Marta Molero Cristina Sierra Angels García‐Cazorla Aida Ormazabal Rafael Artuch 《Electrophoresis》2014,35(8):1181-1187
The measurement of γ‐aminobutyric acid (GABA) is suitable for investigating various neurological disorders. In this study, a sensitive and selective method for free GABA quantification in cerebrospinal fluid (CSF) has been standardised. This method is based on CE with LIF detection using 4‐fluoro‐7‐nitrobenzo‐2‐oxa‐1,3‐diazole (NBD‐F) as a derivatisating agent. The reaction conditions (NBD‐F concentration, pH, temperature and reaction time) and the electrophoretic parameters (run buffer composition and pH and separation voltage) were optimised to obtain the maximum derivatisation efficiency and electrophoretic resolution. The best resolution was obtained using 200 mM sodium borate, 10 mM SDS, 8.5 mM β‐CD, pH 10 and 20 kV voltage. The method was linear in the concentration range of 2.5–1000 nM with good inter‐ and intra‐assay precision values. The effects of CSF handling on free GABA concentrations were also evaluated. Our results show that the time delay between CSF collection and freezing strongly increases the CSF GABA values. Age‐related reference values were established in 55 paediatric controls. The influence of antiepileptic therapy on free CSF GABA was studied in 38 neuropaediatric patients. Significantly, higher GABA values were obtained in patients taking valproic acid or vigabatrin therapy, which are antiepileptic drugs that modulate GABA metabolism. 相似文献