Analysis of the Lipidome of Xenografts Using MALDI-IMS and UHPLC-ESI-QTOF

Human tumor xenografts in immunodeficient mice are a very popular model to study the development of cancer and to test new drug candidates. Among the parameters analyzed are the variations in the lipid composition, as they are good indicators of changes in the cellular metabolism. Here, we present a study on the distribution of lipids in xenografts of NCI-H1975 human lung cancer cells, using MALDI imaging mass spectrometry and UHPLC-ESI-QTOF. The identification of lipids directly from the tissue by MALDI was aided by the comparison with identification using ESI ionization in lipid extracts from the same xenografts. Lipids belonging to PCs, PIs, SMs, DAG, TAG, PS, PA, and PG classes were identified and their distribution over the xenograft was determined. Three areas were identified in the xenograft, corresponding to cells in different metabolic stages and to a layer of adipose tissue that covers the xenograft.

Comparison of triple quadrupole mass spectrometry and Orbitrap high‐resolution mass spectrometry in ultrahigh performance liquid chromatography for the determination of veterinary drugs in sewage: benefits and drawbacks

This paper presents a comparison of triple quadrupole tandem mass spectrometry (MS/MS) and Orbitrap high‐resolution mass spectrometry (HRMS) combined to ultrahigh performance liquid chromatography for the determination of glucocorticoids and polyether ionophores in sewage, in order to show the major benefits and drawbacks for each mass spectrometry analyser. Overall, HRMS measurements have enhanced performance in terms of confirmatory capabilities than MS/MS measurements. Moreover, similar limits of quantification, limits of detection, linear range and repeatability for glucocorticoids with both the MS/MS and HRMS methods were compared, but in the case of polyether ionophores, slightly better limits of detection and limits of quantification were obtained with the HRMS method because of the high sensitivity obtained when diagnostic ions are used for quantification instead of selected reaction monitoring transitions for these compounds. The two methods have been applied to the analysis of several influent and effluent sewage samples from sewage treatment plants located in the Tarragona region (Catalonia, Spain), showing an excellent correlation between the two methods. Copyright © 2014 John Wiley & Sons, Ltd.     

Flammability and morphology of HDPE/clay nanocomposites

High-density polyethylene/modified bentonite clay/polar compatibilizer nanocomposites were prepared through the melt intercalation process. The clay was organophilizated using different percentages of quaternary ammonium salt 100, 125, and 150 % based cation exchange capacity of the clay. The nanocomposites were prepared in a counter-rotating twin-screw extruder and then specimens were injection molded. For the evaluation of flammability of the test system was used for burning in the horizontal position according to the norm (Underwriters Laboratories, UL94HB) and to the method of cone calorimeter. The thermal behavior of nanocomposites was evaluated by thermogravimetry and X-ray diffraction techniques, and transmission electron microscopy were used to characterize the morphology and analyze the degree of expansion of the clays prepared and the degree of exfoliation of nanocomposites. It was observed that the percentage of ammonium salt and the compatibilizer polar influence on the final properties of the systems and consequently improving the thermal stability and reducing the flammability of the matrix.     

Characterization of Pentaclethra macroloba oil

The Pracaxi oil—(Pentaclethra macroloba) contains high concentrations of fatty acids with emollient action that contribute to skin hydration. The use of this oil is supported by the utilization of natural resources thus enabling regional development and social contribution. The objective of this study was to characterize the P. macroloba oil by thermogravimetry (TG, DTG, and DTA), gas chromatography, Fourier transform infrared spectroscopy (FT-IR), and oxidation stability—Rancimat, aiming at the quality control of plant raw material. Three samples of crude oil sold by Amazon Oil Industry (Ananindeua, Pará, Brazil) were studied. The analysis of these oil samples showed different fatty acids, especially the behenic, oleic, linoleic, and lignoceric acids totalizing approximately 96 % of the grease composition and in smaller percentage arachidic, lauric, myristic, palmitic, and linolenic acids were found. The major acids have wide medicinal use. According to the TG/DTG curve, thermal stability was observed up to 220 °C, indicating a greater mass loss related to the dehydration and elimination of volatile substances. The thermal decomposition process occurred in the range of 430–450° C according to the DTG curve. The absorption spectrum in the infrared region (FT-IR) showed well-defined bands confirming the presence of functional groups present in the oil. Tests in a Rancimat have shown an induction period between 8 and 10 h demonstrating that the samples are in agreement with the standards required by ANP No. 14/2012 which requires at least 6 h of testing.     

Thermal analysis of polyaniline poly(N-vinylpyrrolidone)-stabilized dispersions

The polyaniline dispersions stabilized with poly(N-vinylpyrrolidone) (PANI/PVP) were synthesized by oxidative polymerization with different mass ratios of PANI and PVP and different molar concentrations of the components in the polymerization mixture. The composite powders prepared from colloidal PANI/PVP dispersions were characterized by thermogravimetry and differential thermal analysis. The change in the ratio of PANI and PVP as well as the starting molar concentrations of aniline hydrochloride and oxidant has influence on the resulting properties of the dispersions. Concerning the doping, the results show that PANI/PVP powders are stable up to approximately 160 °C. Degradation of polymer chains starts at temperatures above 250 °C. The PANI/PVP composite powders with lower content of PANI exhibit slightly higher thermal stability. Further, colloidal PANI/PVP dispersions were screen-printed on aluminum foil for infrared spectroscopic characterization and on poly(ethylene terephthalate) foil for electrical measurements. The sheet resistance of printed layers measured by two-point probe was of the order of tens to thousands of kΩ sq^?1. The influence of both the change in the composition and the drying temperature is discussed.     

Development of a calorimetric sensor for medical application

A calorimetric sensor has been developed for local and direct measurement of calorific dissipations in different parts of the human body. The constructed prototype has a detection surface of 36 cm². In this paper, a deconvolution method is proposed to reconstruct the dissipated power. The advantage of this method is that: to determine the dissipated power, it is not necessary to correct the baselines to calculate either the areas of the calorimetric signal or that of the dissipated power in the temperature control because the proposed method takes into account, apart from the calorimetric signal, the thermostat temperature and the ambient temperature.     

Chemical Synthesis, 3D Structure,and ASIC Binding Site of the Toxin Mambalgin‐2

Mambalgins are a novel class of snake venom components that exert potent analgesic effects mediated through the inhibition of acid‐sensing ion channels (ASICs). The 57‐residue polypeptide mambalgin‐2 (Ma‐2) was synthesized by using a combination of solid‐phase peptide synthesis and native chemical ligation. The structure of the synthetic toxin, determined using homonuclear NMR, revealed an unusual three‐finger toxin fold reminiscent of functionally unrelated snake toxins. Electrophysiological analysis of Ma‐2 on wild‐type and mutant ASIC1a receptors allowed us to identify α‐helix 5, which borders on the functionally critical acidic pocket of the channel, as a major part of the Ma‐2 binding site. This region is also crucial for the interaction of ASIC1a with the spider toxin PcTx1, thus suggesting that the binding sites for these toxins substantially overlap. This work lays the foundation for structure–activity relationship (SAR) studies and further development of this promising analgesic peptide.     

Palladium‐Catalysed Direct Cross‐Coupling of Organolithium Reagents with Aryl and Vinyl Triflates

A palladium‐catalysed cross‐coupling of organolithium reagents with aryl and vinyl triflates is presented. The reaction proceeds at 50 or 70 °C with short reaction times, and the corresponding products are obtained with moderate to high yields, with a variety of alkyl and (hetero)aryl lithium reagents.     

Synthesis and Conformational Analysis of Cyclic Homooligomers from Pyranoid ε‐Sugar Amino Acids

New pyranoid ε‐sugar amino acids were designed as building blocks, in which the carboxylic acid and the amine groups were placed in positions C2 and C3 with respect to the tetrahydropyran oxygen atom. By using standard solution‐phase coupling procedures, cyclic homooligomers containing pyranoid ε‐sugar amino acids were synthesized. Conformation analysis was performed by using NMR spectroscopic experiments, FTIR spectroscopic studies, X‐ray analysis, and a theoretical conformation search. These studies reveal that the presence of a methoxy group in the position C4 of the pyran ring produces an important structural change in the cyclodipeptides. When the methoxy groups are present, the structure collapses through interresidue hydrogen bonds between the oxygen atoms of the pyran ring and the amide protons. However, when the cyclodipeptide lacks the methoxy groups, a U‐shape structure is adopted, in which there is a hydrophilic concave face with four oxygen atoms and two amide protons directed toward the center of the cavity. Additionally, we found important evidence of the key role played by weak electrostatic interactions, such as the five‐membered hydrogen‐bonded pseudocycles (C₅) between the amide protons and the ether oxygen atoms, in the conformation equilibrium of the macrocycles and in the cyclization step of the cyclic tetrapeptides.     

Naphthocrown‐Strapped Calix[4]pyrroles: Formation of Self‐Assembled Structures by Ion‐Pair Recognition

A new approach to the construction of self‐assembled structures is reported that is based on ion‐pair recognition. Towards this end, the calix[4]pyrrole naphthocrown‐4 hybrid structures 2 and 3 were prepared. These multitopic receptors contain recognition sites for both anions and cations. On the basis of solution‐phase ¹H NMR spectroscopic analysis and solid‐state single‐crystal X‐ray diffraction structural studies, it was established that receptors 2 and 3 are able to bind specific ion pairs with high selectivity via different binding modes. In the case of CsF and CsCl, the ion‐pair complexes formed from receptors 2 and 3 were found to self‐assemble to produce either linear supramolecular polymeric crystalline solids or nanotube‐like cyclic hexamers depending on the specific choice of ion pairs and crystallization solvents. Proton NMR studies provided evidence for solution‐phase self‐association in organic media.