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991.
992.
Luciano Lepori Paolo Gianni Andrea Spanedda Enrico Matteoli 《The Journal of chemical thermodynamics》2011,43(10):1453-1462
Excess molar volumes VE at 298.15 K were determined by means of a vibrating tube densimeter for binary mixtures of {heptane + open chain secondary (diethyl to dibutyl) and tertiary (triethyl to tripentyl) amines} as well as for cyclic imines (C2, C3, C4, C6, and C7) and primary cycloalkylamines (C5, C6, C7, and C12). The VE values were found positive for mixtures involving small size amines, with VE decreasing as the size increases. Negative VE’s were found for tributyl- and tripentylamine, heptamethylenimine, and cyclododecylamine. Mixtures of heptane with cycloheptylamine showed an s-shaped curve.Partial molar volumes of amines at infinite dilution in heptane were obtained from VE and compared with of hydrocarbons and other classes of organic compounds taken from literature. An additivity scheme, based on the intrinsic volume approach, was applied to estimate group (CH3, CH2, CH, C, NH2, NH, N, OH, O, CO, and COO) contributions to . These contributions, the effect of cyclization on , and the limiting slope of the apparent excess molar volumes were discussed in terms of solute–solvent and solute–solute interactions. 相似文献
993.
Cinquanta E Ravagnan L Castelli IE Cataldo F Manini N Onida G Milani P 《The Journal of chemical physics》2011,135(19):194501
We perform a systematic investigation of the resonance and vibrational properties of naphthyl-terminated sp carbon chains (dinaphthylpolyynes) by combined multi-wavelength resonant Raman (MWRR) spectroscopy, ultraviolet-visible spectroscopy, and Fourier-transform infrared (FT-IR) spectroscopy, plus ab initio density functional theory (DFT) calculations. We show that the MWWR and FT-IR spectroscopies are particularly suited to identify chains of different lengths and different terminations, respectively. By DFT calculations, we further extend those findings to sp carbon chains end-capped by other organic structures. The present analysis shows that combined MWRR and FT-IR provide a powerful tool to draw a complete picture of chemically stabilized sp carbon chains. 相似文献
994.
De Leonardis F Pascali G Salvadori PA Watts P Pamme N 《Journal of chromatography. A》2011,1218(29):4714-4719
Microfluidic approaches have demonstrated a relevant impact on radiochemical reactions involving Positron Emission Tomography (PET) nuclides, due to shorter reaction times and smaller precursor quantities. However, little attention has been given to the integration of the initial pre-concentration and drying of radioactive [(18)F]fluoride ions, required for the labeling of radiotracer compounds. In this work we report the design, fabrication and implementation of a glass microfluidic device filled with recyclable anion exchange particles for the repeated recovery of [(18)F] and [(19)F]fluoride ions. The device was first tested with non radioactive [(19)F]fluoride ions and it was shown to repeatedly trap and elute >95% fluoride over 40 successive experimental runs with no decrease in efficiency. The same device was then tested for the trapping and release of [(18)F]fluoride ions over 20 experiments with no measurable decrease in performance. Finally, the [(18)F]fluoride ions were eluted as a K(18)F/K2.2.2 complex, dried by repeated dissolution in acetonitrile and evaporation of residual water, and reacted with ethyl ditosylate (EtDT) leading to the desired product ([(18)F]fluoroethyltosylate) with 96 ± 3% yield (RCY). The overall time needed for conditioning, trapping, elution and regeneration was less than 6 min. This approach will be of great benefit towards an integrated platform able to perform faster and safer radiochemical synthesis on the micro-scale. 相似文献
995.
Donato P Cacciola F Cichello F Russo M Dugo P Mondello L 《Journal of chromatography. A》2011,1218(37):6476-6482
The combined use of the state-of-the-art hybrid mass spectrometers together with high efficient liquid chromatography could surely be a useful tool for such a challenging task, as phospholipids (PLs) analysis. In this research, we used hydrophilic interaction liquid chromatography (150 mm×2.1 mm I.D., 2.7 μm d.p. partially porous column) to achieve the separation of major PLs classes in cow's and donkey's milk samples. Solid-phase extraction (SPE) was performed in order to pre-concentrate minor PLs from non polar lipids (triacylglycerols) and the recovery for the extraction method was assayed on a milk sample, fortified with 5 μg/mL of SM pure standard, and analyzed in triplicate. A value of 89.99% was calculated, with a coefficient of variation (CV%) of 1.93. A 70-min long stepwise gradient of water/acetonitrile afforded baseline separation of PLs classes, at 50 μL/min flow rate. Accurate detection by an ion trap-time of flight (IT-TOF) mass spectrometer (in both positive and negative ionization mode) allowed to fully characterize the distinctive phospholipid profile and fatty acid composition of cow's and donkey's milk, the latter being analyzed for the first time. Evaporative light scattering detection was further employed to attain the quantitative evaluation of major PLs classes identified, by the external calibration method using reference material solutions in the 5-200 μg/mL concentration range. Major difference between the two analyzed samples consisted in the total PLs amount, which in cow's milk was determined as over 20-fold higher than the donkey's. 相似文献
996.
U. Gianfranco Spizzirri Francesca Iemma Francesco Puoci Feng Xue Wei Gao Giuseppe Cirillo Manuela Curcio Ortensia I. Parisi Nevio Picci 《先进技术聚合物》2011,22(12):1705-1712
Novel stimuli‐responsive hydrophilic microspheres were prepared by free radical polymerization of hydroxyethyl methacrylate (HEMA) and methacrylic acid (MA), as hydrophilic monomers, and N‐isopropylacrylamide (NIPAAm) and N,N′‐ethylenebisacrylamide (EBA), as thermo‐sensitive monomer and crosslinker, respectively. Hydrophilic comonomers were introduced in the macromolecular network to synthesize materials with tunable thermal behavior. In addition, by introducing in the polymerization feed both a hydrophilic and a pH‐sensitive monomer, such as MA, dual stimuli‐responsive (pH and temperature) hydrogels were synthesized. The incorporation of monomers in the network was confirmed by infrared spectroscopy, while the network density and the shape of hydrogels was found to strictly depend on the concentration of monomers in the polymerization feed. Thermal analyses showed negative thermo‐responsive behavior with pronounced water affinity of microspheres at a temperature lower than lower critical solution temperature (LCST). In our experiment, the LCST values of the hydrogels were in the range 34.6–37.5°C, close to the body temperature, and the amount of hydrophilic moieties in the polymeric network allows to collect shrinking/swelling transition temperatures higher than the LCST of NIPAAm homopolymers. In order to test the preformed materials as drug carriers, diclofenac diethylammonium salt (DDA) was chosen and drug entrapment percent was determined. Drug release profiles, in media at different temperature and pH, depend on hydrogels crosslinking degree and drug–bead interactions. By using semi‐empirical equations, the release mechanism was extensively studied and the diffusional contribute was evaluated. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
997.
Torvinen M Kalenius E Sansone F Casnati A Jänis J 《Journal of mass spectrometry : JMS》2011,46(8):787-793
The noncovalent complexation of three glucosylcalix[4]arenes (1-3) towards 23 mono- and dicarboxylic acid anions were studied by ESI-FTICR mass spectrometry. Competitive complexation, collision-induced dissociation and gas-phase H/D-exchange experiments were performed to obtain information on selectivity of calixarenes towards carboxylates and characteristics of their complexes. The flexibility and number of glucose units of the host and the spatial disposition of the hydrogen bonding groups on the carboxylate guests were found to affect the selectivity of complexation strongly. The glucosylcalixarenes exhibited particular selectivity for dicarboxylic acid anions incorporating π-systems, and clear isomeric selectivity was observed for isophthalic among phthalic acid anions and for fumaric acid over maleic acid anion. 相似文献
998.
Bortolini O Fantin G Fogagnolo M Giovannini PP Massi A Pacifico S 《Organic & biomolecular chemistry》2011,9(24):8437-8444
An efficient method for the N-heterocyclic carbene (NHC)-catalyzed conjugate addition of acetyl anions to various α,β-unsaturated acceptors (Stetter reaction) has been optimized by using 2,3-butandione (biacetyl) as an alternative surrogate of acetaldehyde. The disclosed procedure proved to be compatible with microwave dielectric heating for reaction time reduction and with the use of different linear α-diketones as acyl anion donors (e.g. 3,4-hexanedione for propionyl anion additions). Moreover, the unprecedented umpolung reactivity of cyclic α-diketones in the atom economic nucleophilic acylation of chalcones is herein presented. Mechanistic aspects of the thiazolium-based catalysis involving linear and cyclic α-diketone substrates are also discussed. 相似文献
999.
Andreasson-Ochsner M Romano G Håkanson M Smith ML Leckband DE Textor M Reimhult E 《Lab on a chip》2011,11(17):2876-2883
Lateral mobility and dimensionality have both been shown to influence cellular behavior, but have yet to be combined and applied in a single in vitro platform to address, e.g., cell adhesion in a setting mimicking the three-dimensional environment of neighboring cells in a reductionist way. To study the effect of the lateral mobility of cell adhesive ligands in three dimensions we present and characterize a platform, which enables patterning of single cells into microwells presenting a cell membrane mimetic interface pre-patterned to its walls. Soluble E-cadherin extracellular domains coupled through an optimized streptavidin-antibody linkage to lipids in a supported lipid bilayer (SPB) were presented on the microwell walls as either laterally mobile or immobile ligands. The fluidity was controlled through a small change in temperature by choosing phospholipids for the SPB with a lipid phase transition temperature around 30 °C. The platform thus enabled the investigation of cell adhesion to either laterally immobile or mobile E-cadherin ligands presented on the same cell membrane mimetic surface. Chinese hamster ovary (CHO) cells engineered to express E-cadherin that were cultured on the platform demonstrated that enhanced cadherin lateral mobility significantly decreased the formation of actin bundles and resulted in more diffuse actin organization, while constraining the cell shape to that of the microwell. This example highlights the potential to use in vitro cell culture platforms to mimic direct cell-cell interaction in a controlled environment that nevertheless captures the dynamic nature of the native cell environment. 相似文献
1000.
Multi-component, regio-selective aldol addition of β-ketoesters to aldehydes: scope and applications
More V Di Mola A Croce G Tedesco C Petronzi C Peduto A De Caprariis P Filosa R Massa A 《Organic & biomolecular chemistry》2011,9(24):8483-8488
Simple and effective multi-component one-pot aldol addition/protection reactions of β-ketoesters to a series of aldehydes in the presence Me(3)SiCl and i-Pr(2)EtN have been described. The analysis of the scope of the reaction revealed a dramatic dependence of the reactivity on the substrates used. Thus the effect of a catalytic amount of DMF and different reaction conditions was widely investigated. Further transformations of the aldol adducts were particularly useful to give valuable diols and compounds with quaternary stereocenters, while X-ray structural analysis gave also important stereochemical information about this challenging reaction. 相似文献