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41.
Carina Schönherr Sounia Touchene Gaston Wilser Regine Peschka-Süss Giancarlo Francese 《Journal of chromatography. A》2009,1216(5):781-786
In recent decades the use of liposomal preparations as drug delivery systems has become very attractive in pharmaceutical development. Therefore, thorough characterization and quantification of the lipids which form liposomes is wished from both investigators and regulatory authorities when the application in humans is being considered. In this study a new HPLC method for the detection of lipids in liposomal formulations was established using corona charged aerosol detection (CAD) which has the advantage to be independent of the chemical properties of the analytes. The superiority of this method over UV detection was demonstrated. Compared to UV detection no absorption effects of the organic solvent in the mobile phase interfering with the lipid signals were observed with CAD. CAD showed good linearity (R2 > 0.990) for all liposomal compounds. The acceptance criteria for precision including repeatability were met. The average recovery for each of the excipients of the liposomal formulation was in the range of 90.0–110%. 相似文献
42.
Carina R. Martins Lucas C. Ducati Cludio F. Tormena Roberto Rittner 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2009,72(5):1089-1096
The conformational isomerism of 2-chlorocyclopentanone and 2-bromocyclopentanone has been determined through the solvent dependence of the 1H NMR 3JHH coupling constants, theoretical calculations and infrared data, using the solvation theory for the treatment of NMR data. In 2-chlorocyclopentanone, the energy difference (EΨ-e − EΨ-a), in the isolated molecule at B3LYP level of theory, between the pseudo-equatorial (Ψ-e) and pseudo-axial (Ψ-a) conformers is 0.42 kcal mol−1, which decreases in CCl4 and in acetonitrile solutions, in good agreement with infrared data (νCO), despite the uncertainties of the latter method. The conformational equilibrium for 2-bromocyclopentanone is also between the Ψ-e and Ψ-a conformations, with an energy difference (EΨ-e − EΨ-a), in the isolated molecule at B3LYP level of theory, is 0.85 kcal mol−1 which decreases in CCl4 and in acetonitrile solutions, also in good agreement with infrared data. 相似文献
43.
Maribel Arroyo Sylvain Bernès Norma Calixto Carina Gómez 《Journal of fluorine chemistry》2006,127(1):22-28
A series of three new trithioether compounds containing fluorinated phenyl moieties, 1,3,5-(CH2SRf)3-2,4,6-(CH3)3C6, Rf = C6F5 (1), 4-HC6F4 (2), or 2-FC6H4 (3), were prepared by treatment of 1,3,5-(CH2Br)3-2,4,6-(CH3)3C6 with the corresponding Pb(SC6F5)2 or NaSRf. The new structures were verified by elemental analyses, IR, 1H NMR, 19F NMR spectroscopies, and mass spectra. The single crystal X-ray diffraction studies of 1-3 show a similar cis,trans,trans-conformation for the three fluorophenylthiomethyl groups attached to the central benzene ring with all dihedral angles between planes of central ring and external rings close to 0°, giving flat molecules. Comparing, 1-3 with closely related tripodal molecules built-up on 2,4,6-trimethylbenzene, arrangement of one SR group respect to others seems to be defined by the nature of the R substituent. Then in the case of 1-3, a parallel arrangement of rings is favored over an orthogonal one, which would bring the ortho-F atoms close to H atoms of the methylene groups. 相似文献
44.
Closed-form solutions for stepped Timoshenko beams with internal singularities and along-axis external supports 总被引:1,自引:0,他引:1
S. Caddemi I. Caliò F. Cannizzaro 《Archive of Applied Mechanics (Ingenieur Archiv)》2013,83(4):559-577
The Timoshenko beam model in presence of internal singularities causing deflection and rotation discontinuities and resting on external concentrated supports along the span is studied in a static context. The internal singularities are modelled as concentrated reductions in the flexural and the shear stiffness by making use of the distribution theory. Along-axis supports are treated as unknown concentrated loads and moments. An exact integration procedure of the proposed model, not requiring continuity conditions at all, is presented. Closed-form solutions are provided for both cases of homogeneous and stepped Timoshenko beams. The so-called static Green’s functions are also obtained by the proposed procedure and their explicit expressions are provided. 相似文献
45.
Summary The propagation of solitary wave trains in the Adriatic Sea is studied by means of LANDSAT Thematic-Mapper images. The baroclinic
Rossby radius of deformation has been estimated from the width of a baroclinic current observed along the coast of Croatia
using AVHRR data. The phase speed of the linear internal waves has been consequently estimated and the compatibility of the
Kortweg-de Vries equations with experimental data has been tested. Satellite-derived wave parameters are in good agreement
with a plane-bottom, shallow-water solitary-wave model. 相似文献
46.
Dr. Christian Pett Dr. Waqas Nasir Dr. Carina Sihlbom M. Sc. Britt‐Marie Olsson M. Sc. Vanessa Caixeta Dr. Manuel Schorlemer Dr. René P. Zahedi Prof. Göran Larson Dr. Jonas Nilsson Prof. Ulrika Westerlind 《Angewandte Chemie (International ed. in English)》2018,57(30):9320-9324
Distinct structural changes of the α2,3/α2,6‐sialic acid glycosidic linkages on glycoproteins are of importance in cancer biology, inflammatory diseases, and virus tropism. Current glycoproteomic methodologies are, however, not amenable toward high‐throughput characterization of sialic acid isomers. To enable such assignments, a mass spectrometry method utilizing synthetic model glycopeptides for the analysis of oxonium ion intensity ratios was developed. This method was successfully applied in large‐scale glycoproteomics, thus allowing the site‐specific structural characterization of sialic acid isomers. 相似文献
47.
Methyl 5-deoxy-5-iodo-pentofuranosides are reductively ring-opened and propargylated in a tandem fashion in the presence of zinc. The 1,7-enynes thus obtained are subjected to ring-closing enyne metathesis with catalyst B to produce functionalized 1-vinyl cyclohexenes. By adding BnNH(2) to the tandem reaction, an amino group can be introduced in the 1,7-enyne products. Addition of 2-TMS-ethynylcerium(III) chloride after the reductive ring-opening produces the corresponding 1,6-enynes. Further annulation of the product 1,3-dienes can be achieved through a Diels-Alder reaction with good control of stereochemistry. These procedures constitute efficient methods for rapid carbocyclization and annulation of carbohydrates to produce a variety of functionalized five- and six-membered ring systems. 相似文献
48.
The influence of [(2-hydroxy-1,1-bis(hydroxymethyl)ethyl)amino]-1-propanesulfonic acid (TAPS) on solutions containing lead(II) was studied by direct current polarography (DCP) and glass electrode potentiometry (GEP). The readings were taken at fixed total TAPS to total lead(II) concentration ratios and various pH values, at 25.0 ± 0.1 °C and ionic strength 0.1 M KNO3.Due to the basic pKa of the ligand, which occurs in the pH range where large amount of lead polynuclear species are formed, and the occurrence of ligand adsorption, that disabled the use of high concentrations of TAPS on DCP experiments, GEP and DCP experimental conditions were put to the limit in order to provide the correct Pb-TAPS-OH model and reliable stability constants.The proposed final model is: PbL, PbL2, PbL2(OH) and PbL2(OH)2 with overall stability constants values, as log β, 3.27 ± 0.06, 6.5 ± 0.1, 12.7 ± 0.1 and 17.27 ± 0.06, respectively.A comparative analysis of the strength of complexation of TAPS and a structural related buffer, 2-hydroxy-3-[tris(hydroxymethyl)methylamino]-1-propanesulfonic acid (TAPSO), with lead is also discussed. 相似文献
49.
Cyclization of N-3 substituted 3-thioureidopropanoic acids in isobutyric anhydride at high temperature resulted in the unexpected formation of N-3,N-1-substituted dihydrouracils, as confirmed by thorough spectroscopic characterization. A mechanism based on the identification of intermediates observed at lower reaction temperatures is proposed. 相似文献