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991.
In the tetraalkylation of p-tert-butyl[3.1.3.1]homooxacalixarene with BrCH2CO2R and K2CO3 in acetone, the initially formed cone conformer is converted into the more stable 1,4-alternate conformer when R = Me or Et, but not when R = i-Pr or t-Bu. In the case of R = i-Pr, derivatives in fixed 1,4-alternate conformation and in partial cone conformation were also isolated. Compounds in fixed cone conformation are good ligands for tetramethylammonium, acetylcholine, and N-methylpyridinium salts in CDCl3, but the partial cone isomer proved to be somewhat better and even the 1,4-alternate conformer turned out to be active. The possible involvement of the ester functions as additional binding sites is discussed; moreover, an insight into the energetics of the complexation and conformational isomerization processes is given. 相似文献
992.
A method for pharmacokinetic studies using cassette dosing associated with serial bleeding in mice is described. PK profiles of four soluble epoxide hydrolase inhibitors were determined following oral, subcutaneous or intraperitoneal administration individually or in cassette dosing. Parent analyses were performed on only 5 μL of whole blood from serial bleeds (up to 10 per animal), by LC/MS/MS. An accuracy (88-100%) and precision (<10% RSD) were observed, leading to reliable datum points for PK calculation. PK profiles, Tmax, Cmax and half-life values after cassette dosing were similar to the individual PK results. This method dramatically increases speed of data collection while dramatically reducing cost and animal usage. The results presented here clearly indicate that this proposed method could be applicable to high-throughput PK studies. 相似文献
993.
Oliveira MM Castro EG Canestraro CD Zanchet D Ugarte D Roman LS Zarbin AJ 《The journal of physical chemistry. B》2006,110(34):17063-17069
Novel silver nanoparticles/polyaniline composites were obtained through a two-phase water/toluene interfacial reaction. We show that by rigorously controlling the reaction time, different structures of the nanocomposites can be obtained, such as a thin sheet of polyaniline around the silver nanoparticles or a polymer mass with nanoparticles homogeneously embedded within it. Samples were characterized by FT-IR, UV-vis-NIR and Raman spectroscopy, X-ray diffraction, cyclic voltammetry, TEM, and HRTEM. Conductivity and current-voltage characteristics of the nanocomposites were measured, and the results indicate that different properties result from the different structures in which the nanocomposites were formed. 相似文献
994.
The use of photolinkers (photoactivatable heterobifunctional crosslinkers) is a popular method to attach biomolecules to polymer
surfaces. This study addresses the selection of photolinker and the adjustment of reaction conditions, such as the concentration
of biomolecule applied, and irradiation time. The influence of these variables are investigated for four prominent photolinkers:
ketyl-reactive benzophenone (BP) and anthraquinone (AQ), nitrene-reactive nitrophenyl azide (NPA), and carbene-reactive phenyl-(trifluoromethyl)diazirine
(PTD). The influence of substrate material is discussed, and three different polymers served as representative substrates:
poly(methyl methacrylate) (PMMA), polystyrene (PS), and a cycloolefin copolymer (COC). We compared the overall photolinking
efficiency of all photolinkers with respect to the polymer substrate they are applied to, and we found considerable differences
for certain photolinker/substrate combinations. Of all photolinkers and substrates tested, PTD as photolinker and COC as substrate
showed the highest photolinking efficiencies and fastest reaction times. For this study DNA oligonucleotides were chosen as
a model system of biomolecular probes, and fluorescence detection of DNA microarrays served as method of detection. 相似文献
995.
[reaction: see text] The 1-fluoro-1-haloalkenes undergo Pd-catalyzed Negishi cross-couplings with primary alkylzinc bromides to give multisubstituted fluoroalkenes. The alkylation was trans-selective giving pure Z-fluoroalkenes in most cases. The highest yields were obtained with Pd2(dba)3 and PdCl2(dppb) catalysts but the best stereochemical outcome was obtained with less reactive Pd(PPh3)4. The tertiary alkylzincs also produced desired fluoroalkenes in high yields. Coupling of beta,beta-dichlorostyrene with organozinc reagent resulted in the formation of monocoupled product. 相似文献
996.
Gentili A Sergi M Perret D Marchese S Curini R Lisandrin S 《Rapid communications in mass spectrometry : RCM》2006,20(12):1845-1854
Within the European Union the use of anabolic steroids for promoting growth and improving meat-to-fat ratio in food-producing animals has been banned since 1988. For the unequivocal identification of hormone residues in a complex matrix such as meat we have developed a rapid, specific and sensitive liquid chromatography/tandem mass spectrometry (LC/MS/MS) method, in combination with a simple extraction procedure based on the matrix solid-phase dispersion (MSPD). The performances of a triple quadrupole (QqQ) and a quadrupole/time-of-flight (QqTOF) were compared: the QqQ mass spectrometer was found to be more sensitive for almost all studied analytes, but the selectivity was superior using the QqTOF system; the full-scan spectra (acquired without losing sensitivity), mass accuracy and resolution of the hybrid instrument enabled a more probatory analyte identification than that obtained selecting two multiple-reaction monitoring (MRM) transitions with a QqQ. Average recoveries ranged from 80 to 100%, and the detection capabilities (CCbetas) were less than 1.06 ppb with the QqQ instrument and less than 5.20 ppb with the QqTOF instrument for the bovine meat, which proved to be the most complex matrix. 相似文献
997.
Michler's ketone (MK) and tetracyanoethene (TCNE) may be used as a UV-vis probe to investigate the solvent properties of ionic liquids (ILs). In molecular solvents, MK and TCNE give an electron donor-acceptor (EDA) complex, a zwitterionic species or a radical ion pair, depending on the aprotic or protic nature of the solvent and on its ionizing power. In agreement with the behavior observed in aprotic solvents, only the EDA complex was detected in ILs bearing low donor anions (beta < 0.7). The formation constant determined in [bmim][Tf(2)N] (K(c) = 5.6 (0.5) M(-1)) is similar to that measured in 1,2-dichloroethane at 25 degrees C. The visible absorption maximum (nu(max,CTC)) of the EDA complex is quantitatively described by a multiple correlation using the Kamlet-Taft pi, beta, and alpha parameters of the solvents. The H-bond donating capacity of ILs is not sufficient to determine the transformation of the EDA complex into the zwitterionic species, but the Kamlet-Taft alpha parameter seems to affect the position of the absorption band. The high ionization power of ILs, moreover, favors the slow dissociation of the EDA complex into its corresponding radical ion pair; this behavior generally characterizes highly polar and highly ionizing protic solvents, such as TFE and HFI. Finally, since the formation of the EDA complex is strongly affected by the presence of impurities, traces of nucleophiles (chloride or amines) or water may be easily detected through the change of the solution color. 相似文献
998.
999.
Schuster D Laggner C Steindl TM Palusczak A Hartmann RW Langer T 《Journal of chemical information and modeling》2006,46(3):1301-1311
Cytochrome P450 19 (P450 19, aromatase) constitutes a successful target for the treatment of breast cancer. This study analyzes chemical features common to P450 19 inhibitors to develop ligand-based, selective pharmacophore models for this enzyme. The HipHop and HypoRefine algorithms implemented in the Catalyst software package were employed to create both common feature and quantitative models. The common feature model for P450 19 includes two ring aromatic features in its core and two hydrogen bond acceptors at the ends. The models were used as database search queries to identify active compounds from the NCI database. 相似文献
1000.
Daniela Tardito Marco Milanese Tiziana Bonifacino Laura Musazzi Massimo Grilli Alessandra Mallei Elisabeth Mocaer Cecilia Gabriel-Gracia Giorgio Racagni Maurizio Popoli Giambattista Bonanno 《BMC neuroscience》2010,11(1):1-4