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91.
A simple high-performance liquid chromatography assay using fluorescence detection for the major metabolite of the gastric prokinetic drug cisapride, norcisapride, is presented. Analysis is performed using an Alltech Platinum EPS C8 column with a mobile phase made up of methanol and 0.02M sodium dihygrogen phosphate (45:55, v/v) containing triethylamine (1 g/L). Complete resolution is achieved among norcisapride, the internal standard (metoclopramide), and endogenous urinary components. The assay is linear over the range 50-2000 ng/mL with a mean recovery of 71.2% across the analytical range following solvent extraction with toluene-isoamyl alcohol (95:5, v/v). Intraday coefficients of variation (precision) determined at 200 and 1000 ng/mL are 6.0 and 9.8%, respectively, and interday coefficients of variation are 8.8 and 6.6%, respectively. Intra- and interassay accuracy (as mean relative error) determined at the same concentrations is within 10% in all cases. An analysis of urine samples from a healthy volunteer following the administration of a single 10-mg oral dose of cisapride is shown. 相似文献
92.
Calcite crystals nucleate on the (01.2) face on a diverse range of organic substrates, including self-assembled monolayers, hydrogen-bonded ribbons, and polymer rafts. The (01.2) face of calcite is a polar surface. Therefore macroscopic crystal growth can only occur if the dipole moment is quenched. We demonstrate that the dipole moment can be quenched for a given polar direction by adsorption onto an organic substrate with arbitrary charge density. The density of ions in the outer calcium plane must be modified, by introducing rows of vacancies, to fulfill the condition of zero net dipole moment. Interfacial energies are calculated for interfaces between the polar (01.2) and (00.1) faces of calcite and stearic acid monolayers with a range of densities. It was found that, contrary to the experimental evidence, the (00.1) face has lower interfacial energy than the (01.2) face with monolayers with equivalent densities. We give an explanation for this discrepancy based on kinetic models. 相似文献
93.
The reaction of manganese pentacarbonyl anion with chloromethylidyne tricobaltnonacarbonyl, (μ3-CCl)Co3(CO)9, leads to reduction of the cluster with formation of Mn2(CO)10 and Co(CO), whilst reaction of Mn(CO) with the bis(diphenylphosphino)methane (dppm)-stabilised cluster (μ3-CCl)Co3(CO)7(μ-dppm) leads to the formation of (μ3-CH)Co2Mn(CO)8(μ-dppm), 1. The unique feature of the structure of 1 is the incorporation of a seven-coordinate manganese atom into the metal triangle. 相似文献
94.
95.
Characterization of the Oxygen Binding Motif in a Ruthenium Water Oxidation Catalyst by Vibrational Spectroscopy
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Erin M. Duffy Dr. Brett M. Marsh Jonathan M. Voss Prof. Etienne Garand 《Angewandte Chemie (International ed. in English)》2016,55(12):4079-4082
For homogeneous mononuclear ruthenium water oxidation catalysts, the Ru–O2 complex plays a crucial role in the rate determining step of the catalytic cycle, but the exact nature of this complex is unclear. Herein, the infrared spectra of the [Ru(tpy)(bpy)(O2)]2+ complex (tpy=2,2′:6′,2′′‐terpyridine; bpy=2,2′‐bipyridine) are presented. The complex [Ru(tpy)(bpy)(O2)]2+, formed by gas‐phase reaction of [Ru(tpy)(bpy)]2+ with molecular O2, was isolated by using mass spectrometry and was directly probed by cryogenic ion IR predissociation spectroscopy. Well‐resolved spectral features enable a clear identification of the O?O stretch using 18O2 substitution. The band frequency and intensity indicate that the O2 moiety binds to the Ru center in a side‐on, bidentate manner. Comparisons with DFT calculations highlight the shortcomings of the B3LYP functional in properly depicting the Ru–O2 interaction. 相似文献
96.
Unsaturated keto-lactams undergo sequential conjugate reduction-aldol cyclization on treatment with SmI 2 to give syn-spirocyclic pyrrolidinones and piperidinones containing vicinal, fully substituted stereocenters with complete diastereocontrol. The substituent on nitrogen and the lactam ring size have a marked impact on the efficiency of the spirocyclization. 相似文献
97.
[reaction: see text] An efficient two-pot, asymmetric synthesis of benzothiadiazine-substituted tetramic acids is reported. Starting from commercially available alpha-amino acids or esters, reductive amination followed by a novel one-pot amide bond formation/Dieckmann cyclization provided the desired products in high yield and optical purity. An analogous solid-phase approach to the same targets is also presented. These compounds were found to be potent inhibitors of hepatitis C virus RNA-dependent RNA polymerase. 相似文献
98.
Duffy L Sikivie P Tanner DB Asztalos S Hagmann C Kinion D Rosenberg LJ van Bibber K Yu D Bradley RF 《Physical review letters》2005,95(9):091304
Theoretical arguments predict that the distribution of cold dark matter in spiral galaxies has peaks in velocity space associated with nonthermalized flows of dark matter particles. We searched for the corresponding peaks in the spectrum of microwave photons from axion to photon conversion in a cavity detector for dark matter axions. We found none and place limits on the density of any local flow of axions as a function of the flow velocity dispersion over the axion mass range 1.98 to 2.17 microeV. 相似文献
99.
Dr. Bartosz Marzec Dr. David C. Green Dr. Mark A. Holden Dr. Alexander S. Coté Dr. Johannes Ihli Saba Khalid Dr. Alexander Kulak Daniel Walker Dr. Chiu Tang Prof. Dorothy M. Duffy Dr. Yi‐Yeoun Kim Prof. Fiona C. Meldrum 《Angewandte Chemie (International ed. in English)》2018,57(28):8623-8628
Biomineralisation processes invariably occur in the presence of multiple organic additives, which act in combination to give exceptional control over structures and properties. However, few synthetic studies have investigated the cooperative effects of soluble additives. This work addresses this challenge and focuses on the combined effects of amino acids and coloured dye molecules. The experiments demonstrate that strongly coloured calcite crystals only form in the presence of Brilliant Blue R (BBR) and four of the seventeen soluble amino acids, as compared with almost colourless crystals using the dye alone. The active amino acids are identified as those which themselves effectively occlude in calcite, suggesting a mechanism where they can act as chaperones for individual molecules or even aggregates of dyes molecules. These results provide new insight into crystal–additive interactions and suggest a novel strategy for generating materials with target properties. 相似文献
100.
Previously optical basicity was always measured using s-p absorption spectra of Tl+, Pb2+ and Bi3+, but since these spectra are in the UV region, media containing oxides of transition metal aons have been excluded from such measurements. The present work shows that for VO2+ the d-d transition 2B2 → 2E red-shifts with increasing optical basicity, and a study in the Na2O---P2O5 glass system allows comparison with results obtained previously with Tl+ and other probe ions. It is shown that under controlled conditions determination of optical basicity with VO2+ is viable, and since the 2B2 → 2E spectral band occurs in the visible / near-IR region, UV transparency of the medium is no longer necessary. The VO2+ probe therefore offers a means of obtaining optical basicities of glasses containing e.g. PbO, or of metallurgica slags containing e.g. Fe2O3 or MnO. 相似文献