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排序方式: 共有169条查询结果,搜索用时 31 毫秒
91.
Jinkun Huang Emilio Bunel Alan Allgeier Jason Tedrow Thomas Storz J. Preston Tiffany Correll Deana Manley Troy Soukup Randy Jensen Rashid Syed George Moniz Robert Larsen Michael Martinelli Paul J. Reider 《Tetrahedron letters》2005,46(45):7831-7834
Rh(CO)2(acac)/TangPhos was found to be a highly enantioselective catalyst for asymmetric hydroformylation of norbornylene under mild conditions. Application of the protocol to the desymmetrization of other [2.2.1]-bicyclic olefins gave moderate to excellent enantioselectivity (55-92% ee). 相似文献
92.
Blewett AJ Varma D Gilles T Butcher R Jacob J Amazan J Jansen SA 《Journal of AOAC International》2011,94(1):110-117
In recent years, there has been a large increase in the use of pharmaceutical compounding to prepare medications that are not commercially available. The treatment of asthma typically includes the use of albuterol (ALB), ipratropium bromide (IPB), and/or budesonide (BUD) nebulizer solutions. There is currently no commercially available nebulizer solution containing all three of these compounds, and patients must rely on often-unregulated compounding. There is a distinct need for methodologies that can be used to analyze compounded formulations to ensure patient safety. We report an HPLC-UV method to separate and quantitate ALB, IPB, and BUD in nebulizer solutions. The method used a gradient elution to achieve separation via an RP C18 column. The method was validated, showed good selectivity, and was linear over several orders of magnitude. The method was applied to the analysis of nebulizer solutions and determination of their storage stability. Significant ALB-dependent degradation occurred within 5 h in solutions formulated with the free base of ALB, while those containing the sulfate salt of ALB produced no degradation. Alkali solutions can cause base-catalyzed hydrolysis of IPB and degradation of BUD. Compounded formulations containing ALB need to include an acid to control pH and prevent degradation. 相似文献
93.
Porta T Grivet C Knochenmuss R Varesio E Hopfgartner G 《Journal of mass spectrometry : JMS》2011,46(2):144-152
Analysis of low molecular weight compounds (LMWC) in complex matrices by vacuum matrix-assisted laser desorption/ionization (MALDI) often suffers from matrix interferences, which can severely degrade limits of quantitation. It is, therefore, useful to have available a range of suitable matrices, which exhibit complementary regions of interference. Two newly synthesized α-cyanocinnamic acid derivatives are reported here; (E)-2-cyano-3-(naphthalen-2-yl)acrylic acid (NpCCA) and (2E)-3-(anthracen-9-yl)-2-cyanoprop-2enoic acid (AnCCA). Along with the commonly used α-cyano-4-hydroxycinnamic acid (CHCA), and the recently developed 4-chloro-α-cyanocinnamic acid (Cl-CCA) matrices, these constitute a chemically similar series of matrices covering a range of molecular weights, and with correspondingly differing ranges of spectral interference. Their performance was compared by measuring the signal-to-noise ratios (S/N) of 47 analytes, mostly pharmaceuticals, with the different matrices using the selected reaction monitoring (SRM) mode on a triple quadrupole instrument equipped with a vacuum MALDI source. AnCCA, NpCCA and Cl-CCA were found to offer better signal-to-noise ratios in SRM mode than CHCA, but Cl-CCA yielded the best results for 60% of the compounds tested. To better understand the relative performance of this matrix series, the proton affinities (PAs) were measured using the kinetic method. Their relative values were: AnCCA > CHCA > NpCCA > Cl-CCA. This ordering is consistent with the performance data. The synthesis of the new matrices is straightforward and they provide (1) tunability of matrix background interfering ions and (2) enhanced analyte response for certain classes of compounds. 相似文献
94.
Jenkins RM Pinder TA Hatley ML Reibenspies JH Darensbourg MY 《Inorganic chemistry》2011,50(5):1849-1855
The versatile N(2)S(2) tetradentate ligands (bme-daco)(2-), (bme-dach)(2-), and (ema)(4-) are known to accommodate many divalent transition-metal ions (M = Ni(II), Pd(II), Pt(II), Pb(II), Zn(II), Cd(II), Cu(II), and Fe(II)) while maintaining reactivity at the S-thiolate sites of the respective N(2)S(2)M complexes. The vanadyl ion, of interest for its pharmacological possibilities and its spin-label reporter properties for bioinorganic studies, also shows an affinity for such mixed nitrogen/sulfur-donor environments. Thus, (V≡O)(2+) analogues of a well-characterized series of N(2)S(2)Ni complexes have been prepared as mimics of possible N(2)S(2)(V≡O) formed from in vivo binding sites of the tripeptide motif, Cys-X-Cys. The nucleophilicity of the S-thiolate in these systems is explored with alkylating agents. IR [ν(VO)], electronic spectral, and electron paramagnetic resonance measurements are presented. X-ray diffraction studies of (bme-daco)(V≡O), (bme-dach)(V≡O), and [Et(4)N](2)[(ema)(V≡O)] further characterize the vanadyl complexes. A comparison of the spectral properties with the product of vanadyl interaction with the CGC tripeptide, the biological analogue of the tetraanionic N(2)S(2) ligand, is given. 相似文献
95.
Christopher J. Stromberg Casey L. KohnhorstGlenn A. Van Meter Elizabeth A. RakowskiBenjamin C. Caplins Tiffany A. GutowskiJennifer L. Mehalko Edwin J. Heilweil 《Vibrational Spectroscopy》2011,56(2):219-227
Using Raman, terahertz (THz), and mid-infrared (IR) spectroscopies, the vibrational spectra of two chromophore models of hydrogen-producing [FeFe]-hydrogenase, Fe2(μ-S2C3H6)(CO)6 and Fe2(μ-S2C2H4)(CO)6, have been assigned. The combination of absorption and scattering techniques, along with DFT calculations, allows for assignments to be made without traditional isotopic substitution methods. 相似文献
96.
Tiffany Burch 《代数通讯》2013,41(8):3622-3625
A converse to Lie's theorem for Leibniz algebras is found and generalized. The result is used to find cases in which the generalized property, called triangulable, is 2-recognizable; that is, if all 2-generated subalgebras are triangulable, then the algebra is also. Triangulability joins solvability, supersolvability, strong solvability, and nilpotentcy as a 2-recognizable property for classes of Leibniz algebras. 相似文献
97.
98.
99.
Lulevich V Zink T Chen HY Liu FT Liu GY 《Langmuir : the ACS journal of surfaces and colloids》2006,22(19):8151-8155
We report herein the establishment of a single-cell compression method based on force measurements in atomic force microscopy (AFM). The high-resolution bright-field or confocal laser scanning microscopy guides the location of the AFM probe and then monitors the deformation of cell shape, while microsphere-modified AFM probes compress the cell and measure the force. Force and deformation profiles of living cells reveal a cubic relationship at small deformation (<30%), multiple peaks at 30-70% compression, and a rapid increase at over 80% deformation. The initial compression may be described qualitatively and quantitatively using a simple model of a nonpermeable balloon filled with incompressible fluid. Stress peaks reflect cell membrane rupture, followed by the deformation and rupture of intracellular components, beyond which the cell responses become irreversible. The Young's modulus and bending constant of living cell membranes are extracted from the balloon models, with 10-30 MPa and 17-52 kT, respectively. The initial compression of dead and fixed cells is modeled using Hertzian contact theory, assuming that the cell is a homogeneous sphere. Dead cells exhibit a cytoskeleton elasticity of 4-7.5 kPa, while fixation treatment leads to a dramatic increase in the cytoskeletal Young's modulus (150-230 kPa) due to protein cross-linking by imine bonds. These results demonstrate the high sensitivity of the single-cell compression method to the molecular-level structural changes of cells, which suggests a new generic platform for investigating cell mechanics in tissue engineering and cancer research. 相似文献
100.
Shawn E. Wright Stephanie Richardson‐Solorzano Tiffany N. Stewart Christopher D. Miller Kelsey C. Morris Christopher J. A. Daley Timothy B. Clark 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(9):2860-2864
Ambiphilic molecules, which contain a Lewis base and Lewis acid, are of great interest based on their unique ability to activate small molecules. Phosphine boronates are one class of these substrates that have interesting catalytic activity. Direct access to these phosphine boronates is described through the iridium‐catalyzed C?H borylation of phosphines. An unconventional cationic iridium catalyst was identified as optimal for a range of phosphines, providing good yields and selectivity across a diverse class of phosphine boronates (isolated as the borane‐protected phosphine). A complimentary catalyst system (quinoline‐based silane ligand with [(COD)IrOMe]2) was optimal for biphenyl‐based phosphines. Selective polyborylation was also shown providing bis‐ and tris‐borylated phosphines. Deprotection of the phosphine boronate provided free ambiphilic phosphine boronates, which do not have detectable interactions between the phosphorus and boron atoms in solution or the solid state. 相似文献