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81.
Mariam Mnatsakanyan David Shock Tiffany A. Goodie Neil W. Barnett R. Andrew Shalliker 《Talanta》2010,82(4):1349-1827
Differences between alkyl, dipole-dipole, hydrogen bonding, and π-π selective surfaces represented by non-resonance and resonance π-stationary phases have been assessed for the separation of ‘Ristretto’ café espresso by employing 2DHPLC techniques with C18 phase selectivity detection. Geometric approach to factor analysis (GAFA) was used to measure the detected peaks (N), spreading angle (β), correlation, practical peak capacity (np) and percentage usage of the separations space, as an assessment of selectivity differences between regional quadrants of the two-dimensional separation plane. Although all tested systems were correlated to some degree to the C18 dimension, regional measurement of separation divergence revealed that performance of specific systems was better for certain sample components. The results illustrate that because of the complexity of the ‘real’ sample obtaining a truly orthogonal two-dimensional system for complex samples of natural origin may be practically impossible. 相似文献
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Zheng S Barlow S Risko C Kinnibrugh TL Khrustalev VN Jones SC Antipin MY Tucker NM Timofeeva TV Coropceanu V Brédas JL Marder SR 《Journal of the American Chemical Society》2006,128(6):1812-1817
We report the first structural data for bis(diarylamine) "bipolarons": we have isolated and crystallographically characterized salts of the dications obtained by two-electron oxidation of E-4,4'-bis[di(p-anisyl)amino]stilbene and E,E-2,5-bis{4-[di(p-anisyl)amino]styryl}-3,4-di(n-butoxy)thiophene, [1](2+) and [2](2+) respectively. ESR, NMR, and magnetometry suggest both species have singlet ground states. X-ray structures, together with (1)H NMR coupling constants for [2](2+), indicate geometries in which the bond lengths are shifted toward a quinoidal pattern relative to that in the neutral species, but not to a fully quinoidal extent. In particular, the bond-length alternations across the vinylene bridging groups approach zero. DFT calculations with closed-shell singlet configurations reproduce the observed structures well. Our results indicate that singlet species for which one might expect quinoidal geometries (with differences of ca. 0.1 A between formally single and double bonds) on the basis of a limiting valence-bond representation of the structure can, in fact, show structures with significantly different patterns of bond lengths. 相似文献
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Kottani R Majjigapu JR Kurchan A Majjigapu K Gustafson TP Kutateladze AG 《Journal of the American Chemical Society》2006,128(46):14794-14795
Addition of lithiated dithianes to diaryl ketones, potential electron-transfer sensitizers, disrupts conjugation between the two aromatic moieties, effectively masking the sensitizer. A novel photoamplification strategy is developed based on photosensitized cleavage in such adducts, where each fragmentation event releases more diaryl ketone, capable of sensitization. As a result, mass release of dithianes, triggered with a very small amount of the initiator, is observed. Such amplified release can be made contingent on a molecular recognition event, offering a promising methodology for high throughput bioanalytical applications. The concept is proved with the use of micro- and nanosized polymeric supports, including dendrimers. 相似文献
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Kamila Chughtai Lu Jiang Harm Post Paul T. Winnard Jr. Tiffany R. Greenwood Venu Raman Zaver M. Bhujwalla Ron M. A. Heeren Kristine Glunde 《Journal of the American Society for Mass Spectrometry》2013,24(5):711-717
Mass spectrometric imaging (MSI) in combination with electrospray mass spectrometry (ESI-MS) is a powerful technique for visualization and identification of a variety of different biomolecules directly from thin tissue sections. As commonly used tools for molecular reporting, fluorescent proteins are molecular reporter tools that have enabled the elucidation of a multitude of biological pathways and processes. To combine these two approaches, we have performed targeted MS analysis and MALDI-MSI visualization of a tandem dimer (td)Tomato red fluorescent protein, which was expressed exclusively in the hypoxic regions of a breast tumor xenograft model. For the first time, a fluorescent protein has been visualized by both optical microscopy and MALDI-MSI. Visualization of tdTomato by MALDI-MSI directly from breast tumor tissue sections will allow us to simultaneously detect and subsequently identify novel molecules present in hypoxic regions of the tumor. MS and MALDI-MSI of fluorescent proteins, as exemplified in our study, is useful for studies in which the advantages of MS and MSI will benefit from the combination with molecular approaches that use fluorescent proteins as reporters. Figure
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Tatiana Trejos Robert Koons Stefan Becker Ted Berman JoAnn Buscaglia Marc Duecking Tiffany Eckert-Lumsdon Troy Ernst Christopher Hanlon Alex Heydon Kim Mooney Randall Nelson Kristine Olsson Christopher Palenik Edward Chip Pollock David Rudell Scott Ryland Anamary Tarifa Melissa Valadez Peter Weis Jose Almirall 《Analytical and bioanalytical chemistry》2013,405(16):5393-5409
Elemental analysis of glass was conducted by 16 forensic science laboratories, providing a direct comparison between three analytical methods [micro-x-ray fluorescence spectroscopy (μ-XRF), solution analysis using inductively coupled plasma mass spectrometry (ICP-MS), and laser ablation inductively coupled plasma mass spectrometry]. Interlaboratory studies using glass standard reference materials and other glass samples were designed to (a) evaluate the analytical performance between different laboratories using the same method, (b) evaluate the analytical performance of the different methods, (c) evaluate the capabilities of the methods to correctly associate glass that originated from the same source and to correctly discriminate glass samples that do not share the same source, and (d) standardize the methods of analysis and interpretation of results. Reference materials NIST 612, NIST 1831, FGS 1, and FGS 2 were employed to cross-validate these sensitive techniques and to optimize and standardize the analytical protocols. The resulting figures of merit for the ICP-MS methods include repeatability better than 5 % RSD, reproducibility between laboratories better than 10 % RSD, bias better than 10 %, and limits of detection between 0.03 and 9 μg g?1 for the majority of the elements monitored. The figures of merit for the μ-XRF methods include repeatability better than 11 % RSD, reproducibility between laboratories after normalization of the data better than 16 % RSD, and limits of detection between 5.8 and 7,400 μg g?1. The results from this study also compare the analytical performance of different forensic science laboratories conducting elemental analysis of glass evidence fragments using the three analytical methods. Figure
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Bhupinder Sandhu Sergiu Draguta Tiffany L. Kinnibrugh Victor N. Khrustalev Tatiana V. Timofeeva 《Acta Crystallographica. Section C, Structural Chemistry》2013,69(4):421-427
The target complexes, bis{(E,E)‐3,5‐bis[4‐(diethylamino)benzylidene]‐4‐oxopiperidinium} butanedioate, 2C27H36N3O+·C4H4O42−, (II), and bis{(E,E)‐3,5‐bis[4‐(diethylamino)benzylidene]‐4‐oxopiperidinium} decanedioate, 2C27H36N3O+·C10H16O42−, (III), were obtained by solvent‐mediated crystallization of the active pharmaceutical ingredient (API) (E,E)‐3,5‐bis[4‐(diethylamino)benzylidene]‐4‐piperidone and pharmaceutically acceptable dicarboxylic (succinic and sebacic) acids from ethanol solution. They have been characterized by melting point, IR spectroscopy and single‐crystal X‐ray diffraction. For the sake of comparison, the structure of the starting API, (E,E)‐3,5‐bis[4‐(diethylamino)benzylidene]‐4‐piperidone methanol monosolvate, C27H35N3O·CH4O, (I), has also been studied. Compounds (II) and (III) represent salts containing H‐shaped centrosymmetric hydrogen‐bonded synthons, which are built from two parallel piperidinium cations and a bridging dicarboxylate dianion. In both (II) and (III), the dicarboxylate dianion resides on an inversion centre. The two cations and dianion within the H‐shaped synthon are linked by two strong intermolecular N+—H...−OOC hydrogen bonds. The crystal structure of (II) includes two crystallographically independent formula units, A and B. The cation geometries of units A and B are different. The main N—C6H4—C=C—C(=O)—C=C—C6H4—N backbone of cation A has a C‐shaped conformation, while that of cation B adopts an S‐shaped conformation. The same main backbone of the cation in (III) is practically planar. In the crystal structures of both (II) and (III), intermolecular N+—H...O=C hydrogen bonds between different H‐shaped synthons further consolidate the crystal packing, forming columns in the [100] and [10] directions, respectively. Salts (II) and (III) possess increased aqueous solubility compared with the original API and thus enhance the bioavailability of the API. 相似文献
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Justin S. Marcum Tiffany R. Taylor Simon J. Meek 《Angewandte Chemie (International ed. in English)》2020,59(33):14070-14075
A catalytic method for the site‐selective and enantioselective synthesis of functionalized arenes by the intermolecular hydroarylation of terminal and internal 1,3‐dienes with aryl pinacolato boronates is reported. The reactions are promoted by 5.0 mol % of a readily available monodentate phosphoramidite‐Ni complex in ethanol, affording a variety of enantioenriched products in up to 96 % yield and 99:1 er. Mechanistic studies indicate that Ni–allyl formation is irreversible and related to the nature of the arylboronate. 相似文献
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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