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  • Analytical Chemistry and Spectroscopy  (51)
  • Life and Medical Sciences
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  • 11
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Rapid Communications in Mass Spectrometry 9 (1995), S. 509-511 
    ISSN: 0951-4198
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: The reduction phenomenon of polar compounds that has already been described in fast-atom bombardment (FAB) mass spectrometry also occurs in frit-FAB mass spectrometry.
    Additional Material: 2 Ill.
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  • 12
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Rapid Communications in Mass Spectrometry 3 (1989), S. 127-129 
    ISSN: 0951-4198
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: We describe the kinetics-based measurement protocol which was used for the National Institute of Standards and Technology/Environmental Protection Agency International Round Robin, and provide an interim summary report of the results. At least 50% of the QQQ instruments currently in the field potentially can provide a dynamically correct (i.e., instrument-independent) representation of ion/molecule reactions.
    Additional Material: 1 Tab.
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  • 13
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Rapid Communications in Mass Spectrometry 3 (1989), S. 377-380 
    ISSN: 0951-4198
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: Dynamically correct (i.e., instrument-independent) branching ratios can be measured under single-collision conditions in tandem mass spectrometers incorporating RF-only quadrupole collision cells. The absolute branching ratios were measured as a function of the center-of-mass interaction energy ECM for the collisionally activated dissociation (CAD) of CH3CO+ (m/z43) from several source compounds (ethanol, oxirane), and CH3CO-X (where X = H, CH3, CH3CH2, CH3CO, CH3COCH2, and C6H5)). The energy dependences of the branching ratios for C2H3O+ from CH3CO-X source compounds are quite distinct from those observed for C2H3O+ from ethanol or ethylene oxide, or for the C3H+7 ions (also m/z 43) from n-pentane. Hence, one can use the CAD of m/z 43 to distinguish CH3CO-X compounds from other source compounds, including sources of C3H7+ ions. Therefore, the characteristic branching ratios of ionic substructures may provide for tandem mass spectrometry a „fingerprinting“ capability analogous to the use of group frequencies in infrared spectroscopy.
    Additional Material: 2 Tab.
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  • 14
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Rapid Communications in Mass Spectrometry 3 (1989), S. 427-431 
    ISSN: 0951-4198
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: The collisionally actived dissociation (CAD) of the acetone cation (m/z 58) and of the acetyl cation (m/z 43) from acetone were studied under single-collision and multiple-collision conditions. A kinetics-based measurement protocol developed at the National Institute of Standards and Technology was used to measure the CAD spectra (i.e., the product distributions (branching ratios) of the CAD fragment ions). A protocol is proposed for a second interlaboratory round robin to explore the feasibility (or lack thereof) of measuring standardized, instrument-independent CAD spectra under multiple-collision conditions.
    Additional Material: 2 Tab.
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  • 15
    ISSN: 0951-4198
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: The collisionally activated dissociation (CAD) of the acetone cation (m/z 58) can be used for quality assurance, performance evaluation, and proficiency testing of CAD measurements in tandem mass specstrometry (MS/MS) instruments which use RF-only multipole collision cells. The absolute branching ratios (product distributions) of the CAD fragment ions, when measured as a function of the center-of-mass collision energy Ecm, can provide an objective basis for quality assurance whenever MS/MS methods are used (viz, to validate how well the target thickness, ion-containment efficiency, and collision energy are being controlled in various instruments).
    Additional Material: 1 Tab.
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  • 16
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Cellular Physiology 159 (1994), S. 457-467 
    ISSN: 0021-9541
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Responses of rat submandibular acini to intracellular alkalinization were investigated. Intracellular alkalinization was induced by addition of NH4Cl or methylamines, or by prepulse with Na butyrate. Only partial recovery occurred following Na butyrate prepulse or methylated amine addition, but full recovery was observed following addition of NH4Cl. The latter recovery was DIDS and dimethylamiloride-insensitive but was inhibited by bumetanide or high [K+] and stimulated in Na+ free buffer and by ouabain. Acetylcholine stimulated recovery from NH4Cl- or Na butyrate pre-pulse-induced alkalinization and reduced the extent of alkalinization induced by methylated amines. Acetylcholine-stimulated recovery from NH4Cl-induced alkalinization was mimicked by substance P or ionomycin and was partially Ca2+-dependent. This stimulated recovery was bumetanide-insensitive but was partially sensitive to charybdotoxin. Taken together, these data indicate that in unstimulated cells, recovery from alkalinization induced by NH4Cl occurs by bumetanide-sensitive transport of the NH4+ ion, that DIDS-inhibitable anion transport contributes little to this recovery, and that acetylcholine and other Ca2+-elevating agents accelerate recovery from NH4Cl-induced alkaline challenge by a mechanism insensitive to bumetanide, DIDS, ouabain, and dimethylamiloride but sensitive to extracellular Ca2+ and to charybdotoxin. Partial recovery from alkaline challenge can also occur in the absence of NH4+ ions, and acetylcholine also stimulates this mode of recovery. Together, these data suggest that these cells have little intrinsic ability to recover from intracellular alkalinization and that the NH4+ ion may be a surrogate for K+ in at least two ion transport pathways. © 1994 wiley-Liss, Inc.
    Additional Material: 7 Ill.
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  • 17
    Electronic Resource
    Electronic Resource
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 11 (1984), S. 142-144 
    ISSN: 0306-042X
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The development of an analytical method for the determination of brain tryptamine using capillary gas chromatography mass spectrometry (selected ion monitoring) is presented. The method involves solvent extraction of brain homogenates and further derivatization (pentafluoropropionyl derivatives) of the dried extracts. Gas chrmatographic analysis is performed using a bonded phase silica fused capillary column. Selected monitoring of M/z 289 and 292 (isotope dilution technique) allows the determination of tryptamine in adult rat brain (450 ± 73 pg g-1) (X ± SEM), n = 6.
    Additional Material: 1 Ill.
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  • 18
    ISSN: 0192-253X
    Keywords: Run-on transcription ; developmentally regulated gene expression ; follicle cell nuclei ; Life and Medical Sciences ; Genetics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: To determine the relative roles of transcriptional and post-transcriptional events in establishing the temporal pattern of chorion gene expression in Drosophila, we have examined chorion gene transcription, RNA accumulation, and protein synthesis in follicles of selected pre-early- and late-choriogenic stages. Chorion gene transcription was assayed in follicle cell nuclei by nuclear run-on reactions. For the s 15, s 16, s 18, s36, and s38 chorion genes, the periods of intense transcription are as predicted from the dynamics of RNA accumulation and protein synthesis, indicating that these genes are primarily regulated at the transcriptional level. In contrast, gene s19 appears subject to post-transcriptional control at stage 14, when transcription rates are substantially higher than predicted from the observed RNA levels.Transcription of regions between the clustered and tandemly oriented chorion genes was also examined. In contrast to many RNA polymerase II transcribed genes, for the s18 and s36 chorion genes run-on transcription appears to terminate within about 100 base pairs downstream of the polyadenylation sites, corroborating previous reports based on electron microscopy of s36 [Osheim et al., EMBO J 5:3591-3596, 1986].
    Additional Material: 4 Ill.
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  • 19
    ISSN: 0049-8246
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: A method for correcting the intensity of x-ray fluorescence (limit dilution method) is proposed for the analysis of samples with a complex matrix such as ceramic materials of archaeological interest. This method corrects the interelement effects, resolving the wide deviations which occur in the quantitative results obtained by x-ray fluorescence without correction. The contents of sodium, magnesium, aluminium, silicon, potassium, calcium, titanium and iron in sixteen archaeological ceramic samples of different origins and from different locations were determined. The results obtained are comparable to the values obtained by chemical analysis. A statistical study of the data was carried out to classify the samples hierarchically by cluster analysis of their chemical composition and loss on ignition.
    Additional Material: 3 Ill.
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  • 20
    ISSN: 0049-8246
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: Quantitative methods in x-ray fluorescence analysis require a knowledge of the spectral distribution of the fluorescence-exciting beam. The use of XRF yield measurements of a set of thick pure element targets is proposed for the description of a fluorescence-exciting x-ray beam, without the need to obtain its spectral distribution. This new approach is derived theoretically and verified by comparing thin-target yields calculated from XRF yield measurements of thick pure element specimens with those obtained from a calculated spectral distribution. The difference between the two methods of obtaining the thin-target yields is within 9% relative error.
    Additional Material: 2 Ill.
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