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  • 1
    Digitale Medien
    Digitale Medien
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 4 (1977), S. v 
    ISSN: 1052-9306
    Schlagwort(e): Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 2
    ISSN: 1052-9306
    Schlagwort(e): Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Submicrogram to microgram samples of a variety of proteins have been analyzed using a reaction interface and a mass spectrometer. The interface atomizes the macromolecule in a microwave discharge and produces simple polyatomic molecules from the elements contained in the analyte by reaction with a scavenger gas. The measurement of m/z 64 for SO2 in a CO2-scavenged discharge can be used to determine the amount of sulfur originally introduced into the interface; carbon is quantified as HCN (m/z 27) in a nitrogen-scavenged discharge. Because of the highly energetic, destructive nature of the reaction interface, the character of the original molecule, i.e. size, polarity, etc., does not affect the analysis, only its elemental content. Samples (1 μg) of a series of 12 amino acid polymers ranging in size from mol. wt 470 (des-TYR-MET-enkephalin) to mol. wt 65 400 (bovine serum albumin) and with a sulfur content of 1 S per amino acid (poly-1-methionine) to 2 S per 153 amino acids (myoglobin) were subjected to elemental analyses of sulfur and carbon. The observed S/C ratio was linear with elemental formual calculation, and produced a log-log regression coefficient of 0.80. With poly-1-methionine (mol. wt 30 000) as a model compound, the detection of sulfur was linear for sample sizes between 20 and 10 000 ng. We conclude that the reaction interface is a promising addition to a mass spectrometer for detection of certain elements from small samples of biological macromolecules.
    Zusätzliches Material: 4 Ill.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 3
    ISSN: 1052-9306
    Schlagwort(e): Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: A gas chromatographic mass spectrometric method for the quantitative determination of imipramine and its N-demethylated metabolite desipramine in plasma samples at the nanogram level is reported. The method involves derivatization of the extracted drugs with trifluoroacetylimidazole, a mild derivatizing reagent. Specificity is provided by selected ion recording of the [M + H]+ ions, formed upon chemical ionization with methane as reagent gas. Quantitation is achieved by stable isotope dilution techniques, using deuterium labeled analogs, prepared by acid-catalyzed exchange, as internal standards. Data on patient samples are presented.
    Zusätzliches Material: 4 Ill.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 4
    Digitale Medien
    Digitale Medien
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 8 (1981), S. 301-304 
    ISSN: 1052-9306
    Schlagwort(e): Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: A gas chromatographic mass spectrometric assay for serotonin (5-hydroxytryptamine) has been developed. Serotonin is acylated in homogenized biological media, efficiently extracted into ethyl acetate, and further derivatized with pentafluoropropionic anhydride. Mass spectral characterization of derivatized serotonin using electron and positive or negative chemical ionization indicates that electron ionization mass spectrometry is useful for serotonin assay in most biological fluids and tissues, but that electron capture negative chemical ionization is required for samples containing less than 1-2 ng (cerebrospinal fluid). An assay limit of 10 pg per sample has been established. Examples of applications for the assay of serotonin in human platelets, rat spinal cord, and monkey cerebrospinal fluid are presented.
    Zusätzliches Material: 2 Ill.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 5
    ISSN: 1052-9306
    Schlagwort(e): Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: A sensitive gas chromatographic mass spectrometric assay has been developed to measure plasma 4-hydroxy-3-methoxyphenylethylene glycol and 3,4-dihydroxyphenylethylene glycol. Following addition of deuterated internal standards, the metabolites are propinylated to facilitate extraction with dichloromethane. After evaporation of the solvent, the residue is derivatized with t-butyldimethysilmidazole. The reaction product is washed with water, evaporated to dryness, and reconstituted with hexane for gas chromatography mass spectrometry. The single major fragment ion from each of the derivatized metabolites is monitored, yielding a sensitivity of approximately 3-5 pmol ml-1. Improved precision for the 3,4-dihydroxyphenylethylene glycol assay may be facilitated by synthesis of a more stable internal standard.
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 6
    Digitale Medien
    Digitale Medien
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 13 (1986), S. 85-89 
    ISSN: 1052-9306
    Schlagwort(e): Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: A sensitive gas chromatographic/mass spectrometric assay has been developed to quantify 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) and 1-methyl-4-phenylpyridinium ion (MPP+) in brain tissue. MPTP was derivatized with isobutyl chloroformate and then analyzed using gas chromatography/mass spectrometry. MPP+, a known metabolite of MPTP, was reduced with NaB2H4 to 2H2-MPTP before derivatization. Deuterated isotopomers of MPTP and MPP+ were used as internal standards. The intra-assay coeffients of variation in the determination of 57.3 ng MPTP and 371.8 ng MPP+ in 100 mg of mouse brain tissue were 3.0% and 5.6% (n = 7), respectively. The detection limit corresponds to about 2 ng per sample of authentic MPTP.
    Zusätzliches Material: 1 Ill.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 7
    ISSN: 1052-9306
    Schlagwort(e): Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: This study contains a practical application of variance analysis for the evaluation of precision in selected ion monitoring using stable isotope variants or chemically related compounds as internal standards. Variance analysis is applied to determine the relative contributions of the errors due to long-term and short-term effects of instrument stability. The technique allows the resolution of variance due to sample manipulation from that introduced by the gas chromatography mass spectrometry instrumentation. This provides an objective measure of potential internal standards. Evaluation of the dependency of these erros upon concentration indicates appropriate weighing factors to be applied for regression analysis.
    Zusätzliches Material: 1 Ill.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 8
    ISSN: 1052-9306
    Schlagwort(e): Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: In a number of infectious and inflammatory diseases, stimulation of the immune system can lead to increased accumulation of tryptophan metabolites via induction of kynurenine pathway enzymes in extrahepatic tissues. We developed a liquid chromatographic/mass spectrometric (LC/MS) method suitable for tracing the disposition of 13C isotopomers of L-tryptophan and L-kynurenine in various cultured cell, tissue slice, and whole animal model systems used to investigate tryptophan flux through the kynurenine pathway. The method employs extractive derivatization of the analytes and their 2H internal standards with pentafluorobenzyl bromide in order to enhance the negative ion chemical ionization (NICI) mass spectrometric response. Normal-phase liquid chromatographic separation of derivatized analytes was optimized using a silica column with organic solvents, followed by particle beam transfer and NICI-MS. Standard curves were linear over the range 1-250 ng per sample. Particle beam and mass spectrometric operating parameters were optimized with direct flow injections of 1-(methylamino) anthra-quinone, which is an ideal test compound for the evaluation of LC/NICI-MS. The developed method was used to quantify the conversion of (13C6)L-tryptophan to (13C6)L-kynurenine by human monocytes (THP-1) stimulated with interferon-γ, lung and brain tissue slices obtained from gerbils immune-stimulated with pokeweed mitogen. The effect of whole body immune stimulation on the plasma levels of engogenous L-kynurenine in mice stimulated with interferon-γ was also quantified.
    Zusätzliches Material: 5 Ill.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 9
    Digitale Medien
    Digitale Medien
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 5 (1971), S. 463-471 
    ISSN: 0030-493X
    Schlagwort(e): Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: A small on-line computer system for complete processing of low resolution magnetic deflection mass spectrometric data has been demonstrated. An interpolated mass scale accuracy of 200ppm was achieved for both repetitive (five or ten second cycle times) and single scan modes. Identification of m/e values above 1000 is possible with an accuracy of 500 ppm to m/e 3600. Mass scale assignments are time based and externally calibrated (pfa).
    Zusätzliches Material: 2 Ill.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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