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  • 1
    ISSN: 0030-4921
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Rates of rotation about the C-9-C-ar bond of 9-(2-isopropylphenyl) fluorene were measured by 1H DNMR, 13C DNMR, double resonance, and a kinetic method. The kinetic data obtained by these methods were critically examined. The DNMR methods afforded satisfactory results if rate data obtained by total line shape analyses of complicated signals with couplings were used, and those derived from simple patterns were abandoned. Agreement among the data yielded by the four different methods was excellent, provided that the data which might contain dubiously large errors were excluded.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 9 (1982), S. 390-394 
    ISSN: 0306-042X
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Geographic variations in the carbon isotope composition of the human diet and human hair were investigated. The carbon isotopic composition of common foodstufls purchased in Chicago, USA, Tokyo, Japan and Munich, FRG, were determined by combustion and differential isotope ratio mass spectrometry. The dietary protein carbon for the United States (-18.1‰) was calculated to be enriched in 13C relative to the Japanese (-21.2‰) and the German (-23.6‰) diets. To a large degree, the differences reflected the consumption of corn-fed animal products in the United States and Japan, as well as seafood in Japan. The carbon isotopic composition of hair (-16.4, -18.0 and -20.4%) for the three respective populations correlated with the calculated values of the dietary protein, but were 2-3% enriched in 13C. Changes in the isotopic composition of beard hair were shown to record the changes in dietary composition in travelers visiting the respective regions.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 11 (1984), S. 557-561 
    ISSN: 0306-042X
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Natural differences in 13C/12C ratios of various metabolic fuels can produce systematic changes in the 13C/12C ratio of breath CO2, and therefore introduce errors into 13CO2 breath tests. To gain insight into the potential problem, we compared 13C/12C ratios of plasma macronutrients to those of breath CO2 under conditions that should alter the percentages of carbohydrate and lipid being oxidized. In rats, 48 h of starvation decreased the 13C/12C ratio of breath CO2 by 3.5‰. At this time the 13C/12C ratio of breath CO2 was very similar to that of plasma lipids. In humans, 30 min of heavy exercise increased the breath 13CO2/12CO2 ratio by 1.3‰. These changes in breath 13C/12C ratios could be predicted from 13C/12C ratios of plasma macronutrients and the percentage of carbon dioxide derived from each macronutrient, but only when compared within the same populations. For example, the 13C/12C ratios of plasma macronutrients of residents of Chicago, Illinois (USA) and Tokyo (Japan) differed by 1-3‰. An empirical correction of 13CO2 breath test data is recommended when breath tests are run under conditions that will change metabolic fuel utilization.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    X-Ray Spectrometry 4 (1975), S. 117-118 
    ISSN: 0049-8246
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: The chemical shift of V Kβ1, 3 and width of V Kα1 were measured with a two crystal X-Ray spectrometer. It was found that V Kβ1, 3 shift and V Kα1width can be utilized for identification of the vanadium oxidation state. Applications to vanadium containing catalysts and several perovskite structure compounds are discussed.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 8 (1985), S. 154-155 
    ISSN: 0935-6304
    Keywords: High performance ion-exchange chromatography ; Recovery of proteins ; TSKgel DEAE-5PW and SP-5PW ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 5 Tab.
    Type of Medium: Electronic Resource
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  • 6
    ISSN: 1052-9306
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Feasibility for the structural characterization of modified nucleosides in transfer RNA at low microgram levels has been investigated by using continuous-flow frit-fast atom bombardment liquid chromatography/mass spectrometry (frit-FAB LC/MS). Sample of tRNAPhe from brewer's yeast (Saccharomyces cerevisiae) was used as a main model, and enzymatically hydrolysed by nuclease P1 and alkaline phosphatase. The resulting nucleoside mixture was separated by using a microbore reversed-phase LC column (150 mm × 0.5 mm i.d.) with an aqueous ammonium acetate-methanol gradient, and the mass spectra were acquired on both positive and negative ionization modes. The modified nucleosides were characterized by comparison of the relative LC elution times with authentic nucleosides, and further confirmed by the structural information from the frit-FAB mass spectra where both molecular and base ions were in general observed as intense peaks in both ionization modes. Tyically, 0.06-0.2 A260 units (3-10 μg) of isoaccepting tRNA was enough to obtain full-scan mass spectra of modified nucleosides, often occurring at a frequency of one per tRNA molecule using positive ion detection. The LC/MS system was used to screen modified nucleosides in tRNA of the extremely thermophilic microorganism Pyrodictium occultum.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
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  • 7
    ISSN: 1052-9306
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Isotope ratio (IR) mass spectrometry was evaluated for the study of drug metabolism and balance using 13C,15N2- labelled antipyrine (AP) as a test drug. Rats were given 40 mg kg-1 (13C, 15N2)AP intraperitoneally. Breath, urine, faeces and blood were collected. Except for breath, samples were combusted in sealed quartz tubes. The resulting CO2 and N2 were analysed for excess 13C and 15N, relative to pre-dose samples, by IR mass spectrometry. In addition, blood levels of AP and cumulative excretion of urinary AP metabolites were determined by gas chromatography/mass spectrometry/selected ion monitoring (GC/MS/SIM) and high-performance liquid chromatography (HPLC) respectively. Excess 13C and 15N levels in blood were comparable with observed levels of AP, and urinary recoveries of 13C (42%) were in good agreement with those calculated from HPLC data (45%). N-Demethylation, one of the important pathways of AP metabolism, was most rapidly determined by excess 13CO2 excretion in breath (8%). The IR mass spectral analysis complemented gas chromatographic/mass spectrum and HPLC analyses, and was less complex.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
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  • 8
    ISSN: 1052-9306
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Three ionization methods of liquid chromatography/mass spectrometry (LC/MS) [atmospheric pressure chemical ionization (APCI), thermospray (TSP) and electrospray ionization (ESI)], were characterized by investigating the relationships between sensitivities and polarities of compounds. Log P values and mass spectrometry of three hydroxymethylglutaryl-Coenzyme A (HMG-CoA) reductase inhibitors - pravastatin sodium (including its metabolites and related compounds), lovastatin and simvastatin - were measured. Their log P values ranged from -2.49 to 4.40, and in LC/MS each of the ionization methods gave different quasi-molecular ions and sensitivities. The APCI method showed a high sensitivity of several nanograms for hydrophobic compounds (log P 〉 2), but was not effective for hydrophilic compounds, such as glutathione conjugate. The TSP method was found to be applicable to all compounds used in this study, and was more sensitive for hydrophobic compounds. The ESI method was also applicable to all compounds (up to 20 ng), and was 10-100 times more sensitive than the other methods in the case of hydrophilic compounds. These results suggest that hydrophobicity of compounds related to efficiency of LC/MS ionization.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
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  • 9
    ISSN: 1052-9306
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Isomerization and degradation of benzylpenicillin ((2S,5R,6R)-3,3-dimethyl-7-oxo-6-(2-phenylacetamido)-4-thia-1-azabicyclo[3.2.0]heptane-2-carboxylic acid) were studied using a combination of PlasmasprayTM (PSP) liquid chromatography/tandem mass spectrometry (LC/MS/MS) and liquid secondary ion tandem mass spectrometry (LSI MS/MS). Benzylpenicillin was isomerized to benzylpenicillenic acid (3-mercapto-N-[[5-oxo-2-(phenylmethyl)-4(5H)-oxazolylidene] methyl] valine) in the PSP interface/ion source. The isomerization was inferred from the probe temperature dependence of PSP LC tandem mass spectra and discrepancies in the daughter ions between PSP LC and LSI tandem mass spectra. High temperature at the PSP interface was responsible for the isomerization, since the difference between PSP LC and LSI tandem mass spectra became smaller as the probe temperature was lowered. It was also found that benzylpenicillin was decomposed to benzylpenilloic acid (5,5-dimethyl-2-[(phenylacetamido)methyl] thiazolidine-4-carboxylic acid), N-(phenylacetyl)glycine, N-(phenylacetyl)glycinal and 3-mercaptovaline in the PSP interface/ion source. The degradation products formed in the interface/ion source were identical to those formed in acidic solution. The results show that degradation of penicillins can be investigated by PSP LC/MS and PSP LC/MS/MS.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 10 (1987), S. 525-526 
    ISSN: 0935-6304
    Keywords: Ion-exchange chromatography of proteins ; Sample loading capacity ; TSKgel SP-5PW ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
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