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  • 1985-1989  (19)
  • Analytical Chemistry and Spectroscopy  (15)
  • Genetics  (4)
  • 1
    Electronic Resource
    Electronic Resource
    Rapid identification of drug metabolites with tandem mass spectrometry (1988)
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 15 (1988), S. 193-204 
    Details
    ISSN: 0887-6134
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A method which involves the use of tandem mass spectrometry (MS/MS) for the identification of drug metabolites has been demonstrated with a triple quadrupole mass spectrometer. The method is based on the fact that metabolites usually retain various substructures of the original drug molecule. MS/MS is capable of rapidly identifying molecules with characteristic substructures without prior separation. It is shown that this method makes it possible to postulate possible drug metabolite structures rapidly and systematically without the use of standards. The MS/MS method, as it was applied to the identification of the metabolites of a new antiepileptic drug, zonisamide, is discussed. In this case it was possible to identify isomeric metabolites due to their differences in vaporization times off the probe and their different daughter spectra. The complementary uses of the neutral loss and parent scans for the determination of the site of metabolism is demonstrated. A new figure of merit, the limit of identification, is introduced. The amount of the epoxide metabolite of carbamazepine necessary for its reliable identification in urine was shown to be 0.4 ng/μl. The application of various techniques to confirm preliminary findings with this MS/MS method are described.
    Additional Material: 12 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bms.1200150403
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  • 2
    Electronic Resource
    Electronic Resource
    Formation of the bicarbonate anion from deprotonated oxalic acid (1988)
    New York, NY : Wiley-Blackwell
    Rapid Communications in Mass Spectrometry 2 (1988), S. 275-276 
    Details
    ISSN: 0951-4198
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/rcm.1290021207
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  • 3
    Electronic Resource
    Electronic Resource
    Do the benzyl and silabenzyl anions show similar ion chemistry in the gas phase? (1989)
    New York, NY : Wiley-Blackwell
    Rapid Communications in Mass Spectrometry 3 (1989), S. 293-294 
    Details
    ISSN: 0951-4198
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: The ion PhSiH2- undergoes a number of fragmentations upon collisional activation, including losses of H·, H2 (mainly to form PhSi-), and SiH2, together with formation of HSi-. The ion/molecule chemistry of PhSiH2- is characteristic of silyl anion systems and bears no analogy to that of benzyl anion reactions; for example with N2O and CO2 it forms Ph(H)2SiO- as the sole ionic product, while with CS2 it yields Ph(H)2SiS-.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/rcm.1290030905
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  • 4
    Electronic Resource
    Electronic Resource
    Analysis of inositol mono- and polyphosphates by gas chromatography/mass spectrometry and fast atom bombardment (1986)
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 13 (1986), S. 333-341 
    Details
    ISSN: 1052-9306
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The electron ionization spectra of all of the positional isomers of myo-inositol monophosphate and of myo-inositol 1,2-cyclic phosphate were obtained by gas chromatography/mass spectrometry of the pertrimethylsilyl derivatives. The fragmentation pattern of pertrimethylsilyl myo-inositol-1-phosphate was studied using deuterium labeling. The phosphate moiety was found to direct fragmentation to produce fragment ions of useful intensity with specific carbon retention. The spectrum of pertrimethylsilyl myo-inositol-1,4-bisphosphate is also described. An electron impact gas chromatographic/mass spectrometric method for myo-inositol-1-phosphate has been developed, which has a sensitivity to a level of 0.1 pmol. The positive and negative ion fast atom bombardment spectra of myo-inositol hexakis(disodium phosphate) and myo-inositol hexakis(dihydrogen phosphate) are described. The lesser-phosphorylated inositol polyphosphates were also studied, including inositol pentakis and inositol tetrakis(dihydrogen phosphates) as well as D-myo-inositol-1,4,5-trisphosphate and D-myo-inositol-1,4-bisphosphate from human red blood cells. The sensitivity of fast atom bombardment for the measurement of the latter two substances allows their detection to a level of about 10 nmol. The fast atom bombardment spectrum of synthetic myo-inositol 1,2-cyclic phosphate revealed variable amounts of a dimer produced during its preparation.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bms.1200130704
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  • 5
    Electronic Resource
    Electronic Resource
    The oxyisocyanate [ONCO]- and amidoisocyanate [HNNCO]- negative ions (1989)
    New York, NY : Wiley-Blackwell
    Rapid Communications in Mass Spectrometry 3 (1989), S. 151-152 
    Details
    ISSN: 0951-4198
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: Ab initio calculations indicate that the ion [ONCO]- is linear, whereas [HNNCO]- is effectively coplanar. The ions may be formed by collisional activation of deprotonated hydroxy and aminocarbamates. The characteristic fragmentations of [ONCO]- and [HNNOO]- are losses of O and NH respectively.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/rcm.1290030509
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  • 6
    Electronic Resource
    Electronic Resource
    Are penta-coordinate silyl anions the sole intermediates in reactions of nucleophiles with organosilanes? (1989)
    New York, NY : Wiley-Blackwell
    Rapid Communications in Mass Spectrometry 3 (1989), S. 10-11 
    Details
    ISSN: 0951-4198
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/rcm.1290030106
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  • 7
    Electronic Resource
    Electronic Resource
    Post-transcriptional regulation and DNA undermethylation of intracisternal A particle genes in embryonal carcinoma cell lines (1987)
    Chichester [u.a.] : Wiley-Blackwell
    Developmental Genetics 8 (1987), S. 125-133 
    Details
    ISSN: 0192-253X
    Keywords: retrovirus ; embryonal carcinoma ; embryonic gene ; DNA methylation ; gene expression ; Life and Medical Sciences ; Genetics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: Northern blot analysis and in vitro nuclear transcription assays were performed in order to clarify conflicting reports on the expression of intracisternal A particle (IAP) genes in embryonal carcinoma (EC) cell lines. Results demonstrate that post-transcriptional mechanisms control the final steady-state levels of IAP RNA in EC cells. IAP genes were further found to be undermethylated in IAP-expressing EC cell lines.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/dvg.1020080302
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  • 8
    Electronic Resource
    Electronic Resource
    Control of early gene expression in Dictyostelium (1988)
    Chichester [u.a.] : Wiley-Blackwell
    Developmental Genetics 9 (1988), S. 337-350 
    Details
    ISSN: 0192-253X
    Keywords: Dictyostelium ; cAMP ; receptor ; gene regulation ; Life and Medical Sciences ; Genetics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: We have examined the expression of a cAMP pulse-repressed and two cAMP pulse-induced genes in response to cAMP and caffeine under a number of different physiological conditions, and in several classes of developmental mutants altered in cAMP-mediated signal transduction pathways. The data presented help characterize the mutants with regard to early gene expression. Analysis of the data indicates that full induction of the pulse-induced or repression of the pulse-repressed genes requires cycles of activation and adaptation of the cAMP receptor but does not require a rise in intracellular cAMP. Comparison of the results obtained between different mutant classes suggests that repression and activation of the two classes of genes can be uncoupled, implying that different intracellular mechanisms control these processes. In addition, we examined the effects of caffeine and show that it can induce pulse-induced mRNA accumulation in the absence of cAMP.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/dvg.1020090415
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  • 9
    Electronic Resource
    Electronic Resource
    Doubly charged porphyrin ion tandem mass spectrometry: Implications for structure elucidation (1989)
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 24 (1989), S. 875-884 
    Details
    ISSN: 0030-493X
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Under electron ionization (EI) conditions, porphyrins yield unusually high intensities of doubly charged molecular and fragment ions. These doubly charged ions offer unique opportunities for the structure elucidation of porphyrins by tandem mass spectrometry (MS/MS). First, they fragment to a greater extent than the corresponding singly charged ions under both EI/MS and EI/MS/MS conditions. Second, doubly and singly charged porphyrin ions often fragment via different pathways, and can therefore yield different structural information. This paper describes several ways in which analyses of doubly charged porphyrin ions with a triple quadrupole tandem mass spectrometer can be useful in structure elucidation of porphyrins. The effect of the metal atom on the fragmentation of metalloporphyrins in an EI source is demonstrated by correlating the extent of doubly charged fragment ion formation to a stability index. Doubly charged porphyrin ions are shown to yield predominantly doubly charged daughter ions upon collisionally activated dissociation (CAD), and are also shown to fragment to a greater extent than corresponding singly charged porphyrin ions. Advantages and disadvantages of doubly charged porphyrin ion MS/MS for structure elucidation are discussed.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/oms.1210241005
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  • 10
    Electronic Resource
    Electronic Resource
    Unimolecular and collision-induced fragmentation of protonated nitroarenes (1988)
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 23 (1988), S. 327-333 
    Details
    ISSN: 0030-493X
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The unimolecular fragmentation reactions of 28 protonated nitroarenes, occurring on the metastable ion time-scale, are reported. In addition, the collision-induced fragmentation of the same species have been studied at 10 eV and at 50 eV collision energy. When an OH, COOH or NH2 substituent is ortho to the nitro function, the dominant fragmentation involves loss of H2O, for both unimolecular and collision-induced reactions. When there is an electron-releasing substituent ortho or para to the litro group, loss of OH is the dominant fragmentation reaction both on the metastable ion time-scale and for ions activated by collision. When the electron-releasing substituent is meta to the nitro group, loss of NO2 is the dominant low-energy unimolecular fragmentation reaction while loss of HNO2 is the most important fragmentation for ions activated by 50 eV collisions. Elimination of NO from [MH]+ occurs to a significant extent in the unimolecular fragmentation of protonated nitrobenzene and those protenated nitrobenzenes containing electron- attracting substituents. In the collision-induced dissociation of these species loss of HNO2 occurs at the expense of loss of NO. The results are consistent with protonation predominantly at the nitro group. The results are discussed in terms of the use of neutral loss scans in tandem mass spectrometry to monitor complex mixtures for nitroarenes.
    Additional Material: 3 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/oms.1210230507
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