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  • Analytical Chemistry and Spectroscopy  (8)
  • Animals  (5)
  • 1995-1999  (2)
  • 1985-1989  (11)
  • 1
    Electronic Resource
    Electronic Resource
    Determination of polycyclic aromatic hydrocarbons in coal fly ash using gas chromatography/negative ion chemical ionization mass spectrometry (1986)
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 13 (1986), S. 95-104 
    Details
    ISSN: 1052-9306
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: This study reports studies using electron capture negative ion chemical ionization gas chromatography/mass spectrometry (EC-NICI GC/MS) of 21 polycyclic aromatic hydrocaroon (PAH) compounds. The selectivity and sensitivity of these compounds are shown here to be highly dependent on ion source temperature and pressure. Changes in selectivity arise from variations in instrumental and can be largely explained by the competitive formation processes of [M]-. and [M—H]- ions. The formation of the adduct ion, [M + 15]-, previously attributed to [M + CH3]-, is shown here by using perdeuterated PAH analogues to be a [M + O — H]- ion. For fluorene and acenaphthene, abundant [M + 14]- and [M + 13]- ions can be similarly rationalized to be [M + O — 2H]- and [M + O — 3H]-. The NICI mass spectrum of (2H10)acenaphthene demonstrates that ring proton losses most likely occur. This study also indicates that there is a strong correlation between the NICI response factor and the reported carcinogenic activity of PAHs in the literature. In addition, this work assesses the viability of NICI GC/MS as an analytical technique for determining PAHs in fly ash with minimum sample pretreatment.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bms.1200130209
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  • 2
    Electronic Resource
    Electronic Resource
    Gas chromatographic/mass spectrometric determination of carbon isotope composition in unpurified samples: Methamphetamine example (1986)
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 13 (1986), S. 531-534 
    Details
    ISSN: 1052-9306
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A gas chromatograph/quadrupole mass spectrometer system, operated in electron impact/selected ion monitoring mode, is used to determine the intensity ratio of the m/z 59 and the m/z 58 ions of the [C3H8N]+ fragment derived from methamphetamine samples synthesized with varying amounts of 13C-labeled methylamine. Crude products are introduced into the gas chromatograph without prior cleanup. The ratios measured were in excellent agreement with those calculated. A change in 0.25% use of 13C-methylamine is sufficient for product differentiation. The feasibility of using isotope labeling and subsequent mass spectrometric isotope ratio measurement as the basis of a compound tracing mechanism is discussed. Specifically, if methamphetamine samples manufactured from legal sources are asked to incorporate distinct 13C compositions, their sources can be traced when samples are diverted into illegal channels. Samples derived from illicit preparations can also be traced if the manufacturers of a precursor (methylamine in this case) incorporate distinct 13C compositions in their products.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bms.1200131003
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  • 3
    Electronic Resource
    Electronic Resource
    Analysis of the constituents of Piper methysticum by gas chromatography methane chemical ionization mass spectrometry. New constituents of kava resin (1986)
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 13 (1986), S. 305-313 
    Details
    ISSN: 1052-9306
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Methane chemical ionization mass spectrometry has been used to investigate the components of kava resin prepared by solvent extraction of commercial Piper methysticum Forst. All the known constitutents of this resin were identified together with several new compounds which of formally result from decarboxylation of the 4-methoxy-2-pyrone ring system in the known compounds. Chemical ionization mass spectrometry is a useful probe for the identification of these compounds because all gave easily recognized protonated molecular ions and the fragmentation patterns were related to molecular structure. Using this technique, the steam distillation products of commercial P. methysticum were identified, as was the product distribution from base hydrolysis of the known kava pyrone, yangonin.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bms.1200130608
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  • 4
    Electronic Resource
    Electronic Resource
    Selected ion monitoring mass spectrometry: Parameters affecting quantitative determination (1985)
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 12 (1985), S. 633-637 
    Details
    ISSN: 1052-9306
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Instrumental parameters and possible correction procedures for hydrogen-transfer phenomena are studied, with emphasis on the improvement of quantitative measurements in selected ion monitoring mass spectrometry. The intensity ratio of the m/z 387 and 386 ions, derived from cholesterol, are measured by an HP-5995 mass spectrometer using different parameters, including calibration peak width, mass filter window size and ion monitoring dwell time. The intrinsic ratio of these two ions is calculated with a correction procedure accounting for the [M—H]+ and [M—2H]+ hydrogen-transfer phenomena.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bms.1200121102
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  • 5
    Electronic Resource
    Electronic Resource
    Negative ion chemical ionization mass spectra of α-amino acid oxazolidinone derivatives (1985)
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 12 (1985), S. 348-354 
    Details
    ISSN: 1052-9306
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Amino acid methyl esters were condensed with 1,3-dichloro-1,1,3,3-tetrafluoroacetone to yield the corresponding oxazolidinone derivatives whose electron capture negative ion methane chemical ionization mass spectra were studied. Anions corresponding to [M + CI]-, (HCI2)- and (CF2CI)2CO)- are discussed in relation to their appearance in the amino acid oxazolidinone spectra. Other common fragmentation modes were the elimination of stable neutral molecules (HCI, HF, CO2) in various combinations from the molecular anion. Aliphatic amino acids having a γ-hydrogen atom relative to the oxazolidinone ring carbonyl group gave an anionic fragment formally equivalent to the McLafferty rearrangement product of positive ion electron impact mass spectrometry.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bms.1200120707
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  • 6
    Electronic Resource
    Electronic Resource
    Direct mass spectrometric determination of 13C enrichment of organic compounds (1985)
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 12 (1985), S. 638-642 
    Details
    ISSN: 1052-9306
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A direct mass spectrometric measurement method is developed for the determination of 13C enrichment and chemical purity of a labelled compound. The labelled compound is mixed with various amounts of unlabelled analogue to provide a series of mixtures containing different but comparable quantities of labelled and unlabelled species. Intensity ratios of selected isotopically anologous ions from these two species are determined using selected ion monitoring. Equations are established to relate measured intensity ratios to sample mixture weight ratios, chemical purities of the labelled and unlabelled compounds, ion composition and isotopic abundance of the enriched and unenriched carbons, A non-linear regression procedure, based on the measured intensity ratio, the mixture weight ratio and the known chemical purity of the unlabelled compound, is used to resolve the chemical purity and the isotopic abundance yielding results with standard errors of 1.0 and 0.4%, respectively. This procedure is suitable for compounds labelled with more than 60% of an isotope.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bms.1200121103
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  • 7
    Electronic Resource
    Electronic Resource
    Further studies on a site-specific hydrogen transfer observed in electron capture negative ion chemical ionization mass spectrometry of hydroxyamine pentafluoropropionate derivatives (1985)
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 20 (1985), S. 595-599 
    Details
    ISSN: 0030-493X
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Further studies have demonstrated that the site-specific hydrogen transfer process involved in the formation of the m/z 145 anion of β-hydroxyamine pentafluoropropionate (PFP) derivatives observed under electron capture negative ion chemical ionization conditions occurs when the two functional groups are separated by up to five carbon atoms. Deuterium labelling has established that the site specificity, transfer of a hydrogen atom from the carbon adjacent to nitrogen to the OPFP group, is maintained in 4-amino-butan-1-ol-N, O-(PFP)2. The corresponding PFP derivatives of the N-methylaminoalkanol-(PFP)2 derivatives lack the m/z 145 species with m/z 163, [OPFP]- being the base anion. Substitution of alkyl groups on the carbon adjacent to oxygen results in a diminution of the ion intensity at m/z 145. with a marked increase in the intensity of m/z 144. The formation of the m/z 145 and 144 anions to proposed to proceed through the intervention of a fluoride ion-molecule complex as outlined in Scheme 1 with the product ion distribution dependent on which of the two pathways is preferred.
    Additional Material: 4 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/oms.1210201002
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  • 8
    Electronic Resource
    Electronic Resource
    Chemical ionization mass spectrometric characteristics of morphine alkaloids (1985)
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 20 (1985), S. 511-514 
    Details
    ISSN: 0030-493X
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The ion-molecular reaction behavior of ten morphine alkaloids with several commonly used reagent gases are studied under chemical ionization mass spectrometry conditions. These studies emphasize the correlation of the structural characteristics of the 10 alkaloids with the following four mass spectrometric parameters: (i) mass shifts of the protonated ion as a result of replacing ammonia with deuterated ammonia as the reagent gas, (ii) relative tendencies of the adduct ion and the protonated ion to lose molecules of water, (iii) relative intensity ratio of the adduct ion and the protonated ion and (iv) tendency of a compound to undergo a reduction reaction.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/oms.1210200806
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  • 9
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    An essential role for DNA adenine methylation in bacterial virulence (1999)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 1999-05-13
    Description: Salmonella typhimurium lacking DNA adenine methylase (Dam) were fully proficient in colonization of mucosal sites but showed severe defects in colonization of deeper tissue sites. These Dam- mutants were totally avirulent and were effective as live vaccines against murine typhoid fever. Dam regulated the expression of at least 20 genes known to be induced during infection; a subset of these genes are among those activated by the PhoP global virulence regulator. PhoP, in turn, affected Dam methylation at specific genomic sites, as evidenced by alterations in DNA methylation patterns. Dam inhibitors are likely to have broad antimicrobial action, and Dam- derivatives of these pathogens may serve as live attenuated vaccines.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Heithoff, D M -- Sinsheimer, R L -- Low, D A -- Mahan, M J -- AI23348/AI/NIAID NIH HHS/ -- AI36373/AI/NIAID NIH HHS/ -- New York, N.Y. -- Science. 1999 May 7;284(5416):967-70.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Molecular, Cellular, and Developmental Biology, University of California, Santa Barbara, CA 93106, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/10320378" target="_blank"〉PubMed〈/a〉
    Keywords: Adenine/metabolism ; Animals ; Bacterial Proteins/metabolism ; *Bacterial Vaccines ; *DNA Methylation ; DNA, Bacterial/metabolism ; Gene Expression Regulation, Bacterial ; Genes, Bacterial ; Lethal Dose 50 ; Methylation ; Mice ; Mice, Inbred BALB C ; Mutation ; Peyer's Patches/microbiology ; Salmonella Infections, Animal/immunology/*microbiology/prevention & control ; Salmonella typhimurium/*enzymology/genetics/immunology/*pathogenicity ; Site-Specific DNA-Methyltransferase (Adenine-Specific)/antagonists & ; inhibitors/genetics/*metabolism ; Vaccines, Attenuated ; Virulence/genetics
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
    Published by American Association for the Advancement of Science (AAAS)
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  • 10
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    Restricted lateral diffusion of PH-20, a PI-anchored sperm membrane protein (1988)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 1988-06-24
    Description: The rate of lateral diffusion of integral membrane proteins is constrained in cells, but the constraining factors for most membrane proteins have not been defined. PH-20, a sperm surface protein involved in sperm-egg adhesion, was shown to be anchored in the plasma membrane by attachment to the lipid phosphatidylinositol and to have a diffusion rate that is highly restricted on testicular sperm, being more than a thousand times slower than lipid diffusion. These results support the hypothesis that lateral mobility of a membrane protein can be regulated exclusively by interactions of its ectodomain.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Phelps, B M -- Primakoff, P -- Koppel, D E -- Low, M G -- Myles, D G -- GM-23585/GM/NIGMS NIH HHS/ -- HD-16580/HD/NICHD NIH HHS/ -- New York, N.Y. -- Science. 1988 Jun 24;240(4860):1780-2.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Physiology, University of Connecticut Health Center, Farmington 06032.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/3381102" target="_blank"〉PubMed〈/a〉
    Keywords: Animals ; Antigens, Surface ; Cell Adhesion Molecules ; Cell Compartmentation ; Cell Membrane/physiology ; Diffusion ; Guinea Pigs ; Male ; *Membrane Fluidity ; Membrane Proteins/*physiology ; Phosphatidylinositols/*physiology ; Sperm Maturation ; Spermatozoa/*physiology ; Testis/physiology
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
    Published by American Association for the Advancement of Science (AAAS)
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