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  • 1
    Electronic Resource
    Electronic Resource
    The Role of Acetylation in Benzidine Metabolism and DNA Adduct Formation in Dog and Rat Liver (1995)
    s.l. : American Chemical Society
    Chemical research in toxicology 8 (1995), S. 711-720 
    Details
    ISSN: 1520-5010
    Source: ACS Legacy Archives
    Topics: Medicine
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/tx00047a011
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  • 2
    Electronic Resource
    Electronic Resource
    Thermospray liquid chromatography/mass spectrometry in deuterium oxide (1988)
    s.l. : American Chemical Society
    Analytical chemistry 60 (1988), S. 2314-2317 
    Details
    ISSN: 1520-6882
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/ac00171a034
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  • 3
    Electronic Resource
    Electronic Resource
    Leishmania salvage and remodelling of host sphingolipids in amastigote survival and acidocalcisome biogenesis (2005)
    Oxford, UK : Blackwell Science Ltd
    Molecular microbiology 55 (2005), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: Sphingolipids (SLs) play essential roles in most eukaryotes, but in the trypanosomatid protozoan Leishmania major their functions differ significantly. Previously we showed that null mutants defective in de novo sphingoid base synthesis (spt2–) lacked SLs but grew well and retained lipid rafts while replicating as promastigotes in vitro. However, they experienced catastrophic defects in membrane trafficking on entry into stationary phase, and failed to differentiate to the infective metacyclic form. Here we showed this mutant retained the ability to enter macrophages silently and inhibit activation, although as expected most parasites were destroyed. However, in mouse infections, after a delay rapidly progressive lesions appeared, and purified amastigotes were fully virulent to macrophages and mice. Mass spectrometry of spt2– amastigote lipids revealed the presence of high levels of parasite-specific inositol phosphorylceramides (IPCs) not synthesized by the mammalian hosts. Inhibitor studies showed that salvage occurs at the level of complex SLs, suggesting that parasites carry out ‘headgroup’ remodelling. Additionally, we describe a new defect of the spt2– promastigotes involving ‘empty’ acidocalcisomes (ACs), which may point to the origin of this organelle from the lysosome-related organelle/multivesicular body biogenesis pathway. However, ACs in spt2– amastigotes appeared quantitatively and morphologically normal. Thus salvage of SLs and other molecules by intracellular amastigotes play key roles in AC biogenesis and parasite survival in the host.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2958.2005.04493.x
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  • 4
    Electronic Resource
    Electronic Resource
    PhoP-regulated Salmonella resistance to the antimicrobial peptides magainin 2 and polymyxin B (2004)
    Oxford, UK : Blackwell Science Ltd
    Molecular microbiology 53 (2004), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: In Salmonella enterica, the PhoP–PhoQ two-component system governs resistance to structurally different antimicrobial peptides including the alpha-helical magainin 2, the β-sheet defensins and the cyclic lipopeptide polymyxin B. To identify the PhoP-regulated determinants mediating peptide resistance, we prepared a plasmid library from a phoP mutant, introduced it into a phoP mutant and selected for magainin-resistant clones. One of the clones harboured the PhoP-activated ugtL gene, deletion of which rendered Salmonella susceptible to magainin 2 and polymyxin B, but not defensin HNP-1. We established that ugtL encodes an inner membrane protein that promotes the formation of monophosphorylated lipid A in the lipopolysaccharide. Inactivation of both ugtL and the regulatory gene pmrA, which controls lipid A modifications required for resistance to polymxyin B (but not to magainin 2) and is post-transcriptionally activated by the PhoP–PhoQ system, resulted in a strain that was as susceptible to polymyxin B as a phoP mutant. The most frequently recovered clone harboured the yqjA gene, which we show is PhoP regulated and required for resistance to magainin 2 but not to polymyxin B or defensin HNP-1. Our results indicate that different PhoP-mediated modifications in lipid A are necessary for resistance to different antimicrobial peptides.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2958.2004.04107.x
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  • 5
    Electronic Resource
    Electronic Resource
    Thermospray liquid chromatographic/mass spectrometric studies with inositol phosphates (1990)
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 19 (1990), S. 597-600 
    Details
    ISSN: 1052-9306
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Thermospray mass spectrometry of inositol mono- and polyphosphates, separated by ion-exchange chromatography, was evaluated for its potential as a general method for quantitative analysis of these substances. The only ions of significant abundance that are produced by the thermospray ionization process result from the total loss of phosphate from inositol. Thus inositol mono-, tris- and hexakisphosphate each gave mass spectra consisting solely of [MH]+ and [MNH4]+ of inositol. When the chromatographic eluates are passed through a heated reactor prior to the thermospray source maximal yields of these ions are obtained. The sensitivity of the technique falls short of that needed for a general method for biological applications, because the lower limit of detection is about 100 pmol μl-1. Inositol phosphates peracetylated on C-hydroxyls were also studied, with separation by ion-exchange chromatography. Again, thermospray ionization produces totally dephosphorylated species, with the highest-mass ions retaining all of the acetyl groups, even when using the thermal reactor. Losses of acetate were also observed. Sensitivity with the acetyl derivative was comparable to that with the underivatized inositol phosphates.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bms.1200191004
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  • 6
    Electronic Resource
    Electronic Resource
    Studies on the permethylation/dephosphorylation of inositol polyphosphates: An approach to a more sensitive assay (1990)
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 19 (1990), S. 771-776 
    Details
    ISSN: 1052-9306
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Methods for the permethylation of inositol phosphates (i.e. the formation of the completely substituted C-O-methyl/P-O-methyl derivatives) have been studied as a precursor to preparing C-O-methyl inositols where the remaining inositol hydroxyl groups are at the positions originally occupied by the phosphomonoesters. Classical sodium-driven methylations, diazomethane methylations and methylation with methyl trifluoromethanesulfonate were studied and only the latter was found to produce completely alkylated inositol phosphates. Treatment of the permethylated substrates with methanolic HCl removed the dimethylphosphate groups to produce C-O-methyl inositols which are candidates for negative ion chemical ionization gas chromatographic/mass spectrometric analysis as heptafluorobutyryl C-O-methyl inositols. As an example, gas chromatographic/mass spectrometric analysis of myo-inositol 1,2,6-trisphosphate was carried out by methylation, dephosphorylation and conversion to the tris(heptafluorobutyryl) derivative. Detection at the low-femtomole level was achieved by this means. A limitation of the method may be that the methylation procedure appears to produce a variable degree of phosphate positional isomerization, with resulting loss of specificity. If stable isotope internal standards were available for the inositol polyphosphates of interest, this limitation could be compensated for.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bms.1200191204
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  • 7
    Electronic Resource
    Electronic Resource
    Readily synthesized calibration compounds for quadrupole and magnetic instruments for use over the mass range to 2000 daltons (1991)
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 20 (1991), S. 339-344 
    Details
    ISSN: 1052-9306
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Volatile mass calibration standards have been prepared by esterifying β-cellobiose (4-β-D-glucopyranosyl-D-glucose) with a mixture of heptafluorobutyric (HFB) anhydride and pentafluoropropionic (PFP) anhydride. The mixed esters produce spectra that are useful for mass spectrometer calibration with positive or negative ion methane chemical ionization and electron impact over the mass range 300-2000. The spectra contain prominent ions spaced at m/z 20 and m/z 50 intervals. Using the mixed ester with direct insertion probe introduction gives intense spectra that persist for tens of minutes. All signals above m/z 194 derived from these substances disappear rapidly upon withdrawal of the probe. The composition and exact masses are given for the positive and negative ion spectra of a mixed HFB/PFP ester of β-cellobiose. Two other calibrants are described: one made from β-cellobiose using a mixture of HFB, PFP and trifluoroacetic anhydrides, and another the HFB/PFP mixed ester of perseitol. These are examples of the flexibility of this approach with respect to mass range and ion composition.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bms.1200200602
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  • 8
    Electronic Resource
    Electronic Resource
    Thermospray high performance liquid chromatography/mass spectrometric identification of a bladder carcinogen metabolite isolated from guinea pig urine (1990)
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 19 (1990), S. 601-608 
    Details
    ISSN: 1052-9306
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: An in vivo uninary metabolite of the bladder carcinogen 2-amino-4-(5-nitro-2-furyl) thiazole was isolated from guinea pig urine and was identified by direct analysis using thermospray mass spectrometry/high-performance liquid chromatography as 1-(2-amino-4-(5-nitro-2-furyl)-2-thiazolyl)-1-deoxy-β-D-glucopyranuronic acid. The structure of this metabolite was also established by chemical synthesis. Both positive and negative ion thermospray mass spectrometry of the conjugate showed fragment ions resulting from cleavage across the pyran ring of the glucuronic acid comprising of aglycone moiety. These characteristic fragment ions may be diagnostic for identification of N-glucuronides from O-glucuronides.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bms.1200191005
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  • 9
    Electronic Resource
    Electronic Resource
    Water as a useful calibrant for thermospray mass spectrometry (1992)
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 21 (1992), S. 363-364 
    Details
    ISSN: 1052-9306
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The present report demonstrates that thermospray liquid chromotography/mass spectrometry (LC/MS) calibration can be easily achieved by the observation of water cluster ions in filament-on or discharge ionization modes. Cluster ions of sizes ranging from 1 to 44 water molecules are readily observed and thus are useful over the mass range from 17 to 792 Da.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bms.1200210708
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