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  • Analytical Chemistry and Spectroscopy  (21)
  • mass spectrometry  (6)
  • 1
    Electronic Resource
    Electronic Resource
    Gradient High Performance Liquid Chromatographic Assay for Degradation Products of Adinazolam Mesylate in a Sustained Release Tablet Formulation (1995)
    Springer
    Pharmaceutical research 12 (1995), S. 738-745 
    Details
    ISSN: 1573-904X
    Keywords: adinazolam mesylate ; gradient reversed-phase liquid chromatography ; mass spectrometry ; decomposition products assay
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract A gradient high performance liquid chromatographic method was developed to determine degradation products of adinazolam mesylate in a sustained release tablet formulation. Sample preparations were chromatographed on a YMC-Basic column using a formate buffer/acetonitrile gradient with absorbance detection at 254 nm. Adinazolam mesylate was found to degrade at high relative humidity and temperature to form a major product, the 6-aminoquinoline analog, plus numerous other compounds. Five of these compounds were identified and their structures indicate that the solid-state degradation of adinazolam, in the presence of sufficient moisture, involves not only a hydrolytic mechanism, but also an oxidative mechanism. Potential process impurities were resolved from the drug and degradation products. Recovery was near 100% over the 0.5 to 10% range for the major degradate (6-aminoquinoline) and over the 0.5 to 1% range for the other analytes. The method was applied to tablet samples stressed at high relative humidity and temperature. The relative standard deviation of the assay for the 6-aminoquinoline was less than 2% and less than 13% for the minor components. Calculated mass balances (sum of adinazolam plus degradation products in the degraded tablet divided by the same sum in the undegraded tablet) were less than 100% and were dependent on the extent of degradation in the tablet. The average mass balance result obtained for samples that were an average of 9.5% degraded was 95.0 ± 1.5%. It is possible that the decrease in mass balance with increase in percent degradation may be explained by the formation of many components at trace levels due to degradation by various permutations of hydrolytic and oxidative reaction pathways.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1016219927912
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  • 2
    Electronic Resource
    Electronic Resource
    Evidence for the Lack of a Human Metabolic Isotope Effect of a Deuterium Analog of Fluphenazine (1995)
    Springer
    Pharmaceutical research 12 (1995), S. 1388-1390 
    Details
    ISSN: 1573-904X
    Keywords: fluphenazine ; stable isotope ; deuterium labeled ; mass spectrometry ; schizophrenics ; pharmacokinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1016298329188
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  • 3
    Electronic Resource
    Electronic Resource
    Structural analysis of bovine pancreatic thread protein (1990)
    Springer
    The protein journal 9 (1990), S. 623-632 
    Details
    ISSN: 1573-4943
    Keywords: Pancreatic thread protein ; primary structure ; mass spectrometry
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Pancreatic thread protein (PTP) forms double helical threads in the neutralpH range after purification, undergoing freely reversible,pH-dependent globule-fibril transformation. The purified bovine PTP consists on SDS gels of two carbohydrate-free polypeptide chains (Grosset al., 1985). Plasma desorption mass spectrometry and amino acid sequence analysis now confirm that bovine PTP contains two disulfide-bonded polypeptides, an A chain of 101 amino acid residues with a molecular weight of 11,073 and a B chain of 35 residues with a molecular weight of 3970. The intact protein exhibits a molecular weight of 15,036, agreeing 〉99.9% with the molecular weight calculated from the sequence. The B chain sequence was determined by gas-phase Edman degradation of the intact polypeptide. The A chain sequence was determined from overlapping peptides generated by cleavage at lysyl, tryptophanyl, and aspartyl-prolyl residues. Based upon the bovine PTP cDNA structure, the two chains of the protein result from cleavage of a single polypeptide with removal of a dipeptide between the NH2-terminal A chain and COOH-terminal B chain. Comparison of bovine PTP with other proteins reveals significant structural relatedness with the single-chain homologues from human and rat pancreas and with the motif associated with Ca2+-dependent carbohydrate recognition domains. The physiological role of PTP has not yet been resolved. The protein is present in very high concentration in pancreatic secretion and it has been detected in brain lesions in Alzheimer's disease and Down syndrome and in regenerating rat pancreatic islets. The present results provide a firm protein base for ongoing molecular, physical-chemical, and structure-function studies of this unusual protein.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01025016
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  • 4
    Electronic Resource
    Electronic Resource
    Further Alkaloids Common to Ants and Frogs: Decahydroquinolines and a Quinolizidine (1999)
    Springer
    Journal of chemical ecology 25 (1999), S. 1179-1193 
    Details
    ISSN: 1573-1561
    Keywords: Alkaloids ; mass spectrometry ; infrared spectroscopy ; amphibians ; ants ; decahydroquinolines ; quinolizidines
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract Three alkaloids—two minor decahydroquinolines (DHQs) and a major quinolizidine—were detected in an extract of a Brazilian myrmicine ant (Solenopsis (Diplorhoptrum) sp. picea group). One DHQ (3) was identical to a known frog-skin alkaloid, cis-195A (cis-5-methyl-2-propyldecahydroquinoline), while the second DHQ, an isomer of 3, designated 195J, was assigned a tentative cis-2-methyl-5-propyldecahydroquinoline structure (2) based on mass and infrared spectra. The third alkaloid proved identical to the frog-skin alkaloid 195C, for which a structure had not been previously proposed. Mass and infrared spectral analysis, including chemical ionization tandem mass spectrometry, indicated a 4-methyl-6-propylquinolizidine structure (1) for 195C. The four possible diastereomers were synthesized and the (6Z,10E)-4-methyl-6-propylquinolizidine diastereomer (1b) was identical to the natural alkaloid. Skin extracts of a population of a Madagascan mantelline frog contained, among other alkaloids, minor amounts of the same alkaloid triad 1–3 with 1 again predominating. The common occurrence of alkaloids 1–3 in both ant and frog supports the hypothesis that ants are a likely dietary source for sequestered frog-skin alkaloids and brings to six, the alkaloid classes common to ant and frog.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1020898229304
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  • 5
    Electronic Resource
    Electronic Resource
    Characterization of a single glycosylated asparagine site on a glycopeptide using solid-phase Edman degradation (1994)
    Springer
    Glycoconjugate journal 11 (1994), S. 180-186 
    Details
    ISSN: 1573-4986
    Keywords: N-terminal sequencing ; glycoprotein ; glycan analysis ; covalent immobilization ; mass spectrometry
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The characterization of site-specific glycosylation is traditionally dependent on the availability of suitable proteolytic cleavage sites between each glycosylated residue, so that peptides containing individual glycosylation sites are recovered. In the case of heavily glycosylated domains such as theO-glycosylated mucins, which have no available protease sites, this approach is not possible. Here we introduce a new method to gain site-specific compositional data on the oligosaccharides attached to a single amino acid. Using a model glycopeptide from a mutant human albumin Casebrook, glycosylated PTH-Asn was recovered after sequential solid-phase Edman degradation, subjected to acid hydrolysis and the sugars were identified by high performance anion exchange chromatography with pulsed amperometric detection. The PTH-Asn(Sac) derivative was further characterized by ionspray mass spectrometry. Comparison between an endoproteinase Glu-C glycopeptide and a tryptic glycopeptide showed that the oligosaccharide attached to Asn494 was stable after at least 10 cycles of Edman degradation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00731216
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  • 6
    Electronic Resource
    Electronic Resource
    Metabolism of 4-substituted-N-ethyl-N-methylanilines: Chromatographic and mass spectrometric identification of N-oxidation metabolic products formed in vitro (1982)
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 9 (1982), S. 233-240 
    Details
    ISSN: 0306-042X
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The electron impact and isobutane and ammonia chemical ionization mass spectral characteristics of the N-oxidation products of a series of 4-substituted-N-ethyl-N-methylanilines are described. The thermolability and the relative non-volatility of N-oxides of this type of tertiary aromatic amine makes their unequivocal identification by gas chromatography and electron impact mass spectrometry difficult. Mass spectral identification is facilitated by employing CI mass spectrometry where, under appropriate conditions, the N-oxides give intense protonated molecular ions. Chromatographic, electron impact and chemical ionization mass spectrometric evidence is presented which shows that these 4-substituted tertiary anilines undergo metabolic N-demethylation, N-de-ethylation and N-oxidation in vitro. The suitability of these tertiary aromatic amines as model substrates for mechanistic studies on C- and N-oxidation is discussed.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bms.1200090603
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  • 7
    Electronic Resource
    Electronic Resource
    Degradation of steroid derivatives at a gas chromatograph mass spectrometer interface (1982)
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 9 (1982), S. 505-509 
    Details
    ISSN: 0306-042X
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Methyloxime trimethylsilyl ether derivatives are frequently employed in gas chromatographic and mass spectrometric analysis of steroids. Under certain instrumental conditions, unusual mass spectra were recorded from some corticosteroid methyloxime trimethylsilyl ether derivatives, reflecting degradation by contact of the steroids with active surfaces in the gas chromatograph mass spectrometer interface. This occurred prior to electron impact ionization. Fragmentations of the degradation products of methyloxime trimethylsilyl ether derivatives of tetrahydrocortisol and tetrahydrodeoxycorticosterone are described, as representatives of C21 steroids with dihydroxyacetone and α-ketol side chains. Elemental compositions of ions were confirmed by high resolution mass spectrometric analysis. Derivatives of steroids with glycerol side chains, e.g. cortolone, showed no evidence of degradation. The problem was overcome by ensuring inertness of the glass restrictor interface and by preventing, as far as posssible, contact of sample with metal surfaces in the source housing.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bms.1200091202
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  • 8
    Electronic Resource
    Electronic Resource
    A comparison of thermospray and direct liquid introduction high-performance liquid chromatography/mass spectrometry for the analysis of candidate antimalarials (1984)
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 11 (1984), S. 616-621 
    Details
    ISSN: 0306-042X
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The analysis of antimalarials by high-performance liquid chromatography (HPLC)/mass spectrometry demonstrates a new dimension in specificity along with increased sensitivity compared to conventional HPLC detection methods. Both direct liquid introduction and thermospray HPLC/mass spectrometry interfaces provided molecular weight information as well as characteristic fragment ions for antimalarials not normally amenable to direct probe or gas chromatographic/mass spectrometric techniques. The direct liquid introduction interface, which incorporated a 1/100 split, showed a detection limit of 30 ng using selected ion monitoring. The thermospray technique showed less than 1 ng detection limits using selected ion monitoring.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bms.1200111205
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  • 9
    Electronic Resource
    Electronic Resource
    Metabolic N-oxidation of 3-substituted pyridines: Identification of products by mass spectrometry (1978)
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 5 (1978), S. 551-556 
    Details
    ISSN: 0306-042X
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The mass spectral characteristics of the N-oxides of a range of 3-substituted pyridines, and of quinoline and isoquinoline, are described. The molecular ion is the base peak in the majority of cases, provided that thermolysis is minimized when using the direct probe or gas chromatograph inlets. Chromatographic and mass spectral evidence is presented which indicates that biological oxidation of the heteroaromatic nitrogen of 3-substituted pyridines is a route of metabolism in vivo and in vitro.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bms.1200050909
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  • 10
    Electronic Resource
    Electronic Resource
    Dimesitylboryl compounds. VII - mass spectrometric studies (1981)
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 16 (1981), S. 467-468 
    Details
    ISSN: 0030-493X
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/oms.1210161012
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