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  • 1
    Electronic Resource
    Electronic Resource
    Melanin Biosynthesis From Dopamine. II. A Mass Spectrometric and Collisional Spectroscopic Investigation (1992)
    Oxford, UK : Blackwell Publishing Ltd
    Periodontology 2000 5 (1992), S. 0 
    Details
    ISSN: 1600-0757
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Electron impact (EI) and fast atom bombardment (FAB) mass spectrometry together with collisional activation (CA) experiments were applied to the study of the oxidation pathway of dopamine by tyrosinase. In order to prevent attachment of the protein to the highly reactive intermediates, ultrafiltration was employed to remove the enzyme at different reaction times. FAB, privileging molecular species formation, was successfully used for identification of transient intermediates and their relative concentrations with respect to time, directly in the reaction mixture. The presence of isobaric molecular species made chromatographic separation necessary. Further EI mass spectrometry and collision spectroscopy led to structural identification of pure components. Of these, dopamine-o-quinone, leucoaminochrome, and aminochrome semiquinone were characterized for the first time as real intermediates in dopamine melanogenesis, in agreement with previous hypotheses.This approach elucidated the pathway of dopamine melanogenesis.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1600-0749.1992.tb00008.x
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  • 2
    Electronic Resource
    Electronic Resource
    Fast Atom Bombardment Mass Spectrometry in the Study of Dopamine Melanogenesis Intermediates (1990)
    Oxford, UK : Blackwell Publishing Ltd
    Periodontology 2000 3 (1990), S. 0 
    Details
    ISSN: 1600-0757
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Fast atom bombardment was applied to the study of the intermediates of the reaction dopamine-tyrosinase after treatment with diazomethane. The identification of trimeth-oxyindoline, dopamine-o-quinone and dimethoxyindole was easily achieved by this ionization method, together with accurate mass measurements and collision experiments. The structures of these compounds are in agreement with those already hypothesized in studies on melanogenesis.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1600-0749.1990.tb00287.x
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  • 3
    Electronic Resource
    Electronic Resource
    Collision-induced dissociation of some protonated peptides with and without mass selection (1994)
    New York, NY : Wiley-Blackwell
    Rapid Communications in Mass Spectrometry 8 (1994), S. 274-279 
    Details
    ISSN: 0951-4198
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: Collision-induced dissociation (CID) of several protonated peptides formed by positive-ion electrospray (ES+) and by Cs+ fast-ion bombardment are reported. The CID spectra of ions formed by the first ionization method were effected at elevated extraction cone voltages within the ion source of a single quadrupole instrument, while linked-fields-scan measurements at constant B/E of ions formed by the latter technique were performed within the collision cell of a trisector instrument. For molecular masses below 1000 Da, the two sets of spectra yielded identical sequencing information; however, for higher molecular masses the similarity was less evident. This divergence between the two sets of measurements is partially attributed to dominant doubly charged ions and less efficient dissociation of sodium adduct ions at elevated cone voltages.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/rcm.1290080310
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  • 4
    Electronic Resource
    Electronic Resource
    Identification of phospholipid molecular species containing two fatty acyl chains differing by 2 Da by negative-ion fast-atom bombardment with mass-analyzed ion kinetic energy analysis (1992)
    New York, NY : Wiley-Blackwell
    Rapid Communications in Mass Spectrometry 6 (1992), S. 454-458 
    Details
    ISSN: 0951-4198
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: Isomeric glycerophosphatidylcholine molecular species containing fatty acyl chains differing by 2 Da (1-stearoyl-2-oleoyl- and 1-oleoyl-2-stearoyl-sn-glycero-3-phosphocholine) can be identified by the determination of trhe fatty acid chain esterified to the sn-1 position in the glycerol backbone based on the electric sector voltage differences of [M-86-R2COOH]- anions derived from phosphatidic acid parent ions (M minus choline group) produced by negative-ion fast-atom bombardment combined with mass-analyzed ion kinetic evergy analyses. Three volt differences can be observed in the spectra. The study further demonstrates that this approach is also effective in distinguishing such molecular species as isomers of glycerophosphatidic acid, glycerophosphatidyl-ethanolamine and glycerophosphatidylserine and in characterizing the molecular species, differing by 2 Da, of the bovine brian glycerophosphatidylserine (1-stearoyl-2-oleoyl-sn-glycero-3-phosphoserine) and the rabbit kidney glycerophos-phatidylethanolamine (1-oleoyl-2-linoleoyl-sn-glycero-3-phosphoethanolamine).
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/rcm.1290060710
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  • 5
    Electronic Resource
    Electronic Resource
    Effects of target identity and collision energy on the fragmentation of some mass-selected protonated neuropeptides (1993)
    New York, NY : Wiley-Blackwell
    Rapid Communications in Mass Spectrometry 7 (1993), S. 989-993 
    Details
    ISSN: 0951-4198
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: A number of protonated neuropetides formed by 10 keV Cs+ ion bombardment are mass selected and their collision-induced dissociations (CID) with helium, argon, xenon and isobutane are monitored using a collision energy of 200 eV. Data obtained by fixing the collision gas and using translational energies in the range 50-250 eV are also presented. The present data imply that optimzation of the CID spectra presented can be achieved through a judicious choice of both the target gas and the translational energy of the mass-selected ion. The combined effect of the two experimental parameters on the relative abundances of the major sequence ions and on the loss of side-chain moieties is discussed.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/rcm.1290071105
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  • 6
    Electronic Resource
    Electronic Resource
    Investigation of crudes of synthesis of [Leu31, Pro34]-neuropeptide Y by capillary zone electrophoresis/mass spectrometry (1995)
    New York, NY : Wiley-Blackwell
    Rapid Communications in Mass Spectrometry 9 (1995), S. 1386-1390 
    Details
    ISSN: 0951-4198
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: [Leu31, Pro34]-Neuropeptide Y is a thirty-six amino-acid peptide which has a measured relative molecular mass of 4222. Solid-phase synthesis of this peptide resulted in complex crudes of synthesis which were examined by capillary zone electrophoresis (CZE)/electrospray ionization mass spectrometry (ES-MS). The separation efficiency of CZE combined with the mass specificity of mass spectrometry yielded rapid and reliable information on the target peptide and a number of associated side products, which were mainly acetylated peptide sequences having relative molecular masses in the range 2240-4101. Such incomplete or, as they are commonly called, difficult sequences are provoked by problems of swelling and aggregation of the growing peptide chains in the course of synthesis. The use of mass spectrometry is indispensable for obtaining reliable information on the inevitable side products. Initial tuning of the ion source and optimization of the coupling between the CZE system and the mass spectrometer were achieved by performing a number of measurements pertaining to artificially made mixtures of commercial neuropeptides.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/rcm.1290091412
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  • 7
    Electronic Resource
    Electronic Resource
    A mass spectrometric investigation of mono-, di- and trimethylenebis (disphenylphosphine)- Pt(II)-cis-dichloro and -dicyano derivatives (1991)
    New York, NY : Wiley-Blackwell
    Rapid Communications in Mass Spectrometry 5 (1991), S. 479-483 
    Details
    ISSN: 0951-4198
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: The mass spectrometric behaviour of mono-, di- and trimethylenebis(diphenylphosphine)-Pt(II)-cis-dichloro and -dicyano drivatives has been studied with the aid of two different ionization techniques (electron ionization and fast-atom bombardment) and metastable ion studies, with the aim of finding the most suitable mass spectrometric technique for determining the real monomeric or dimeric structure of such compounds. Electron ionization mass spectrometry led to the best results in terms of molecular ion identification and production of fragment ions well-related to the original structure. On the contrary, fast-atom bombardment led to the formation of dimeric species for Pt{1,2-bis(diphenylphosphino)methane}Cl2 and Pt{1,2-bis(diphenylphosphino)methane}(CN)2 due to the high reactivity of the monomeric molecules in the condensed phase.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/rcm.1290051012
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  • 8
    Electronic Resource
    Electronic Resource
    Letter to the Editor (1994)
    New York, NY : Wiley-Blackwell
    Rapid Communications in Mass Spectrometry 8 (1994), S. 287-288 
    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.1290080312
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  • 9
    Electronic Resource
    Electronic Resource
    Investigation of complexes between some glycopeptide antibiotics and bacterial cell-wall analogues by electrospray- and capillary zone electrophoresis/electrospray-mass spectrometry (1995)
    New York, NY : Wiley-Blackwell
    Rapid Communications in Mass Spectrometry 9 (1995), S. 883-887 
    Details
    ISSN: 0951-4198
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: Complexation in aqueous solutions between vancomycin, ristocetin A, teicoplanin and two bacterial cell-wall analogues, Ac2-L-Lys-D-Ala-D-Ala (tripeptide) and Ac-D-Ala-D-Ala (dipeptide) has been examined by positiveion electrospray mass spectrometry (ES-MS) and capillary zone electrophoresis (CZE)/ES-MS. The ES-MS data demonstrate that as well as complexes between monomeric antibiotics and either peptide, the investigated solutions contained complexes ranging from the simple homodimer of the antibiotic to a more complex association giving ions of the type [2(antibiotic)+3(tripeptide)+3H]3+. The same data also demonstrate that the homodimers of the investigated antibiotics are significantly suppressed in the presence of the tripeptide. The use of CZE/ES-MS made it evident that the complexes between the antibiotic and the tripeptide were present in the solution prior to their introduction into the ion source. The two sets of data are compared with existing UV difference spectroscopy and nuclear magnetic resonance data on complexation and dimerization.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/rcm.1290091004
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  • 10
    Electronic Resource
    Electronic Resource
    Capillary zone electrophoresis/mass spectrometry: Analytical need or an option? (1995)
    New York, NY : Wiley-Blackwell
    Rapid Communications in Mass Spectrometry 9 (1995), S. 1325-1327 
    Details
    ISSN: 0951-4198
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/rcm.1290091320
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