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  • Analytical Chemistry and Spectroscopy  (48)
  • Biochemistry  (5)
  • NMR  (5)
  • 11
    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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  • 12
    Electronic Resource
    Electronic Resource
    Black canyons for ions stored in an ion-trap mass spectrometer (1992)
    New York, NY : Wiley-Blackwell
    Rapid Communications in Mass Spectrometry 6 (1992), S. 573-578 
    Details
    ISSN: 0951-4198
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: Effects from higher order non-linear resonances, ‘black canyons’, have been observed for ions stored within the quadrupole ion-trap mass spectrometer. At specific qz values, higher-order field effects were observed to cause decreased intensity of chemical ionization (CI) reagent ions, due to ineffcient storage, as well as collision-induced dissociation. Efects have been observed, whether or not the CI reagent ions are mass-selected, and exibit increased severity with longer storage times. Previous reports have shown ‘black holes’ due to inefficient storage of product ions in tandem (MS/MS) spectra, but have reported no such effects in normal mass spectra. Without employing resonant excitation, higher-order field effects were investigated and found to occur continuously along iso-βz lines for βz = 1/3, 1/2, and 2/3. Described in this paper are the directs from higher-order fields on ions stored at specific az values, and indirec effects by those ions. Also described in this paper is new evidence for ‘black canyons’ occurring at βz = 1/3 at negative az values.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/rcm.1290060908
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  • 13
    Electronic Resource
    Electronic Resource
    Quantitative relationships between the structure of β-adrenolytic and antihistamine drugs and their retention on an α1-acid glycoprotein HPLC column (1994)
    New York, NY : Wiley-Blackwell
    Biomedical Chromatography 8 (1994), S. 125-129 
    Details
    ISSN: 0269-3879
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: Chromatographic retention parameters of a series of 7 β-adrenolytics and of 12 antihistamine drugs were determined employing an α1-acid glycoprotein (AGP) high-performance liquid chromatographic (HPLC) column. For the group of antihistamines capillary electrophoretic (CE) retention was additionally measured in the presence of either AGP or human serum albumin (HSA). Two series of solutes hydrophobicity parameters were obtained by reversed-phase HPLC on an immobilized artificial membrane (IAM) column. The solutes studied were subjected to molecular modelling and the structural descriptors obtained were applied in studies of quantitative structure-retention (protein binding) relationships (QSRR). It was found that retention on AGP correlates well with the literature on physiological protein binding data. This retention was demonstrated to depend on hydrophobicity: to a lesser extent in the case of β-adrenolytics and strongly in the case of antihistamines. Hydrophobicity, along with molecular width and electron excess charge on aliphatic nitrogen was demonstrated to describe retention of antihistamines on AGP. The AGP column is recommended as a convenient reactor for studies of drug-protein interactions. Preliminary CE data do not correlate with the HPLC data.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bmc.1130080306
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  • 14
    Electronic Resource
    Electronic Resource
    Optimization of short-column gas chromatography/electron ionization mass spectrometry conditions for the determination of underivatized anabolic steroids (1992)
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 21 (1992), S. 420-430 
    Details
    ISSN: 1052-9306
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A gas chromatographic/mass spectrometric method based on the use of short capillary gas chromatograph columns (3-5 m) and electron ionization mass spectrometry has been optimized and evaluated for the determination of underivatized anabolic steroids. The short-column gas chromatographic/mass spectrometric method was shown to result in short analysis times and to require minimal sample preparation, but suffered from some loss in sensitivity and chromatographic resolution compared with conventional gas chromatographic/mass spectrometric techniques for derivatized steroids. Therefore, short-column gas chromatographic conditions were optimized to maximize the sample transfer efficiency (sensitivity) from the gas chromatograph into the ion source of the mass spectrometer, while maintaining chromatographic integrity and minimizing thermal decomposition. Mass spectrometric conditions were optimized to maximize ionization efficiency with respect to the intensity of the molcular ion and degree of fragmentation such that positive identication of each steroid could be made based on the resulting mass spectra. Under optimized conditons, we have shown that underivatized anabolic steroids spiked into urine samples can be determined at low-nanogram levels using short-column chromatography/full-scan electron ionization mass spectrometry.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bms.1200210903
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  • 15
    Electronic Resource
    Electronic Resource
    Chitosan coated capillary with reversed electroosmotic flow in capillary electrophoresis for the separation of basic drugs and proteins (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Microcolumn Separations 6 (1994), S. 403-407 
    Details
    ISSN: 1040-7685
    Keywords: chitosan ; reversed electroosmotic flow ; capillary electrophoresis ; basic drug enantiomers ; proteins ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: An enhanced surface coating method was developed for capillary electrophoresis (CE) using the natural polymer chitosan. The cationic property of chitosan at pH below 6.5 created a reversed electroosmotic flow (EOF) in the capillary. The EOF changed significantly with the run buffer pH at values below 4.0, with less pH dependency at values in the pH range of 4.0-5.5. The new coating exhibited good performance reproducibility. The relative standard deviation (RSD) of EOF was 0.77%. The EOF changed an average of 2.4% after 10 h normal use. The EOF started to change significantly after a constant electric field (300 v cm-1) had been applied for 20 h. This capillary with a reversed EOF can be used to reduce the solute-wall interaction problem for separations of basic analytes, for example, separations of positively charged proteins and basic drug enantiomers.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mcs.1220060409
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  • 16
    Electronic Resource
    Electronic Resource
    Short-column gas chromatography/tandem mass spectrometry for the detection of underivatized anabolic steroids in urine (1994)
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 23 (1994), S. 131-139 
    Details
    ISSN: 1052-9306
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Short-column (3.5 m) gas chromatography (GC)/tandem mass spectrometry (MS/MS) has been investigated for the detection of structurally related, underivatized anabolic steroids in urine. The approach described here demonstrates the ability to rapidly and qualitatively detect underivatized anabolic steroids in spiked urine matrices. In this approach, underivatized steroids are determined using a short-column GC separation, ionized by positive ion chemical ionization, and detected by selected reaction monitoring MS/MS. This approach permits positive identification of underivatized anabolic steroids based on retention time and the production of characteristic product ions. Preliminary detection limits studies in spiked urine samples showed quantitative results between 2 and 40 ng steroid per milliliter of urine. The potential advantages of this approach compared to present screening methods based on conventional (30 m) GC/MS are its rapidity and selectivity. Reliable qualitative identification can be performed with a short-column GC/MS/MS analysis of less than 6 min with a reduction in sample preparation time due to the elimination of the derivatization step.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bms.1200230303
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  • 17
    Electronic Resource
    Electronic Resource
    Direct database searching with MALDI-PSD spectra of peptides (1995)
    New York, NY : Wiley-Blackwell
    Rapid Communications in Mass Spectrometry 9 (1995), S. 1546-1551 
    Details
    ISSN: 0951-4198
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: The analysis of matrix-assisted laser desorption ionization post-source decay (MALDI-PSD) mass spectra of peptides by using the cross-correlation method for database searching is illustrated. MALDI-PSD mass spectra are shown to contain sufficient fragmentation information to uniquely identify the correct amino acid sequence from large protein databases (∼160000 entries). A search employing the MALDI-PSD mass spectrum of a phosphorylated peptide that correctly identifies the amino acid sequence and the site of phosphorylation is also illustrated.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/rcm.1290091515
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  • 18
    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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  • 19
    Electronic Resource
    Electronic Resource
    Femtosecond time-resolved spectroscopy of the primary photochemistry of phytochrome (1997)
    New York, NY [u.a.] : Wiley-Blackwell
    Biospectroscopy 3 (1997), S. 421-433 
    Details
    ISSN: 1075-4261
    Keywords: plant photoreceptor ; photoisomerization mechanism ; excited state lifetime ; fluorescence quantum yield ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Physics
    Notes: Time-resolved absorption spectra of Pr phytochrome were obtained using a regeneratively amplified femtosecond titanium : sapphire laser system. The early time transient absorption spectra are comprised of prompt Pr photobleaching, stimulated emission, and excited-state absorption features that decay with a 24 ps time constant that matches the ground state appearance time of the primary photoproduct. Based on the 5 ns radiative lifetime calculated from the absorption and spontaneous emission spectra and the fluorescence quantum yield of 5.5 (± 0.5) × 10-3, we calculate an excited-state lifetime of 28 ps that agrees well with the directly determined lifetime. The transient absorption spectra are consistent with a primary photochemical reaction quantum yield of 0.15, and the absorption spectrum of the primary photoproduct closely resembles that of the low-temperature trapped intermediate, lumi-R. We conclude that the primary photoisomerization, which is believed to be a Z,syn → E,syn isomerization of the C15=C16 chromophore bond, occurs in 24 ps. © 1997 John Wiley & Sons, Inc. Biospectroscopy 3: 421-433, 1997
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
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  • 20
    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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