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  • 1
    Electronic Resource
    Electronic Resource
    Tandem mass spectrometry of peptides using hybrid and four-sector instruments: A comparative study (1991)
    s.l. : American Chemical Society
    Analytical chemistry 63 (1991), S. 1473-1481 
    Details
    ISSN: 1520-6882
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/ac00014a024
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Electroencephalograph variables, drug concentrations and sedation scores in children emerging from propofol infusion anaesthesia (2004)
    Oxford, UK : Blackwell Publishing Ltd
    Pediatric anesthesia 14 (2004), S. 0 
    Details
    ISSN: 1460-9592
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Background : Inadequate sedation or oversedation are common problems in Paediatric Intensive Care because of wide variations in drug response and the lack of objective tests for sedative depth. We undertook a pilot study to try to identify correlates of propofol drug concentration, electroencephalographic (EEG) variables and observed behaviour during a stepwise reduction in propofol infusion after paediatric cardiac surgery.Methods : This was a prospective pilot study with 10 children (5 months to 8 years) emerging from propofol anaesthesia following cardiac surgery with cardiopulmonary bypass (CPB). Patients underwent a stepped wake-up from propofol anaesthesia during which the propofol infusion rate was decreased from 4 mg·kg−1·h−1 in 1 mg·kg−1·h−1 steps at 30 min intervals. EEG variables, propofol blood concentrations and clinical sedation scores (COMFORT scale) were recorded during the stepped wakeup. Analgesia was maintained with a standardized continuous infusion of fentanyl.Results : Mean (sd) whole blood propofol concentrations at arousal varied considerably [973 ng·ml−1 (sd 523 ng·ml−1)]. The summed ratio (SR) of high frequency to low frequency bands correlated with both propofol infusion rate (R2 value = 0.47) and propofol blood concentrations (R2 value = 0.64). The mean SR in deeply sedated patients was significantly different from that in the 5 min prior to wakening (6.84 vs 1.55, P = 0.00002). There was no relationship between COMFORT scores and SR.Conclusions : In this group of patients receiving opioid analgesia and relatively high doses of propofol, sedation scores were unhelpful in predicting arousal. The SR correlated with propofol blood concentrations and clinical arousal and may have potential as a predictive tool for arousal in children.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1460-9592.2003.01175.x
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  • 3
    Electronic Resource
    Electronic Resource
    Elucidation of some fragmentations of small peptides using sequential mass spectrometry on a hybrid instrument (1989)
    New York, NY : Wiley-Blackwell
    Rapid Communications in Mass Spectrometry 3 (1989), S. 217-221 
    Details
    ISSN: 0951-4198
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: Sequential daughter-ion-scanning analyses of small peptides have been performed using a hybrid tandem instrument of BEqQ configuration. Precursor ions are selected by B and allowed or induced (by high-energy collisional activation) to decompose in the region preceding E. Decoupling of E from the accelerating voltage permits the selection of the first-generation daughter ion whilst retaining appropriate float voltages for the quadrupole assemblies. The daughter ion selected by E is further subjected to low-energy collisional-activation dissociation (CAD) in q and the fragment-ion spectrum is obtained by scanning Q. The sequential daughter-ion-scanning technique has been used to establish that ‘internal’ fragments of the types, (AY′) and (BY′), are formed via initial Y-type cleavage. Fragmentation of a protonated peptide (angiotensin III) by loss of the C-terminal amino acid residue, yielding a (Bn′ + OH) ion, is reported for the first time. This process is analogous to that previously described for metal-cationized peptides.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/rcm.1290030704
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  • 4
    Electronic Resource
    Electronic Resource
    Approaches to the improvement of quantitative precision in selected ion monitoring: High resolution applications (1984)
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 11 (1984), S. 415-420 
    Details
    ISSN: 0306-042X
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A MAT 731 mass spectrometer has been modified to permit multiple ion monitoring at resolutions of 8000-10 000. The greater imprecision in response ratio (analyte/internal standard) determinations which accompanies the increase in mass spectrometric resolution is attributable to the weaker signal detected, rather than to instrument instability. The mass spectrometer has been coupled to a microprocessor-based data system and software prepared to facilitate the precise determination of response ratios. Imprecision is markedly reduced when isotope ratios are determined by linear regression analyses of signals attributable to the two ionic species detected.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bms.1200110810
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  • 5
    Electronic Resource
    Electronic Resource
    Preparation and tandem mass spectrometric analyses of deuterium-labeled cysteine-containing leukotrienes (1990)
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 19 (1990), S. 465-474 
    Details
    ISSN: 1052-9306
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Leukotrienes (LT) C4, E4 and N-acetyl-E4, their respective monomethyl esters and 14,15-2H2 analogs have been synthesized. The collisionally activated decompositions of the [ M + H] + and [ M - H] - ions formed by fast atom bombardment (FAB) have been studied by tandem mass spectrometry using a hybrid sector/quadrupole instrument. Structurally informative product ion spectra were obtained for each analyte; the fragmentation pathways proposed are consistent with the parallel data obtained for labeled and derivatized species. Fragmentation of [ M + H] + ions occurs prominently via cleavage of the thioether linkage with charge retention on the cysteine-containing (predominant for LTC4) or lipid-derived (predominant for LTE4) moieties. More pronounced differences were observed between the fragmentations of [ M - H] - ions derived from LTC4 and LTE4; the preference for charge retention, however, parallels that observed for the fragmentation of [ M + H] + ions. Selected ion monitoring during continuous-flow FAB mass spectrometric analysis of authentic LTC4 indicated a low-picogram detection limit.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bms.1200190804
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  • 6
    Electronic Resource
    Electronic Resource
    Dual metastable peak monitoring: Application to the analysis of oestradiol-17β as the bis (tert-butyldimethylsilyl) ether (1985)
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 12 (1985), S. 19-24 
    Details
    ISSN: 1052-9306
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A new approach to dual metastable peak monitoring has been developed, based on synchronous switching of the accelerating voltage and electric sector voltage of a double-focusing mass spectrometer. The technique has been applied to the determination of oestradiol-17β as the bis(tert-butyldimethylsilyl) ether, using the 2H3 analogue as internal standard. The detection limit was approximately 5 pg during monitoring of the [M]+.→[M-C4H9]+ fragmentation. Analyses of plasma extracts indicated that greater selectivity of detection was achieved during metastable peak monitoring than during high resolution (8000) selected ion monitoring of the parent ion.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bms.1200120105
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  • 7
    Electronic Resource
    Electronic Resource
    Evaluation of smoothing routines for the optimization of selected ion monitoring data (1986)
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 13 (1986), S. 605-609 
    Details
    ISSN: 1052-9306
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The effect has been investigated of data smoothing on the precision and accuracy of peak height ratio (analyte/isotopically-labelled internal standard) determination by gas chromatography/mass spectrometry with dual ion monitoring. The smoothing routines evaluated were all based on the moving average principle but differed with respect to weighting factors and filter width. Smoothing was shown to achieve only a minor improvement in precision and introduced significant bias in the peak height ratio calculation. In contrast, determination of response ratios by linear regression of analyte and internal standard signals achieved superior precision without the introduction of significant bias.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bms.1200131105
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