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  • 1
    Electronic Resource
    Electronic Resource
    Identification and quantitation of an oxidative metabolite of labetalol in sheep: Pharmacokinetic and metabolic implicationsSupported by a Medical Research Council of Canada Program Grant (PG-11120). (1992)
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 21 (1992), S. 534-540 
    Details
    ISSN: 1052-9306
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A sensitive and selective assay has been developed for the identification and quantitation of 3-amino-1-phenylbutane (3-APB), a metabolite of labetalol, in biological fluids using electron impact gas chromatography/mass-selective detection. Samples were extracted with n-hexane, derivatized with heptafluorobutyric anhydride and chromato-graphed on a cross-linked fused-silica capillary column. A positive EI spectrum was obtained using a mass-selective detector. Identification of the metabolite was accomplished using an authentic standard; quantitation was performed in the selected ion monitoring mode using ions m/z 345 (M+) and 132. The assay was linear over the calibration range of 0.5-1000 ng of the analyte and the intra-sample coefficients of variation were less than 12% in all cases. The absolute recovery of 3-APB following extracton from urine and bile was found to be 102.9 ± 4.9% and 98.3 ± 1.45% (mean ± SEM) respectively. The minimum quantitation limit of the assay was 0.5 ng ml-1 (≈ 2 pg injected). Application of the assay in a pharmacokinetic-pharmacodynamic study of labetalol in sheep is demonstrated. The metabolite was detected in urine and bile samples obtained from adult non-pregnant sheep following labetalol administration. The cumulative amount of 3-APB excreted in urine over 24 h was found to be 71.55 μg in one animal following a 100 mg dose of labetalol. Evidence for biliary excretion, glucuronidation and sulfation of 3-APB was also found.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bms.1200211103
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  • 2
    Electronic Resource
    Electronic Resource
    Screening techniques for the detection of inborn errors of bile acid metabolism by direct injection and micro-high performance liquid chromatography-continuous flow/fast atom bombardment mass spectrometry (1993)
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 22 (1993), S. 331-337 
    Details
    ISSN: 1052-9306
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Two methods, direct injection-continuous flow fast atom bombardment (DI-CF/FAB) mass spectrometry and micro-high-performance liquid chromatography (μHPLC)-CF/(FAB) mass spectrometry were developed for the clinical analysis of urinary bile acids and their conjugates, specifically for the diagnosis of disorders of bile acid metabolism. The method based upon DI of urine extracts into the CF/FAB flow stream was developed for the rapid screening of large numbers of patient samples. It allows injections to be made at 4 min intervals for high sample throughput. Analyses of standard mixtures of bile salts demonstrate that linear response curves are obtained over more than a hundred-fold concentration range with a minimum detectable amount in the picogram range. Oxo bile salts are identified by reduction with sodium borodeuteride followed by reanalysis for detection of any reduction products. This methodology has been used for the analysis of over 1000 specimens. A reverse-phase μHPLC-CF/FAB mass spectrometric method was also developed for use in the confirmation or further investigation of screening results. With no additional sample preparation this method permits the separation, identification and quantitation of urinary bile salt isomers within a 45 min analysis time.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bms.1200220604
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  • 3
    Electronic Resource
    Electronic Resource
    Time-base modulation for the correction of cyclotron frequency shifts observed in long-lived transients from fourier-transform ion-cyclotron-resonance mass spectrometry of electrosprayed biopolymers (1993)
    New York, NY : Wiley-Blackwell
    Rapid Communications in Mass Spectrometry 7 (1993), S. 700-703 
    Details
    ISSN: 0951-4198
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: The occurrence of small shifts in the cyclotron frequency during the acquisition of very long transients (in excess of 80 s) has been observed to be a limiting factor for ultrahigh-resolution mass measurements of protein ions performed with electrospray-ionization Fourier-transform ion-cyclotron-resonance mass spectrometry. Resolution measurements were restricted to values less than 106 because of the frequency shifts. Measurements of the frequency shifts, performed by sequentially transforming small segments of the transient, allowed the shift to be characterized and fitted to a 4th-order equation. The sampling rate of the acquired transient was then modulated (at a rate equal to the reciprocal of the rate for the frequency shift) to allow ultrahigh resolution, greater than 2 × 106, and improved mass measurement and precision to be achieved for a small protein.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/rcm.1290070803
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  • 4
    Electronic Resource
    Electronic Resource
    Selected-ion accumulation from an external electrospray ionization source with a fourier-transform ion cyclotron resonance mass spectrometer (1993)
    New York, NY : Wiley-Blackwell
    Rapid Communications in Mass Spectrometry 7 (1993), S. 914-919 
    Details
    ISSN: 0951-4198
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: The coupling of an electrospray ionization (ESI) source to a Fourier-transform ion cyclotron resonance (FTICR) mass spectrometer provides a facility for the high resolution, accurate mass analysis of large biopolymers. Typically the m/z range of the electrosprayed ions injected and trapped in the FTICR cell is between m/z 500 and 2500 (but can vary considerably with solution conditions). Recent reports on quadrupole excitation have demonstrated the ability to cool the magnetron motion of ions trapped in the FTICR mass spectrometer cell by converting this motion to cyclotron motion which, under appropriate pressure conditions, damps readily to the center of the cell. The use of a broadband waveform (swept frequency or stored waveform inverse Fourier-transform) for the quadrupole cooling pulse was shown to provide cooling of a wide range of m/z ions, while implementation of a single frequency demonstrated a much narrower m/z response. This report demonstrates the successful combination of single-frequency quadrupole cooling with external injection of electrosprayed ions into an FTICR mass spectrometer for m/z selected-ion accumulation. This capability is particularly significant with electrospray ionization since it allows ions of only one charge state to be accumulated in the cell, and greatly increases the potential dynamic range of ESI-FTICR.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/rcm.1290071012
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  • 5
    Electronic Resource
    Electronic Resource
    Electron impact ionization mass spectra of lithocholyl amides: Evidence for a C(20) to C(23) rearrangement involving the loss of a C4H9 fragment (1994)
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 29 (1994), S. 335-341 
    Details
    ISSN: 0030-493X
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Amides of lithocholic acid (3α-hydroxy-5β-cholan-24-oic acid) with 6-aminocaproic acid and 4-aminobutyric acid were prepared and examined by electron impact ionization mass spectrometry. Both these compounds gave an unusual [M - 57]+ fragment. Since the product-ion analysis of [M - 57]+ revealed the presence of fragments corresponding to the intact steroid nucleus in addition to that of the original amino acid (6-aminocaproic acid or 4-aminobutyric acid), we concluded that the integrity of the steroid amide had been retained in this fragment. The absence of this fragment from the product-ion spectrum of [M - CH3]+ rules out the sequential loss from the molecular ion of 15 + 42 u as the origin of this signal. Mass spectrometry of the 24-13C-labelled lithocholylcaproylamide showed the retention of the label in the [M - 57]+ fragment. In contrast, the corresponding compound labelled with deuterium at C(23) showed a significant loss of the label during the formation of this product ion at [M - 58]+. In addition, through a combination of derivatization and tandem mass spectrometry, it was demonstrated that this loss of 57 u represented a rearrangement with the expulsion of a C4H9 radical from the side-chain spanning C(20) to C(23) resulting in a truncated steroid-amide fragment. This fragmentation pattern has not been observed in bile acid conjugates with N-α-amino acids.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/oms.1210290702
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  • 6
    Electronic Resource
    Electronic Resource
    Proton NMR study of a non-covalent complex formed between cytochromé c peroxidase-cyanide and tuna ferricytochrome c (1993)
    Chichester : Wiley-Blackwell
    Organic Magnetic Resonance 31 (1993), S. S53 
    Details
    ISSN: 0749-1581
    Keywords: 1H NMR ; 2D NMR ; Cytochrome c complexes ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A non-covalent complex of cyanide-ligated cytochrome c peroxidase (CcPCN) with tuna ferricytochrome c, formed in low-concentration KNO3 solutions, was studied by proton NMR spectroscopy. Complex formation affects the ferricytochrome c spectrum similarly to the spectral changes previously observed for the corresponding complex formed using resting state cytochrome c peroxidase. The CcPCN-tuna ferricytochrome c complex studied here is also similar to the previously studied CcPCN complexes with both horse and yeast iso-1 ferricytochromes c. For this complex both proteins are in the low-spin iron(III) form, which make them both paramagnetic and causes severe overlap in the proton hyperfine resonance shift region. Two-dimensional proton NMR spectroscopy has been used to resolve this overlap and make proton resonance assignments. These results complete the set of experiments carried out on the complexes of CcPCN with three species of ferricytochrome c (hores, yeast and tuna) and reveal that as for the similar complexes of these ferricytochromes c with the resting-state, high-spin form of the peroxidase, the tuna results closely follow those of the horse ferricytochrome c complex. These results also extend preliminary work that revealed for the first time that cytochrome c binding was reflected in hyperfine resonance shifts of protons in the peroxidase heme pocket.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mrc.1260311312
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