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  • Analytical Chemistry and Spectroscopy  (174)
  • 1995-1999  (174)
Collection
Keywords
Publisher
Years
Year
  • 1
    Electronic Resource
    Electronic Resource
    Periodic and chaotic precipitation phenomena in bile salt system related to gallstone formation (1997)
    New York, NY [u.a.] : Wiley-Blackwell
    Biospectroscopy 3 (1997), S. 195-205 
    Details
    ISSN: 1075-4261
    Keywords: cholelithiasis ; gallstone ; bile salts ; periodic precipitation ; fractal precipitation ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Physics
    Notes: This is the first observation that both chaotic and periodic patterns are formed in metal ions-deoxycholate-gel systems. It is an in vitro model for approximating the conditions present during gallstone formation. The experimental results suggest that a nonlinear scientific concept such as the “butterfly effect” should be considered in understanding gallstone formation. This effect suggests that a butterfly flapping its wings in Beijing today may lead to a thunderstorm in New York months later. Applying this concept to biology, minor changes in the local chemical environment within biological systems may lead to large variations in the structure and morphology of gallstone through changes in the behavior of biological mineralization process. © 1997 John Wiley & Sons, Inc. Biospect 3: 195-205, 1997
    Additional Material: 13 Ill.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Ionophores: Potential screening via supercritical-fluid chromatography combined with mass spectrometry and tandem mass spectrometry (1995)
    New York, NY : Wiley-Blackwell
    Rapid Communications in Mass Spectrometry 9 (1995), S. 712-716 
    Details
    ISSN: 0951-4198
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: A variety of ionophores have been studied by packed column supercritical-fluid chromatography combined with mass spectrometry. One of the ionophores, lasalocid, provided particularly good multiple-reaction monitoring signal-to-noise responses when analysed by tandem mass spectrometry and this approach shows considerable potential for the analysis of this compound in medicated animal feeds. A capillary supercritical-fluid chromatograph has been interfaced to an unmodified benchtop quadrupole mass spectrometer and this combination has enabled the molecular weight determination of the sodium salt of an ionophore.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/rcm.1290090816
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  • 3
    Electronic Resource
    Electronic Resource
    EXAFS and FTIR studies on the binding of deoxycholic acid with copper and zinc ions (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Biospectroscopy 1 (1995), S. 291-296 
    Details
    ISSN: 1075-4261
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Physics
    Notes: Deoxycholic acid is an important physiological bile acid. The binding of bile salts with metal ions has received more attention due to its clinical significance. In this study, a series of copper and zinc deoxycholate complexes were synthesized. EXAFS and FTIR spectroscopic techniques were used for characterization. The results indicated that both the carboxyl and hydroxyl groups of deoxycholic acid are binding to the Cu (or Zn) ion to form a new complex. There are six oxygen atoms surrounding the metal ion with the average bond lengths of Cu-O and Zn-O are 1.95 and 2.06 Å respectively. © 1995 John Wiley & Sons, Inc.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bspy.350010407
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  • 4
    Electronic Resource
    Electronic Resource
    Ultrafast infrared spectroscopy in biomolecules: Active site dynamics of heme proteins (1996)
    New York, NY [u.a.] : Wiley-Blackwell
    Biospectroscopy 2 (1996), S. 277-299 
    Details
    ISSN: 1075-4261
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Physics
    Notes: Rapid advances in the generation of intense tunable ultrashort mid-infrared (IR) laser pulses allow the use of ultrafast IR pump-probe and vibrational echo experiments to investigate the dynamics of the fundamental vibrational transition of CO bound to the active site of heme proteins. The studies were performed using a free-electron laser (FEL) and an experimental set up at the Stanford University FEL Center. These novel techniques are discussed in some detail. Pump-probe experiments on myoglobin-CO (MbCO) measure CO vibrational relaxation (VR). The VR process involves loss of vibrational excitation from CO to the protein and solvent. Infrared vibrational echoes measure CO vibrational dephasing. The quantum mechanical treatment of the force-correlation function description of vibrational dynamics in condensed phases is described briefly. A quantum mechanical treatment is needed to explain the temperature dependence of VR in Mb-CO from 10 to 300 K. A molecular-level description including elements of heme protein structure in the treatment of vibrational dynamics is also discussed. Vibrational relaxation of CO in Mb occurs on the 10-11-s time scale. VR was studied in proteins with single-site mutations, proteins from different species, and model heme compounds. A roughly linear relationship between carbonyl stretching frequency and VR rate has been observed. The dominant VR pathway is shown to involve anharmonic coupling from CO through the π-bonded network of the porphyrin, to porphyrin vibrations with frequencies 〉 400 cm-1. The heme protein influences VR of bound ligands at the active site primarily via altering the through π-bond coupling between CO and heme. Preliminary vibrational echo studies of the effects of protein conformational relaxation dynamics on ligand dephasing are also reported. © 1996 John Wiley & Sons, Inc.
    Additional Material: 12 Ill.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    The Townes and Dailey approach to the interpretation of NQR parameters in the light of non-empirical calculations. Three-membered rings (1995)
    Chichester : Wiley-Blackwell
    Organic Magnetic Resonance 33 (1995), S. 761-766 
    Details
    ISSN: 0749-1581
    Keywords: non-empirical calculations ; NQR parameters ; Townes and Dailey theory ; three-membered rings ; LMO approach ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The nuclear and electronic contributions to the EFG tensor components eqii at 14N, 17O, 33S and 35Cl nuclei in aziridine, methylaziridine, chloroaziridine, oxirane and thiirane were determined. The nuclear contributions were calculated within classical representations, while electronic contributions were calculated non-empirically using a 6-31G* basis set within the framework of the LMO approach. On the basis of the analysis of the contributions to the EFG tensor components from definite bond and lone-pair orbitals, the main concepts of the Townes and Dailey approach were tested.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mrc.1260331002
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  • 6
    Electronic Resource
    Electronic Resource
    Mass spectrometric investigations of some N-cycloalkyl and N-aryl fluoroacetamidesPresented at the 13th Informal Meeting on Mass Spectrometry: Budapest 8-10 May 1995. (1995)
    New York, NY : Wiley-Blackwell
    Rapid Communications in Mass Spectrometry 9 (1995), S. 954-956 
    Details
    ISSN: 0951-4198
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: The electron-ionization induced mass spectra of some N-monosubstituted fluoroacetamides of the general formula FCH2—CONH—R, in which the substituent R is (C3—C7) cycloalkyl, phenyl, 4-methylphenyl, 4-carbo-methoxyphenyl, 4-nitrophenyl and 4-diethylaminophenyl, were recorded and their fragmentation patterns were studied by metastable-ion analyses.
    Additional Material: 2 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/rcm.1290091017
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  • 7
    Electronic Resource
    Electronic Resource
    Collision-induced dissociation of C60-: Effect of energy-coupling processes on the dissociation dynamics (1995)
    New York, NY : Wiley-Blackwell
    Rapid Communications in Mass Spectrometry 9 (1995), S. 114-118 
    Details
    ISSN: 0951-4198
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: Dissociation of C60- ions induced in 30 keV collisions with atomic and molecular gases has been studied. The pattern of negativeion formation from C60- precursors is found to be distinctly different from that obtained for positive-ion fragments from C60+ precursors in that the collision-induced dissociation spectrum in the former case is dominated by small negative clusters, presumably of linear geometry, Simple arguments utilizing the relationship of electrostatic properties of different molecular structures to their electron affinities and ionization energies have been invoked to rationalize these observations. The difference in the dissociation dynamics of C60- and C60+ ions is discussed in terms of competition between different energy-coupling schemes involving either electronic degrees of freedom or nuclear (vibrational) degrees of freedom.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/rcm.1290090203
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  • 8
    Electronic Resource
    Electronic Resource
    Comparison of the mass spectrometric behaviour of fluorinated ethers and sulphides (1995)
    New York, NY : Wiley-Blackwell
    Rapid Communications in Mass Spectrometry 9 (1995), S. 1376-1379 
    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 two pairs of fluorinated vinyl- and allyl-ethers and thioethers has been studied in detail with the aid of metastable ion data and accurate mass measurements. Clear differences have been observed between the two sets of compounds; while for the ethers the McLafferty rearrangement with ethylene loss represents a highly favoured decomposition route, for the thioethers the loss of the ethyl radical is preferred. Some decomposition routes, common to all the compounds examined, suggest the presence of hydrogen atom bridging between carbon and fluorine atoms. Theoretical calculations have shown that such a quasi C—H—F structure is already present in the neutral molecule in its ground state.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/rcm.1290091410
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  • 9
    Electronic Resource
    Electronic Resource
    Mass fragmentographic assay for 25-hydroxyvitamin D in plasma without derivatization: Enhanced sensitivity for metabolites of vitamins D2 and D3 after pre-column dehydration (1995)
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 30 (1995), S. 348-356 
    Details
    ISSN: 1076-5174
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: A mass fragmentographic method for the measurement in plasma of underivatized, dehydrated 25-hydroxyvitamin D2 and 25-hydroxyvitamin D3 was developed. Quantitative dehydration of vitamin D metabolites was achieved prior to gas chromatography using a new high-temperature injection system and a small precolumn packed with aluminium powder in the injection port, followed by mass fragmentography on an inexpensive bench-top mass spectrometer. Plasma (2 ml) was incubated with hexadeuteriated 25-hydroxyvitamin D3 prior to acetonitrile extraction and purification using cartridges pre-packed with microparticulate silica using reversed- and normal-phase solvent systems. After purification, capillary gas chromatography mass spectrometry was carried out following dehydration of the secosteroids on the aluminium power pre-column at 400°C. High-intensity dehydrated molecular ions were produced which were used for selected ion monitoring. The assay sensitivity for 25-hydroxyvitamin D was approximately 1 ng ml-1. The intra-assay variation was less than 7% and the recovery of added standard was quantitative. It is suggested that this method may be used to provide target values for much needed quality control schemes to monitor assays routinely used in the estimation of 25-hydroxyvitamin D. The behaviour of a number of other hydroxylated vitamin D metabolites, when injected without derivatization on to a gas chromatographic column, was also investigated.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jms.1190300218
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  • 10
    Electronic Resource
    Electronic Resource
    Profiling 19-norsteroids. II - tandem mass spectrometric characterization of the heptafluorobutyryl ester and pentafluorobenzyloxime heptafluorobutyryl ester derivatives of 19-norandrosterone using collisionly activated dissociation (1995)
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 30 (1995), S. 505-510 
    Details
    ISSN: 1076-5174
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Tandem mass spectrometric methods for the identification of 19-norandrosterone (3α-hydroxy-5α-estran-17-one) are described and evaluated. The fragmentation reactions of the heptafluorobutyryl (HFB) and pentafluorobenzyloxime heptafluorobutyryl (PFBO—HFB) ester derivatives of 19-norandrosterone (3α-hydroxy-5α-estran-17-one) in particular were studied for the purpose to select characteristic ions. The HFB ester was analyzed by collisionly activated dissociation (CAD) following electron impact in order to fragment the steroid nucleus. The formation of D-ring fragments, i.e. the ring containing the keto function, was typical for this type of derivative. Cleavages of fragments with an intact D-ring were also prominent. The PFBO—HFB ester was formed to create a derivative, which could capture electrons and be analyzed in the Electron Capture Negative Chemical Ionization (ECNCI) mode. Besides fragmentations originating in the groups coupled to the steroid by derivatization, also characteristic D-ring fragments were observed by CAD following ECNCI. Accordingly, of both methods evaluated only CAD following EI of the HFB derivative of 19-norandrosterone provided a characteristic MS/MS procedure for the identification of 19-norandrosterone under the conditions studied.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jms.1190300317
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