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  • Analytical Chemistry and Spectroscopy  (174)
  • Wiley-Blackwell  (174)
  • 2005-2009
  • 1995-1999  (174)
  • 1
    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.
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  • 2
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Rapid Communications in Mass Spectrometry 9 (1995), S. 712-716 
    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.
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  • 3
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Biospectroscopy 1 (1995), S. 291-296 
    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.
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  • 4
    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.
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  • 5
    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.
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  • 6
    ISSN: 0935-6304
    Keywords: Capillary electrophoresis ; Mass spectrometry ; Electrospray ionization ; Fourier transform ion cyclotron ; Resonance ; Biomolecule analysis ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: We describe the current state of the on-line combination of capillary electrophoresis (CE) electrospray ionization (ESI) Fourier transform ion cyclotron resonance (FTICR) mass spectrometry (MS), and discuss aspects of the FTICR technique relevant to its use as a detection scheme for on-line separations. Aspects including sensitivity, mass resolution, duty cycle, and tandem mass spectrometric capabilities are discussed in the context of online separations with examples from the authors' laboratory.
    Additional Material: 6 Ill.
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  • 7
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Biospectroscopy 1 (1995), S. 149-156 
    ISSN: 1075-4261
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Physics
    Notes: A series of copper bilirubinate complexes (CuBR) was synthesized in solution and in solid state to mimic the black color of the black-pigment gallstone and to explore the formation mechanism of the gallstonein vitro. The variation of the copper contents of these samples indicated that CuBR also exhibits nonstoichiometric characteristics from the FTIR study, i.e., both the so-called acid and neutral copper complex moieties exist in CuBR. The NH groups in pyrrole and lactam groups of bilirubin (H2BR) are binding to the copper ions. An EPR study demonstrates the generation of free radicals and the variation of its electronic structure and conjugation system in the skeleton of H2BR molecule during complex formation. A polymer of CuBR may form through the reaction of H2BR with copper ions. © 1995 John Wiley & Sons, Inc.
    Additional Material: 5 Ill.
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  • 8
    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.
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  • 9
    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-nortestosterone (estr-4-en-17β-3-one) are described and evaluated. The fragmentation reactions of the heptafluorobutyryl (HFB) and pentafluorobenzyloxime heptafluorobutyryl (PFBO—HFB) ester derivatives of 19-nortestosterone 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. Cleavage of the A-ring, i.e. the ring containing the keto function, was prominent. The formation of A-, A/B- and D-ring fragments was also typical for this type of derivative. 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, no prominent steroid nucleus fragmentations were observed by CAD following ECNCI. Accordingly, of both methods only CAD following EI of the HFB derivative of 19-nortestosterone provided a characteristic MS/MS procedure for the identification of 19-nortestosterone.
    Additional Material: 5 Ill.
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  • 10
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Rapid Communications in Mass Spectrometry 9 (1995), S. 114-118 
    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.
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