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  • Analytical Chemistry and Spectroscopy  (8)
  • Computational Chemistry and Molecular Modeling  (6)
  • Wiley-Blackwell  (14)
  • 2005-2009
  • 1990-1994  (14)
  • 1
    Electronic Resource
    Electronic Resource
    Computer modelling of fragmentation processes in radio frequency multipole collision cells (1990)
    New York, NY : Wiley-Blackwell
    Rapid Communications in Mass Spectrometry 4 (1990), S. 186-197 
    Details
    ISSN: 0951-4198
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: To date, methods for calculating the trajectories of ions in radio frequency (RF) multipole fields have involved solving, analytically or numerically, the appropriate equations of motion. Another method is presented here whereby a non-ideal distribution of field may be modelled and the position of an ion can be tracked, as it traverses the multipole. The validity of the calculations is discussed and some of the properties of collision cells are explained. Fragmentation processes within the cell are modelled showing that the focusing properties within the cell have a striking effect on parent- and daughter-ion transmission.
    Additional Material: 24 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/rcm.1290040605
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  • 2
    Electronic Resource
    Electronic Resource
    Novel pentacoordinated bridged silicon anions (1992)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 44 (1992), S. 691-698 
    Details
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Both ab initio and semiempirical electronic structure calculations are used to investigate the molecular and electronic structures and eneregetic stabilities of an unusual bridged compound with the general formula [Y—SiH3—X—SiH3—Y]-, with Y = H or F and X = H, CH3, NH2, OH, F, or Cl. Most of these bridged anions are quite stable relative to YSiH3 + XSiH3Y-, and the stability is predicted to increase considerably when Y = H is replaced with Y = F.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560440503
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  • 3
    Electronic Resource
    Electronic Resource
    Calculating electrostatic forces from grid-calculated potentials (1990)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 11 (1990), S. 401-409 
    Details
    ISSN: 0192-8651
    Keywords: Computational Chemistry and Molecular Modeling ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: The accurate calculation of forces from finite difference potentials is very important, especially in the area of Brownian dynamics simulations. Test charge methods are typically used to calculate these forces. In these methods, the potential is calculated with one group of charges present, then the force on a second set of charges is calculated as the negative of the gradient of the potential times the charge. The test charge methods for calculating forces between solute molecules have been compared with more accurate methods and then regions of validity of the test charge methods explored. The test charge methods neglect certain reaction field effects. It is found for the simple charged systems studied that beyond a center-to-center separation of about twice the sum of the molecular radii the test charge approximations can be quite good. For polar molecules with no net charges, however, the corrections can be significant to even longer ranges.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jcc.540110315
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  • 4
    Electronic Resource
    Electronic Resource
    Dielectric boundary smoothing in finite difference solutions of the poisson equation: An approach to improve accuracy and convergence (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 12 (1991), S. 909-912 
    Details
    ISSN: 0192-8651
    Keywords: Computational Chemistry and Molecular Modeling ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: Finite difference methods are becoming very popular for calculating electrostatic fields around molecules. Due to the large amount of computer memory required, grid spacings cannot be made extremely small in relation to the size of the van der Waals radii of the atoms. As a result, the calculations make a rather crude approximation to the molecular surface by defining grid line midpoints discontinuously as either interior or exterior. We present a method which “smoothes” the boundary, but more accurately models the potential from the analytic solution of the discontinuous dielectric problem and improves convergence in electrostatic energy calculations. In addition, a small improvement in convergence rate is observed.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jcc.540120718
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  • 5
    Electronic Resource
    Electronic Resource
    Hydration of small anions: Calculations by the AM1 semiempirical method (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 12 (1991), S. 350-358 
    Details
    ISSN: 0192-8651
    Keywords: Computational Chemistry and Molecular Modeling ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: The AM1 semiempirical molecular orbital method has been used to calculate successive heats of hydration of small anions, including hydride, hydroxide, and the halogen ions, for cluster sizes up to 11 water molecules surrounding the central anion. Heats of hydration agree with available experimental data to within a few kcal/mol. Structures, however, do not always agree well with available ab initio calculations on clusters with one or two water molecules. The results indicate that the AM1 semiempirical technique applied to finite-sized clusters must be used with caution in understanding how hydration affects the chemical reactions of anions.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jcc.540120308
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  • 6
    Electronic Resource
    Electronic Resource
    Electrostatic energy calculations by a Finite-difference method: Rapid calculation of charge-solvent interaction energies (1992)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 13 (1992), S. 768-771 
    Details
    ISSN: 0192-8651
    Keywords: Computational Chemistry and Molecular Modeling ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: Finite-difference Poisson-Boltzmann (FDPB) methods allow a fast and accurate calculations of the reaction field (charge-solvent) energies for molecular systems. Unfortunately, the energy in the FDPB calculations includes the self-energies and the finite-difference approximation to the Coulombic energies as well as the reaction field energy. A second finite-difference calculation, in a uniform dielectric, is therefore necesssary to eliminate these contributions. In this article we describe a rapid and accurate method to calculate the self energy and finite-difference Coulombic energies in a uniform dielectric thus eliminating the need for a second finite-difference calculation. The computational savings for this method range from a factor of 4 for a typical protein to a factor of 103 for small molecules. © 1992 by John Wiley & Sons, Inc.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jcc.540130610
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  • 7
    Electronic Resource
    Electronic Resource
    Solving the finite-difference non-linear Poisson-Boltzmann equation (1992)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 13 (1992), S. 1114-1118 
    Details
    ISSN: 0192-8651
    Keywords: Computational Chemistry and Molecular Modeling ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: The Poisson-Boltzmann equation can be used to calculate the electrostatic potential field of a molecule surrounded by a solvent containing mobile ions. The Poisson-Boltzmann equation is a non-linear partial differential equation. Finite-difference methods of solving this equation have been restricted to the linearized form of the equation or a finite number of non-linear terms. Here we introduce a method based on a variational formulation of the electrostatic potential and standard multi-dimensional maximization methods that can be used to solve the full non-linear equation. © 1992 by John Wiley & Sons, Inc.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jcc.540130911
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  • 8
    Electronic Resource
    Electronic Resource
    Thermospray high performance liquid chromatography/mass spectrometric identification of a bladder carcinogen metabolite isolated from guinea pig urine (1990)
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 19 (1990), S. 601-608 
    Details
    ISSN: 1052-9306
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: An in vivo uninary metabolite of the bladder carcinogen 2-amino-4-(5-nitro-2-furyl) thiazole was isolated from guinea pig urine and was identified by direct analysis using thermospray mass spectrometry/high-performance liquid chromatography as 1-(2-amino-4-(5-nitro-2-furyl)-2-thiazolyl)-1-deoxy-β-D-glucopyranuronic acid. The structure of this metabolite was also established by chemical synthesis. Both positive and negative ion thermospray mass spectrometry of the conjugate showed fragment ions resulting from cleavage across the pyran ring of the glucuronic acid comprising of aglycone moiety. These characteristic fragment ions may be diagnostic for identification of N-glucuronides from O-glucuronides.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bms.1200191005
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  • 9
    Electronic Resource
    Electronic Resource
    Quantification of plasma phenylethylamine by combined gas chromatography/electron capture negative ion mass spectrometry of the N-acetyl-N-pentafluorobenzoyl derivative (1991)
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 20 (1991), S. 375-381 
    Details
    ISSN: 1052-9306
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: An ultrasensitive method capable of detection and quantification of β-phenylethylamine in 1 ml of human plasma has been developed using gas chromatography/electron capture negative ion mass spectrometry. Phenylethylamine and tetra-deutero phenylethylamine internal standard in plasma were acetylated, extracted into organic solvent and then further acylated with pentafluorobenzoyl chloride. The N-acetyl-N-pentafluorobenzoyl-phenylethylamines were detected by high-resolution single ion monitoring of the molecular ions. Normal plasma levels were found to be 41.5 ± 10.7 pg ml-1, in accordance with results of a previous high-performance liquid chromatographic method.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bms.1200200608
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  • 10
    Electronic Resource
    Electronic Resource
    Structural characterization by mass spectrometry of native and recombinant human relaxin (1990)
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 19 (1990), S. 655-664 
    Details
    ISSN: 1052-9306
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Mass spectrometry has played a key role in characterizing the primary structure of native and recombinant relaxin, a peptide hormone that induces ripening of the cervix prior to childbirth. The peptide is composed of two chains, A and B, and is formed from a single-chain prohormone, as is insulin. Aside from conserved cysteines, though, it has little sequence homology with insulin. Due to the small amounts of native peptide initially available ( 〈 10 pmol), traditional techniques could not provide information on the blocked A-chain sequence, on the carboxy-terminal sequences, nor on other possible post-translational modifications. Mass measurements by fast atom bombardment (FAB) were made on reduced human relaxin isolated from corpora lutea. The detection limit by FAB for reduced relaxin was 500 fmol. The B-chain was four amino acids shorter than expected from comparison of the previously known cDNA sequence with homologous rat and porcine sequences. The A-chain, as predicted, was 24 amino acids in length and had a pyroglutamic acid residue on the amino-terminus. The purified samples were homogeneous with no other post-translational modifications. The recombinant relaxin molecule was also extensively characterized by mass spectrometry. In addition to the intact molecule, all tryptic peptides were characterized by FAB. A capillary high-performance liquid chromatography continuous-flow FAB system, developed for high-sensitivity peptide mapping, aided in these analyses. Finally, the three disulfide bonds were shown by tandem mass spectrometry to match those of insulin.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bms.1200191105
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