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  • 1
    Electronic Resource
    Electronic Resource
    Prediction of the n-Octanol/Water Partition Coefficient, logP, Using a Combination of Semiempirical MO-Calculations and a Neural Network (1997)
    Springer
    Journal of molecular modeling 3 (1997), S. 142-155 
    Details
    ISSN: 0948-5023
    Keywords: Keywords: Partition coefficient ; logP ; AM1 ; PM3 ; QSAR ; neural netIntroduction
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract A back-propagation artificial neural net has been trained to estimate logP values of a large range of organic molecules from the results of AM1 and PM3 semiempirical MO calculations. The input descriptors include molecular properties such as electrostatic potentials, total dipole moments, mean polarizabilities, surfaces, volumes and charges derived from semiempirical calculated gas phase geometries. These properties can be related to the molecule′s solubility in hydrophilic or lipophilic media. The input descriptors were selected with the help of a multiple linear regression analysis. The resulting net estimates the logP values of 105 organic compounds with a standard deviation of 0.53 units from the experimental logP values for AM1 and 0.67 units in the case of PM3.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s008940050027
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  • 2
    Electronic Resource
    Electronic Resource
    A Semiempirical QM/MM Implementation and its Application to the Absorption of Organic Molecules in Zeolites (1999)
    Springer
    Journal of molecular modeling 5 (1999), S. 1-7 
    Details
    ISSN: 0948-5023
    Keywords: Keywords AM1 ; Semiempirical MO ; Hybrid method ; QM/MM ; Zeolites ; Absorption energies
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract An intermolecular hybrid semiempirical MO/molecular mechanics technique is described. The model allows polarisation of the quantum mechanical molecule(s), but not of the molecular mechanics part and is shown to be relatively insensitive to the size of the molecular mechanics environment. It has been validated by comparison of calculated and experimental absorption energies of small organic molecules in various zeolites. This validation gives us confidence that the method is also appropriate for experimentally less well characterised problems, such as solvation or ligand/enzyme complexation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s008940050100
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    A Detailed Study of VESPA Electrostatic Potential-Derived Atomic Charges (1995)
    Springer
    Journal of molecular modeling 1 (1995), S. 176-187 
    Details
    ISSN: 0948-5023
    Keywords: Keywords Computational chemistry, potential derived charges, orientational and conformational dependence
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract VESPA, an improved semiempirical method for the calculation of electrostatic potential-derived atomic charges has been tested. It is shown that this approach is even less dependent upon molecular orientation than "high density" CHELPG ab initio ESP-derived charges. The conformational dependence of VESPA charges has been investigated for rotation around the C-N bond in formamide and 11 different conformers of glycerolphosphorylcholine. The results obtained are also compared to the corresponding ab initio values. Finally, VESPA is used to calculate electrostatic potential-derived charges for bioorganic molecules. We discuss the abilities and the limitations of ESP charges in this area.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s008940050014
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  • 4
    Electronic Resource
    Electronic Resource
    Some biological applications of semiempirical MO theory (1998)
    Springer
    Perspectives in drug discovery and design 9-11 (1998), S. 131-159 
    Details
    ISSN: 1573-9023
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1027259921634
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  • 5
    Electronic Resource
    Electronic Resource
    VESPA: A new, fast approach to electrostatic potential-derived atomic charges from semiempirical methods (1997)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 18 (1997), S. 744-756 
    Details
    ISSN: 0192-8651
    Keywords: computational chemistry ; semiempirical MO methods ; ESP atomic charges ; QSAR ; Chemistry ; Theoretical, Physical and Computational Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: An improved semiempirical method for computing electrostatic potential-derived atomic charges is described. It includes a very fast algorithm for the generation of the grid points around the molecule and the calculation of the electrostatic potential at these points. The dependency of the atomic point charges obtained on the number of grid points used in the fitting procedure is examined. For “buried” atoms a high density grid is necessary. It is possible to obtain 6-31G*-quality atom-centered point charges, even for phosphorus compounds, using AM1 or PM3. This approach can therefore be recommended for general use in QSAR or molecular mechanics for any organic and bioorganic system up to about 200 atoms. © 1997 by John Wiley & Sons, Inc. J Comput Chem 18: 744-756, 1997
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
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    Paper (German National Licenses)
  • 6
    Electronic Resource
    Electronic Resource
    The natural atomic orbital point charge model for PM3: Multipole moments and molecular electrostatic potentials (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 15 (1994), S. 1064-1073 
    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 natural atomic orbital/point (NAO-PC) model originally developed to calculate molecular electrostatic potentials (MEPs) and multiple moments based on the AM1 wave function has been extended to PM3. As for AM1, NAO-PC/PM3 reproduces dipole moments calculated by the standard PM3 method very well. There is also a surprisingly good correlation between experimental and calculated quadrupole moments. The MEPs calculated using PM3/NAO-PC are found to be in better agreement with those given by RHF/6-31G* than those obtained from the PM3 wave function using Coulson charges. On the other hand, the NAO-PC model is often slightly worse then the method implemented in MOPAC-ESP. The MEPs calculated using our model based on the PM3 wave function are often in better agreement with those given by RHF/6-31G* than those obtain with AM1. © 1994 by John Wiley & Sons, Inc.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jcc.540151003
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    Paper (German National Licenses)
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