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  • 1
    Electronic Resource
    Electronic Resource
    The integrated molecular transform as a correlation parameter (1990)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 38 (1990), S. 27-34 
    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: The molecular transform is an alternate means of considering numerical representations of molecules in a manner designed to generate indices that can be related to structural and physiochemical parameters. The literature has shown that the transform, actually the Fourier transform, is operable on representations such as Cartesian coordinates or graphically derived depictious reflected by adjacency or distance matrices. The resulting curve may be used to give a binary index of the molecule or integrated to give an area-related index; either of these indices may be used as a correlation parameter in structure-activity studies. In this instance the individual bond distance matrices of a series of structurally diverse compounds served as input for a transform program. The derived index was then used to correlate both physical property and pharmacological activity indices for the series; correlation coefficients were comparable to those reported for the valence molecular connectivity parameter of Kier and Hall. The study also showed that lower correlation coefficients resulted when the index was based on the transform of hydrogen-suppressed structures.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560381706
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  • 2
    Electronic Resource
    Electronic Resource
    Proton transfer and triol formation in the simulation of GABA solvation (1988)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 34 (1988), S. 593-600 
    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: γ-Aminobutyric acid (GABA) is an inhibitory transmitter used by interneurons in the central nervous system (CNS). In aqueous solution GABA exists as a zwitterion, but in the gas phase the stable form of GABA is a nonzwitterion. Since zwitterions are difficult to transport into the CNS, details of the mechanism for the transformation between nonzwitterionic and zwitterion forms of GABA provide potentially important suggestions for enhancing transport of GABA and GABA analogues into the CNS. A mechanism for the conversion of GABA into the zwitterion form upon aqueous solvation is suggested as a multistage process by simple quantum chemical simulation. Initially, hydrogen bonding at the carbonyl oxygen is followed by attack of water at the carbonyl carbon and results in the formation of a triol. Hydrogen bond bridging, through solvent, from the triol end of the molecule to the amino terminus, facilitates N-protonation from the solvent. The latter appears to trigger rearrangement of the hydrogen bonding at the triol function, thus giving the anionic precursor to the zwitterion. This mechanism is based upon full INDO calculations using a supermolecule composed of GABA and 14 water molecules and resembles part of one of the mechanisms for the hydrolysis of esters as well as a process for the hydration of aldehydes.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560340863
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  • 3
    Electronic Resource
    Electronic Resource
    Molecular symmetry and closed-shell SCF calculations. I (1977)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 11 (1977), S. 613-625 
    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: For efficient integral evaluation, orbital basis functions are grouped into shells and integrals into blocks in the recently developed SCF program Hondo. This shell structure is ideally suited to the scheme of Dacre and Elder for using point group symmetry. An entire block of two-electron integrals is eliminated if it is symmetrically equivalent to another block with a higher index (four label). Using the “petite list” of blocks of integrals, a skeleton Fock matrix is formed from which the true Fock matrix is generated by “symmetrization.” We prove two theorems which provide a clear and rigorous justification for this version of the Dacre-Elder procedure. We compare SCF calculations on the phosphorus molecule using Td symmetry with those using various subgroups of Td. The number of integrals computed is found to be approximately inversely proportional to the order of the group. Integral evaluation time and SCF iteration time are each linear functions of the number of integrals. The computer spends a negligible amount of time in executing symmetry-related code, and the human effort involved is little more than picking the appropriate Schönflies symbol for the molecule.
    Additional Material: 2 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560110408
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  • 4
    Electronic Resource
    Electronic Resource
    Graph theory in the study of metal cluster bonding topology: Applications to metal clusters having fused polyhedra (1986)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 30 (1986), S. 227-238 
    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: The energy levels in a delocalized two- or three-dimensional chemical structure are related to the eigenvalues of the graph representing the corresponding bonding topology. Such relatively crude but computationally undemanding graph theory-derived models provide a clear demonstration of the close relationship between two-dimensional aromatic systems such as benzene and three-dimensional aromatic systems such as deltahedral boranes, carboranes, and metal clusters. The basic building blocks for the three-dimensional aromatic systems are deltahedra, having no degree 3 vertices. Delocalized bonding in such systems having v vertices requires two electrons for a multicenter core bond as well as 2v electrons for pairwise surface bonding. A problem of particular interest is how metal cluster polyhedra can fuse together, leading ultimately to the infinite structures of the bulk metals. As a model for such processes the fusion of rhodium carbonyl octahedra is examined using graph theory-derived methods. These lead to reasonable electron-precise models for the bonding topologies in the “biphenyl analogue” [Rh12(CO)30]2-, the “naphthalene analogue” [Rh9(CO)19]3-, the “anthracene analogue” H2Rh12(CO)25, and the “perinaphthene analogue” [Rh11(CO)23]3-. Similar models can also be developed for clusters based on centered larger rhodium polyhedra as exemplified by the centered cuboctahedral clusters of the type [Rh13(CO)24H5-q]q- (q = 2, 3, 4) representing a fragment of the hexagonal close-packed metal structure.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560300722
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  • 5
    Electronic Resource
    Electronic Resource
    Structure-pKa correlation via the integrated molecular transform (1995)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 56 (1995), S. 201-206 
    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: The integrated molecular transform (FTm) is a unitary structure index that has been successfully used for the correlation of 2- and 3-dimensional structure representations with their physicochemical and pharmacological properties. In the present instance the reported pKa values in a series of 30 compounds consisting of five subseries were correlated with their FTm indices. The omission of four outliers gave a moderate correlation across the entire series; within the individual subseries the correlations were considerably improved even with inclusion of the outliers. In general, the logarithmic transform of the pKa did not improve the correlations. This method gives a relatively simple means of estimating pKa in several structure classes. © 1995 John Wiley & Sons, Inc.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560560721
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  • 6
    Electronic Resource
    Electronic Resource
    Correlation of dermal transport with structure via the integrated molecular transform (1996)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 60 (1996), S. 1845-1849 
    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: The integrated molecular transform, FTm, is a unitary structure index that has been successfully used for the correlation of two- and three-dimensional structure representations with their physicochemical and pharmacological properties; it has also been shown to be a unique conformational descriptor. In the present instance correlation trials were undertaken by regressing reported molecular skin permeability values on their respective calculated three-dimensional FTm indices. The index functioned not only as a structure descriptor but as a natural delineator in the series, separating several outliers in the data set and showing that excellent correlations may be obtained within the classical divisions of chemical structure. These results not only provide a means of estimating skin permeability directly from structure but also may have theoretical implications for studies of the nature and mechanism of dermal transport. © 1996 John Wiley & Sons, Inc.
    Additional Material: 4 Ill.
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  • 7
    Electronic Resource
    Electronic Resource
    Dimensional response of the integrated molecular transform (1991)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 40 (1991), S. 289-297 
    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: The integrated molecular transform provides a unitary chemical structure index that is useful in quantitative structure-activity/property studies. The transform is generated by a Fourier operation on any one of several different matrices of structure representation, e.g., adjacency, bond count, distance between bonded atoms (termed 2-dimensional [2-D]), and distance between all atoms in a molecule (termed 3-dimensional [3-D]). In this study, the integrated transforms based on bond count and 2-D and 3-D structure matrices have been generated and used to correlate an enthalpy function and heats of formation in a series of linear and branched hydrocarbons; these indices were also compared with the 3-D Wiener number and Randić branching indices for the series. For the linear regression model, the branching and 3-D Wiener indices correlate the enthalpy function best, but the 2-D molecular transform is most appropriate for heats of formation. A normalized linear model shows that the 3-D Wiener number and 2-D molecular transform are most appropriate for the former data, whereas the latter is most effectively correlated with the 2-D molecular transform. For reasons not clear, the 3-D molecular transform is a less suitable index for the noted thermodynamic functions in this series.
    Additional Material: 7 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560400726
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  • 8
    Electronic Resource
    Electronic Resource
    Molecular transform quantization of enzyme surface probes (1992)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 44 (1992), S. 179-185 
    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: Inhibition of enzyme function by series of appropriate substrates is the first step in the classical approach to definition of the reactive or binding sites on an enzyme surface. Several years ago, M. I. Kabachnik and his colleagues published inhibition rate data for acetylcholinesterase (AChE) and butyrylcholinesterase (BuChE) by phosphonates and phosphates. Some of the phosphonate data has been reexamined from a structure-activity point of view using the square root of the integrated molecular transform as a unitary structure descriptor. Linear regressions showed good correlation in the BuChE case; less adequate correlation were manifested with the AChE data. This is attributable to the predominantly lipophilic nature of the interaction between BuChE and substrates as compared to AChE, where electronic factors may have a prominent role. The correlation further suggest a different, but nontrivial, mode of action between the respective enzymes and their substrates. © 1992 John Wiley & Sons, Inc.
    Additional Material: 4 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560440717
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  • 9
    Electronic Resource
    Electronic Resource
    Correlation of the partition coefficient with the molecular transform index in series of organophosphorus compounds (1994)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 52 (1994), S. 209-214 
    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: The molecular transform index (FTm) is a unitary representation of a molecule based on a Fourier operation on the bond distance or graphical descriptor matrices of the structure while incorporating the atomic number of the constituent atoms. In a series consisting of phosphonates, phosphonothionates, and a phosphinate, the FTm gave an excellent linear correlation (R = 0.91) with experimentally determined octanol/water partition coefficients (log Po/w). In a second group containing phosphonofluoridates, thionophosphonofluoridates, and phosphoramidofluoridates, the FTm correlation with log Po/w, calculated by the π-fragment method, served to separate the fluoridates and amidates as structural subclasses. © 1994 John Wiley & Sons, Inc.This article is a U.S. Government work and, as such, is in the public domain in the United States of America.
    Additional Material: 2 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560520717
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  • 10
    Electronic Resource
    Electronic Resource
    The inverse molecular transform index: A descriptor for molecular similarity analysis (1993)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 48 (1993), S. 139-145 
    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: The fast Fourier transform of a free-induction decay curve generated by a Fourier operation on a bond distance matrix representation of a molecule gives a frequency domain spectrum that, when plotted as a line of points, is similar to a chromatogram and is called the inverse molecular transform. Within a series of compounds including lower alkanes, alkenes, cyclics, heteroalipathics, and aromatics, the amplitude of the transform ordinates increased directly with the size of the molecule and with going from straight chain to cyclic structures with the same number of carbon atoms. A derived transform index gave a unitary numerical structure descriptor that was used in a topological comparison of structures and is called the transform similarity ratio. With further investigation, this methodology appears to have the potential to generate correlation descriptors, other molecular similarity measures, or an index of protein globularity. © 1993 John Wiley & Sons, Inc.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560480716
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