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  • Computational Chemistry and Molecular Modeling
  • Molecular Sequence Data
  • 1990-1994  (17)
  • 1990  (17)
  • 1
    Electronic Resource
    Electronic Resource
    Density functional calculations with simulated annealing - isomers of S7X [X = O, S, Se], Se8, O8 (1990)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 38 (1990), S. 141-151 
    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: Density functional calculations - with a local density approximation for the exchange and correlation energy - provide a numerically efficient method for determining total energy variations in molecules. Coupled with molecular dynamics techniques such as simulated annealing, they provide a scheme for probing large regions of configuration space in molecules. We outline the main features of the method and apply it to different ring isomers of S7O, S8, S7Se, Se8, and O8.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560382417
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  • 2
    Electronic Resource
    Electronic Resource
    A CI pseudopotential-based description of the low-lying states of Ag O2 (1990)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 37 (1990), S. 785-796 
    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: Extensive SCF-LCAO-MO variational and perturbative configuration interaction (CI) calculations framed within an effective core potential approximation have been performed to determine the two experimentally observed geometrical isomers of Ag O2 and the interconversion route between them. These structural forms, associated to the ground-state local minima, yield virtually the same energy, and their spontaneous interconversion is strongly indicated, which agrees fairly well with the experimental measurements. The reaction Ag + O2 → Ag O2 was theoretically analyzed along a CI fully optimized energy pathway for the ground and various excited states, within C2v and Cs symmetry. Although a tight-ion pair (Ag+ O2-) character is predicted for the ground state at the equilibrium geometries, its dissociation leads to neutral rather than to ionic fragments. The study of the reaction path within Cs symmetry shows an avoided crossing between the ground state and another 2A″ potential curve where the former correlates adiabatically with the reactants Ag(2S) + O2(1Δg). This indicates that the formation of the complex proceeds via a reactive state of molecular oxygen. The higher 2A″ electronic curves correlate with the metal 2P excited state, and the oxygen binding is found to be less favorable. The present results are shown to have an important bearing on the experimentally known catalytic properties of oxygen adsorbed on silver surfaces.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560370607
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  • 3
    Electronic Resource
    Electronic Resource
    Exploring the potential energy hypersurface of histamine monocation: Tautomerism in gas phase (1990)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 38 (1990), S. 727-740 
    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 potential energy hypersurface of the histamine monocation is determined by ab initio methods at the STO-4G level using analytical gradient techniques. Three transition states and two minima have been found for the Nτ—H tautomer. One of the transition states connects the trans conformational region with a minimum gauche structure, where the proton of the ammonium group is approximately halfway between the Nπ of the imidazole group and the N of the ammonium group, but nearer to the Nπ. This minimum connects the potential energy surface of the Nτ—H tautomer with the imidazolium one. In the latter region, three transition states and two minima have been found. Critical points are discussed in relation with experimental data and histamine H2 receptor models.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560380513
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  • 4
    Electronic Resource
    Electronic Resource
    Comparability graphs and molecular properties III. C9 and C10 alkanesRefs. 1 and 2 for Parts I and II of this series. (1990)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 37 (1990), S. 135-153 
    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 graph-theoretical approach recently developed for comparing and ordering isomeric chemical compounds is extended and applied to the calculation of various molecular properties of C9 and C10 alkanes (critical densities, volumes, and pressures; heats and entropies of vaporization; standard entropies in liquid and gas state). The key to the approach is in specifying subsets of comparable isomers which are located in the same paths in the so-called comparability graphs. Optimized samples for structure-property correlations are thus obtained.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560370205
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  • 5
    Electronic Resource
    Electronic Resource
    Classical dynamical analysis of the vibrational spectra for small polyatomic molecules (1990)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 38 (1990), S. 429-446 
    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: With the study of three specific molecules, Na3(C2E″), HCN(X1Σ+), and O3(D1B2), each showing a distinctly different dynamical behavior at the energies studied, we show how techniques of nonlinear classical mechanics can be applied to simulate low resolution vibrational spectra and to extract the underlying dynamics from them. Particularly the importance of the single unstable periodic orbits in the chaotic regions of phase space is demonstrated.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560382443
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  • 6
    Electronic Resource
    Electronic Resource
    A conformational study of cocaine and its diastereomers (1990)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 11 (1990), S. 1111-1118 
    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: A conformational study of cocaine and its three diastereomers, pseudococaine, allococaine, and allopseu-dococaine was carried out using molecular mechanics and quantum mechanical semiempirical techniques. Molecular dynamics simulations were performed at high temperature to scan their conformational space. Additional molecular dynamics at 312 K were used to explore the conformational flexibility of the compounds around the minimum energy conformation at physiologically relevant temperatures. The AM1 technique was used to refine the description of the minimum energy structures obtained with the molecular mechanics technique and to compute the electronic properties of cocaine and its diastereoisomers. Comparison of the results obtained with previous NMR and X-ray structural data was carried out. The structural information obtained was then used to discuss some aspects of the pharmacology of cocaine and other compounds that bind at the site recognized by it on the dopamine transporter.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jcc.540110915
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  • 7
    Electronic Resource
    Electronic Resource
    The nature of the N — H…O=C hydrogen bond: An intermolecular perturbation theory study of the formamide/formaldehyde complex (1990)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 11 (1990), S. 1217-1233 
    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: We have used Hayes-Stone Intermolecular Perturbation Theory (IMPT) to study the variation with distance and orientation of the various components of the interaction energy of the N — H…O = C hydrogen bonded trans- formamide/formaldehyde complex, a model system for hydrogen bonding in proteins. The directionality of the total interaction energy is similar to that of the electrostatic component alone. We have analysed our data in terms of two model atom-atom intermolecular potentials, using an isotropic functional form and an anisotropic one. The anisotropic form gives an excellent representation of the IMPT potential energy surface, considerably better than the isotropic model, and is comprised entirely of theoretically justified, physically meaningful terms.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jcc.540111014
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  • 8
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    Kinetics of gramicidin channel formation in lipid bilayers: transmembrane monomer association (1990)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 1990-11-30
    Description: Conducting gramicidin channels form predominantly by the transmembrane association of monomers, one from each side of a lipid bilayer. In single-channel experiments in planar bilayers the two gramicidin analogs, [Val1]gramicidin A (gA) and [4,4,4-F3-Val1]gramicidin A (F3gA), form dimeric channels that are structurally equivalent and have characteristically different conductances. When these gramicidins were added asymmetrically, one to each side of a preformed bilayer, the predominant channel type was the hybrid channel, formed between two chemically dissimilar monomers. These channels formed by the association of monomers residing in each half of the membrane. These results also indicate that the hydrophobic gramicidins are surprisingly membrane impermeant, a conclusion that was confirmed in experiments in which gA was added asymmetrically and symmetrically to preformed bilayers.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉O'Connell, A M -- Koeppe, R E 2nd -- Andersen, O S -- GM21342/GM/NIGMS NIH HHS/ -- GM34968/GM/NIGMS NIH HHS/ -- New York, N.Y. -- Science. 1990 Nov 30;250(4985):1256-9.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Physiology and Biophysics, Cornell University Medical College, New York, NY 10021.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/1700867" target="_blank"〉PubMed〈/a〉
    Keywords: Amino Acid Sequence ; Cell Membrane Permeability ; Chemistry, Physical ; Electric Conductivity ; Gramicidin/*chemistry/metabolism ; Ion Channels/*chemistry/physiology ; Kinetics ; Lipid Bilayers/*chemistry ; Macromolecular Substances ; Molecular Sequence Data ; Physicochemical Phenomena ; Protein Conformation
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
    Published by American Association for the Advancement of Science (AAAS)
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  • 9
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    Two G protein oncogenes in human endocrine tumors (1990)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 1990-08-10
    Description: Somatic mutations in a subset of growth hormone (GH)-secreting pituitary tumors convert the gene for the alpha polypeptide chain (alpha s) of Gs into a putative oncogene, termed gsp. These mutations, which activate alpha s by inhibiting its guanosine triphosphatase (GTPase) activity, are found in codons for either of two amino acids, each of which is completely conserved in all known G protein alpha chains. The likelihood that similar mutations would activate other G proteins prompted a survey of human tumors for mutations that replace either of these two amino acids in other G protein alpha chain genes. The first gene so far tested, which encodes the alpha chain of Gi2, showed mutations that replaced arginine-179 with either cysteine or histidine in 3 of 11 tumors of the adrenal cortex and 3 of 10 endocrine tumors of the ovary. The mutant alpha i2 gene is a putative oncogene, referred to as gip2. In addition, gsp mutations were found in 18 of 42 GH-secreting pituitary tumors and in an autonomously functioning thyroid adenoma. These findings suggest that human tumors may harbor oncogenic mutations in various G protein alpha chain genes.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Lyons, J -- Landis, C A -- Harsh, G -- Vallar, L -- Grunewald, K -- Feichtinger, H -- Duh, Q Y -- Clark, O H -- Kawasaki, E -- Bourne, H R -- New York, N.Y. -- Science. 1990 Aug 10;249(4969):655-9.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Human Genetics, Cetus Corporation, Emeryville CA 94608.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/2116665" target="_blank"〉PubMed〈/a〉
    Keywords: Amino Acid Sequence ; Base Sequence ; DNA, Neoplasm/genetics ; Endocrine System Diseases/*genetics ; Female ; GTP Phosphohydrolases/genetics/metabolism ; GTP-Binding Proteins/*genetics/metabolism ; Humans ; Male ; Molecular Sequence Data ; *Mutation ; Neoplasms/*genetics ; Oligonucleotide Probes ; *Oncogenes ; Pituitary Neoplasms/*genetics ; Polymerase Chain Reaction
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
    Published by American Association for the Advancement of Science (AAAS)
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  • 10
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    Characterization of naturally occurring minor histocompatibility peptides including H-4 and H-Y (1990)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 1990-07-20
    Description: Minor histocompatibility (H) antigens can be peptides derived from cellular proteins that are presented on the cell surface by major histocompatibility complex (MHC) class I molecules. This is similar to viral antigens, because in both cases cytotoxic T lymphocytes (CTLs) recognize artificially produced peptides loaded on target cells. Naturally processed minor H peptides were found to be similar to those artificial CTL-epitopes, as far as size and hydrophobicity is concerned. The peptides studied were isolated from a transfectant that expressed a model CTL-defined antigen, beta-galactosidase, from male cells that express H-Y, which has been known operationally since 1955, and from cells that express H-4, known since 1961.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Rotzschke, O -- Falk, K -- Wallny, H J -- Faath, S -- Rammensee, H G -- New York, N.Y. -- Science. 1990 Jul 20;249(4966):283-7.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Max-Planck-Institut fur Biologie, Abteilung Immungenetik, Tubingen, Federal Republic of Germany.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/1695760" target="_blank"〉PubMed〈/a〉
    Keywords: Amino Acid Sequence ; Animals ; Epitopes/isolation & purification ; Female ; H-Y Antigen/*analysis/immunology ; Male ; Mice ; Mice, Inbred Strains ; Minor Histocompatibility Antigens/*analysis/immunology ; Molecular Sequence Data ; Peptides/chemical synthesis ; Species Specificity ; Spleen/immunology ; T-Lymphocytes, Cytotoxic/*immunology
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
    Published by American Association for the Advancement of Science (AAAS)
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