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  • Chemistry  (76)
  • Inorganic Chemistry  (16)
  • Atomic, Molecular and Optical Physics  (6)
  • Human impact  (3)
  • Density functional calculations  (2)
  • Molecular dynamics  (2)
  • Transition states  (2)
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  • 1
    Electronic Resource
    Electronic Resource
    Relativistic density-functional studies of naked and ligated gold clusters (1994)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 52 (1994), S. 595-610 
    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: Electronic structure investigations on a broad range of gold compounds, including naked and ligated gold clusters, are reviewed. The calculations have been carried out with a recently introduced relativistic variant of the linear combination of Gaussian-type orbitals density-functional (LCGTO-DF) method which affords all-electron investigations for very large systems. The accuracy of the method will be evaluated for the gold dimer. Then the electronic structure of the naked cluster Au55 is studied, both in Ih and Oh symmetry. Nonrelativistic and relativistic results obtained by the present method are compared to those of the much simpler jellium model. Since triphenylphosphine is among the most common ligands in gold chemistry a series of mononuclear gold phosphine compounds MeAuPR3 with increasingly complex ligands PR3 (R = H, CH3, C5H6) is discussed. The calculations reveal the success and the limitations of simpler phosphines often employed as model ligands in theoretical studies. Some aspects of the phosphine gold interaction in these simpler compounds carry over to the main group element centered gold clusters. Thereby one arrives at a rationalization of the particularly high stability of the carbon-centered octahedral cluster cation [(R3PAu)6C]2+ as compared to the neighboring isoelectronic boron and nitrogen-centered clusters. © 1994 John Wiley & Sons, Inc.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560520853
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  • 2
    Electronic Resource
    Electronic Resource
    Conformation of the Flavin Adenine Dinucleotide Cofactor FAD in DNA-Photolyase: A Molecular Dynamics Study (1998)
    Springer
    Journal of molecular modeling 4 (1998), S. 73-82 
    Details
    ISSN: 0948-5023
    Keywords: Keywords  FAD ; Photolyase ; Molecular dynamics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract   In order to gain insight into the light-driven repair of DNA by the enzyme DNA photolyase, the conformation of the photoactive cofactor FAD, a flavin adenine dinucleotide, has been studied by molecular dynamic simulations. In contrast to FAD in the gas phase and in water where the MD procedure yields various "open" I-shaped as well as "closed" U-shaped conformations, the calculations of FAD binding to the enzyme show essentially a single U-shaped conformation of this cofactor which, so far, is unique among FAD-carrying proteins. It is characteristic for this U-shaped conformation that the FAD components occupy opposite sides of the pocket in the surface of the protein which provides the binding site for the defect pyrimidine dimer structure on DNA. In fact, the calculated U-shaped conformation is very close to the one revealed by the X-ray structure analysis of DNA photolyase. Moreover, the simulations yield details on the binding of the photoactive isoalloxazine moiety and the dynamics of the amino acids forming the binding cavity of the enzyme.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s008940050133
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  • 3
    Electronic Resource
    Electronic Resource
    The structure of ColE1 rop in solution (1991)
    Springer
    Journal of biomolecular NMR 1 (1991), S. 71-82 
    Details
    ISSN: 1573-5001
    Keywords: rop ; Protein conformation ; 2D NMR ; Molecular dynamics ; Repressor proteins
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Summary The structure of the ColE1 repressor of primer (rop) protein in solution was determined from the proton nuclear magnetic resonance data by a combined use of distance geometry and restrained molecular dynamics calculations. A set of structures was determined with low internal energy and virtually no violations of the experimental distance restraints. Rop forms homodimers: Two helical hairpins are arranged as an antiparallel four helix bundle with a left-handed rope-like twist of the helix axes and with left-handed bundle topology. The very compact packing of the side chains in the helix interfaces of the rop coiled-coil structure may well account for its high stability. Overall, the solution structure is highly similar to the recently determined X-ray structure (Banner, D.W., Kokkinidis, M. and Tsernoglou, D. (1987)J. Mol. Biol.,196, 657–675), although there are minor differences in regions where packing forces appear to influence the crystal structure.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01874570
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  • 4
    Electronic Resource
    Electronic Resource
    Prehistoric land use as recorded in a lake-shore core at Lake Constance (1993)
    Springer
    Vegetation history and archaeobotany 2 (1993), S. 213-232 
    Details
    ISSN: 1617-6278
    Keywords: Human impact ; Lake Constance ; Neolithic ; Bronze Age ; Climate
    Source: Springer Online Journal Archives 1860-2000
    Topics: Archaeology , Biology
    Notes: Abstract The second part of a pollen profile from Hornstaad/Lake Constance (Germany), containing the Atlantic and Subboreal (6400 cal B.C. to 700 cal B.C.) is presented. The diagram has a sampling interval of 1 cm and an average time resolution of 10 years. The cereal curve provided the basis for cereal zones, which are used to classify the human impact. Twenty-six cereal zones can be distinguished, most of them divided into subzones, from 5500 cal B.C. to 700 cal B.C. They correspond to both known and, mostly, unknown settlements in the surrounding landscape from the Early Neolithic to the Late Bronze Age. Charcoal and chemical analyses as well as sediment accumulation, confirmed by accelerator dates, provide evidence for human impact on the environment.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00198163
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  • 5
    Electronic Resource
    Electronic Resource
    Long-term human impact as registered in an upland pollen profile from the southern Black Forest, south-western Germany (2000)
    Springer
    Vegetation history and archaeobotany 9 (2000), S. 205-218 
    Details
    ISSN: 1617-6278
    Keywords: Human impact ; Prehistory ; Historical period ; Pollen analysis ; Black Forest
    Source: Springer Online Journal Archives 1860-2000
    Topics: Archaeology , Biology
    Notes: Abstract A detailed,14C-dated, pollen profile from Steerenmoos, a raised bog in the uplands of the southern Black Forest (Schwarzwald) is presented. The Late-glacial and early Holocene vegetation history conforms to the known pattern of forest dynamics for that region. At ca. 6100 cal. B.P.,Abies replaced the mixed oak forest, which is in contrast to adjacent regions whereFagus spread beforeAbies. From the Subboreal onwards,Fagus expanded and slowly largely replacedAbies. The mire developed from a fen to a raised bog. The mountain pine (Pinus mugo ssp.rotundata) on the present-day bog surface is a result of medieval burning. Cereal pollen are first recorded in the Neolithic (7600 cal. B.P.) and there is a closed curve forPlantago Lanceolata — a good indicator of human impact — since the Bronze Age (4000 cal. B.P.). On the basis of the cereal pollen record nine human impact phases (HIP) are described. HIP 1 and 2, which are short, date to ca. 7600 and 6700 cal. B.P., respectively, in a mixed oak forest context and are characterized by declines inCorylus, Tilia, Ulmus and bySalix (but no major deforestation) and peaks in charcoal and loss-on-ignition curves. HIP 3 and 4, which are short and weak, date to ca. 6000 and 5300 cal. B.P., respectively, and occur in the context of anAbies alba forest. The Bronze Age and Iron Age HIPs 5-7 are more intense and of longer duration than the Neolithic phases and result in a decline inAbies and an increase inFagus. The early medieval HIP 8, although rather weak, probably finds expression also in an archaeological artefact, namely a dug-out boat from the near-by Schluchsee. Finally, the late Medieval HIP 9 resulted in a major transformation in the landscape. It is argued that the earlier HIPs are not a reflection of distant events in the lowland valleys of the Rhine, Danube or Neckar but reflect more or less local developments.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01294635
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  • 6
    Electronic Resource
    Electronic Resource
    Human impact as registered in the pollen record: some results from the western Lake Constance region, Southern Germany (1992)
    Springer
    Vegetation history and archaeobotany 1 (1992), S. 101-109 
    Details
    ISSN: 1617-6278
    Keywords: Human impact ; Lake ; Constance ; Lake sediments ; Anthropogenic indicators ; Later Holocene
    Source: Springer Online Journal Archives 1860-2000
    Topics: Archaeology , Biology
    Notes: Abstract Pollen analytical results from a littoral profile taken in Lake Constance compared with pollen profiles from small kettle holes nearby form the basis for conclusions concerning human population density, the economy and environment from the Neolithic period to the Middle Ages. Early Neolithic human impact is implicated in a lime decline and also the expansion of beech. The late Neolithic lakeshore settlements caused a decline of elm, beech and lime and, by shifting cultivation, considerably changed the forest cover. The settlements were abandoned after less than 100 years. There were long periods without distinct human impact in the middle and towards the end of the late Neolithic period. Since at least the Late Bronze Age there has been permanent habitation in the region. Human impact was greatest in the High Medieval period and later, and was also substantial in the late La Tène and Roman periods. Distinct declines in human impact can be observed between the La Tène and Roman periods and in the Migration and Merovingian periods. In these intervals, open land and grazed oak forest were replaced by birch and later on by beech forests. The decreases in human impact are not of the same intensity in all diagrams.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00206090
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  • 7
    Electronic Resource
    Electronic Resource
    Progress in synthesis and application of segmented polymersDedicated to Prof. Dr. H. Sinn on the occasion of his 65th birthday (1994)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 223 (1994), S. 47-60 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Maßgeschneiderte segmentierte Polymere spielen eine Schlüsselrolle bei der Entwicklung von neuen polymeren Materialien. In Abhängigkeit von den molekularen Architekturen der segmentierten Polymeren kann die Ausbildung von Polymermorphologien und von Eigenschaftssynergien gesteuertwerden. An ausgewählten Beispielen werden grundlegende Konzepte und neuere Entwicklungen vorgestellt. Segmentierte Silikon-Flüssigkautschuke, wo unverträgliche Silikonsegmente von zwei mischbaren Oligo(caprolacton)-Segmenten flankiert werden, sind wirkungsvolle Zähmodifikatoren für Epoxidharze. In nanophasenseparierten IPNs auf Basis dieser Silikon-modifizierter Epoxidharze kann die Schlagzähigkeit ohne Verlust der Dimensionsstabilität erhöht werden. Kompatibilisierte Blends aus segmentierten phenolischen Polyurethan- und epoxidfunktionellen Nitril-Flüssigkautschuken bilden diskrete Blend-Mikrophasen, die in Epoxidprepregs dispergiert sind und strukturelles Verkleben von Aluminium in Faser-Metall Laminaten ermöglichen. Reaktive Blendtechnologien werden entwickelt, um während der Polymerverarbeitung, z.B. von Polypropylen/Polyamid 6 Blends, in-situ Phasenvermittler herzustellen. Durch Einbau von definierten Oligo(tetrafluoroethene) Segmenten in Kodensationspolymere werden neben thermischen und mechanischen Eigenschaften auch Oberflächenspannungen und Gasdurchlässigkeiten variiert.
    Notes: Tailor-made segmented polymers play a key role in the development of novel polymeric materials exhibiting unsual bulk and surface properties. As a function of molecular architectures of segmented polymers, it is possible to control polymer morphologies and to achieve property synergisms. Selected examples are presented to illustrate basic concepts and recent developments. Segmented reactive liquid rubbers, containing an immiscible silicone segment flanked by two miscible oligo(caprolactone) segments, are efficient epoxy toughening agents. In such nano-phase-separated silicone-modified IPNs impact strength is improved without sacrificing dimensional stability. Compatibilized blends of segmented phenolic polyurethane and nitrile liquid rubbers produce rubber blend microphases dispersed in epoxy prepregs which are used to bond aluminum sheets in structural laminates. Reactive blending technologies are developed to produce segmented polymers as blend compatibilizers during melt processing, e.g., of polypropylene/polyamide 6 blends. Incorporation of oligo(tetrafluoroethene) segments into various condensation polymers modifies thermal and mechanical properties as well as surface tension and gas permeabilities.
    Additional Material: 13 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1994.052230104
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  • 8
    Electronic Resource
    Electronic Resource
    Organometallphosphin-substituierte Übergangsmetall-Komplexe, X. Organometallphosphin-tetracarbonyl-eisen-Komplexe (1970)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 103 (1970), S. 2350-2355 
    Details
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Organometalphosphine Substituted Transition Metal Complexes, X. (Organometalphosphine)tetracarbonyliron ComplexesPentacarbonyliron reacts on u. v. irradiation with tri(tert-butyl)-, tris(trimethylsilyl)-, tris(tri-methylgermyl)-, and tris(trimethylstannyl)phosphine with displacement of one CO-ligand to give the corresponding tris[(triorganoelement-IVa)phosphine]tetracarbonyliron complexes. The same compounds can also be synthesized by elimination of pentacarbonyliron from enneacarbonyldiiron in the presence of the tris(triorganoelement-IVa)phosphines. The i. r., 1H n. m. r., and 31P n. m. r. spectroscopic data of the complexes are reported and discussed.
    Notes: Pentacarbonyleisen reagiert bei UV-Bestrahlung mit Tri(tert.-butyl)-, Tris(trimethylsilyl)-, Tris(trimethylgermyl)- bzw. Tris(trimethylstannyl)-phosphin unter Abspaltung eines CO-Liganden und Bildung entsprechender [Tris(triorganoelement-IVa)-phosphin]-tetracarbonyl-eisen-Komplexe. Dieselben Verbindungen entstehen auch unter Abspaltung von Pentacarbonyleisen aus Enneacarbonyldieisen und den genannten Tris(triorganoelement-IVa)-phosphinen. Die IR-, 1H-NMR- und 31P-NMR-spektroskopischen Daten der Komplexe werden mitgeteilt und diskutiert.
    Additional Material: 4 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19701030806
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  • 9
    Electronic Resource
    Electronic Resource
    Organometallphosphin-substituierte Übergangsmetallkomplexe, XIX. Tetracarbonyl(organometallphosphin)eisen-Komplexe (1975)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 108 (1975), S. 2487-2499 
    Details
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Organometalphosphine-substituted Transition Metal Complexes, XIX. Tetracarbonyl(organometalphosphine)iron ComplexesPentacarbonyliron reacts under u. v. irradiation with tri(tert-butyl)phosphine (1), di(tert-butyl)-trimethylsilyl-, -germyl- and -stannylphosphine (2-4), tert-butylbis(trimethylsilyl-, -germyl- and -stannyl)phosphine (5-7) as well as with tris(trimethylsilyl-, -germyl- and -stannyl)phosphine (8-10) with displacement of one CO-ligand and formation of the corresponding tetracarbonyl-(organometalphosphine)iron complexes 1a - 10a. The i. r., Raman, 1H n. m. r., and 31P n. m. r. spectra of the complexes are discussed.
    Notes: Pentacarbonyleisen reagiert bei UV-Bestrahlung mit Tri(tert-butyl)phosphin (1), Di(tert-butyl)-trimethylsilyl-, -germyl- bzw. -stannylphosphin (2-4), tert-Butybis(trimethylsilyl-, -germyl- bzw. -stannyl)phosphin (5-7) sowie mit Tris(trimethylsilyl-, -germyl- bzw. -stannyl)phosphin (8-10) unter Abspaltung eines CO-Liganden und Bildung entsprechender Tetracarbonyl(organometallphosphin)eisen(0)-Komplexe 1a - 10a. Die Infrarot-, Raman-, 1H-NMR- und 31P-NMR-Spektren werden diskutiert.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19751080802
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  • 10
    Electronic Resource
    Electronic Resource
    Notiz zur Photolyse von Bicyclo[6.2.0]deca-2,4,6-trien (1977)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 110 (1977), S. 2394-2397 
    Details
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19771100638
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