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  • Inorganic Chemistry  (27)
  • Computational Chemistry and Molecular Modeling  (18)
  • 42.75
  • 1995-1999  (19)
  • 1980-1984  (21)
  • 1960-1964  (6)
  • 1
    Electronic Resource
    Electronic Resource
    Active-site α-helix in papain and the stability of the ion pair RS- ··· ImH+. Ab initio molecular orbital study (1980)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 17 (1980), S. 651-671 
    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: Ab initio MO calculations, using both minimal (STO-3G) and extended (Roos-Siegbahn) basis sets are reported for the systems methanethiol-imidazole, methanethiol-imidazole-formaldehyde, and methanethiol-imidazole-formamide, which, together with a point-change representation of a long α-helix, form models for the active site of papain. It is shown that the large electric field exerted by the helix in the active-site region is responsible for the presence of the essential residues Cys 25 and His 159 in the form of an ion pair RS- ··· ImH+, which is crucial for a recently proposed mechanism for the catalytic action of the enzyme. Also, an explanation is given for the anomalies in measured pK values for these residues. Detailed studies on the (sub)systems show that minimal basis sets lack the flexibility necessary for describing the type of proton transfer involved. We conclude that α-helices are essential parts of enzymes and that they play a significant role in the catalytic process.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560170407
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  • 2
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    De edelherthorzel Cephenemyia auribarbis gekweekt (Diptera: Oestridae) (1999)
    In:  Nederlandse Faunistische Mededelingen (01692453) vol.9 (1999) p.109
    Details
    Publication Date: 2007-01-10
    Description: The rearing of the botfly Cephenemyia auribarbis (Diptera: Oestridae) After several failures we finally succeeded in rearing botflies Cephenemyia from third-instar larvae. From a red deer shot at 13 March 1998 about one hundred larvae of Cephenemyia auribarbis (Meigen, 1824) were collected. Ten individuals reached the pupal stage. After 22 days, one fullgrown male died in the pupa, and two males emerged and lived for 17 and 18 days respectively. This is one of the few recorded succesful attempts to rear botflies.
    Keywords: Insecta ; Diptera ; Oestridae ; Cephenemyia auribarbis ; Nederland ; Verspreiding ; 42.75
    Repository Name: National Museum of Natural History, Netherlands
    Type: Article / Letter to the editor
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  • 3
    Electronic Resource
    Electronic Resource
    Utopia dielectrica (1995)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 56 (1995), S. 523-531 
    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 dielectric constant of a material is a macroscopic property that measures the reduction of the electrostatic forces between charged plates separated by the material, compared to a vacuum as intermediate material. It is next encountered as a scaling parameter in Coulomb's law for interacting charges, not only in the force, but also in the energy. In deriving the theory for dielectrics, the macroscopic nature is essential: Only then is the basic assumption that the dielectric material is homogeneous and isotropic a valid one. The appearance of the dielectric constant as a simple scaling factor in Coulomb's law has tempted many computational chemists to forget about the macroscopic nature of the dielectric and to apply the screened Coulomb's law between charges, supposedly in a low-dielectric medium such as proteins, in microscopic force fields. Optimization of force fields even led to distance-dependent “dielectric constants.” Another use of the dielectric constant appears in the dielectric continuum reaction field approaches for the computations of solvation energies and solvent effects. The solute is embedded in a cavity surrounded by the dielectric. Specific interactions between solvent molecules and solute are thus neglected. The cavity size and dielectric constants of interior and exterior are optimized for the model. The aim of this article is to show, by means of calculations on interacting point charges embedded in cavities surrounded by dielectrics and microscopic models of “low-dielectric” materials by explicit polarizabilities, that as far as the dielectric “constant” is concerned anything can happen, depending on the nature of the charges, the distance to the cavity boundary, the spatial arrangement of charges, and polarizabilities. Thus, a warning is issued to injudicious use of dielectric models in microscopic calculations. © 1995 John Wiley & Sons, Inc.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560560855
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  • 4
    Electronic Resource
    Electronic Resource
    Solvatochromism of the π* ← n transition of acetone by combined quantum mechanical - classical mechanical calculations (1996)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 57 (1996), S. 1067-1076 
    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 solvent shift of the π* ← n transition of acetone in water, acetonitrile, and tetrachloromethane was calculated in a combined quantum mechanical - classical mechanical approach, using both dielectric continuum and explicit, polarizable molecular solvent models. The explicit modeling of solvent polarizability allows for a separate analysis of electrostatic, induction, and dispersion contributions to the shifts. The calculations confirm the qualitative theories about the mechanisms behind the blue shift in polar solvents and the red shift in nonpolar solvents, the solvation of the ground state due to electrostatic interactions being preferential in the former, and favorable dispersion interaction with the excited state, in the latter case. Good quantitative agreement for the solvent shift between experiment (+1,700, +400, and -350 cm-1 in water, acetonitrile, and tetrachloromethane, respectively) and the explicit solvent model (+1,821, +922, and -381 cm-1) was reached through a modest Monte Carlo sampling of the solvent degrees of freedom. A consistent treatment of the solvent could only be realized in the molecular solvent model. The dielectric-only model needs reparameterization for each solvent. © 1996 John Wiley & Sons, Inc.
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  • 5
    Electronic Resource
    Electronic Resource
    Calculations of molecules, clusters, and solids with a simplified LCAO-DFT-LDA scheme (1996)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 58 (1996), S. 185-192 
    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: A simplified LCAO-DFT-LDA scheme for calculations of structure and electronic structure of large molecules, clusters, and solids is presented. Forces on the atoms are calculated in a semiempirical way considering the electronic states. The small computational effort of this treatment allows one to perform molecular dynamics (MD) simulations of molecules and clusters up to a few hundred atoms as well as corresponding simulations of condensed systems within the Born-Oppenheimer approximation. The accuracy of the method is illustrated by the results of calculations for a series of small molecules and clusters. © 1996 John Wiley & Sons, Inc.
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  • 6
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    Electronic Resource
    Beiträge zur Chemie des Phosphors. 115. Synthese und Eigenschaften des Tetraphospha-silaspiro-[2.2]pentans (PBut)2Si(PBut)2Professor Rudolf Hoppe zum 60. Geburtstage gewidmet (1982)
    Weinheim : Wiley-Blackwell
    Zeitschrift für anorganische Chemie 491 (1982), S. 27-33 
    Details
    ISSN: 0044-2313
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Contributions to the Chemistry of Phosphorus. 115. Synthesis and Properties of the Tetraphospha-silaspiro[2.2] pentane (PBut)2Si(PBut)2The first spirocyclic phosphorus-silicon three-membered ring compound, 1,2,4,5-tetra-tert-butyl-1,2,4,5-tetraphospha-3-silaspiro[2.2]pentane, (PBut)2Si(PBut)2 (1), has been synthesized by cyclocondensation of K(But)P—P(But)K with silicon tetrachloride in the molar ratio of 2:0.9. It was characterized by elemental analysis, cryoscopic molecular weight determination and its mass, magnetic resonance and vibrational spectra. 1 is formed as a mixture of two diastereomers 1a and 1b. These differ in the relative arrangement of the trans-oriented organyl substituents at the two three-membered rings; both isomers could be obtained in a pure state. The sterically less favoured isomer 1b rearranges into the comparatively more stable isomer 1a.
    Notes: Die erste spirocyclische Phosphor-Silicium-Dreiringverbindung, das 1,2,4,5-Tetra-tert-butyl-1,2,4,5-tetraphospha-3-silaspiro[2.2]pentan, (PBut)2Si(PBut)2 (1), wurde durch Cyclokondensation von K(But)P—P(But)K mit Siliciumtetrachlorid im Molverhältnis 2:0,9 synthetisiert. Die Charakterisierung erfolgte durch Elementaranalyse, kryoskopische Molmasse-Bestimmung, Massen-, Kernresonanz- und Molekülschwingungsspektren. 1 entsteht als Gemisch von zwei Diastereomeren 1a und 1b, die sich in der Anordnung der jeweils trans-ständigen Organylgruppen beider Dreiringe zueinander unterscheiden; beide Isomere konnten rein erhalten werden. Das sterisch ungünstigere Isomer 1 b lagert sich in das vergleichsweise beständigere Isomer 1 a um.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/zaac.19824910104
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  • 7
    Electronic Resource
    Electronic Resource
    Beiträge zum thermischen Verhalten von Sulfaten. VI. Zum chemischen Transport von CuSO4, Cu2OSO4 und CuO (1983)
    Weinheim : Wiley-Blackwell
    Zeitschrift für anorganische Chemie 498 (1983), S. 153-160 
    Details
    ISSN: 0044-2313
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Contributions on the Thermal Behaviour of Sulfates. VI. On the Chemical Transport of CuSO4, Cu2OSO4, and CuOA powder of anhydrous CuSO4 can be prepared by heating CuSO4 · 5 H2O in air or in an argon atmosphere. In the same way it is possible to get a powder of Cu2OSO4. But up to now, it was difficult to get crystals of CuSO4 and there was no method known to synthesize crystals of Cu2OSO4. Investigations concerning chemical transport reactions of anhydrous heavy metal sulfates showed, that it is possible to get well formed crystals of CuSO4 and Cu2OSO4 by deposition from a vapour phase. As transport agents for CuSO4, Cl2 and HgCl2 are especially suitable. Less appropriate are HCl, NH4Cl, and I2.The chemical vapor deposition of Cu2OSO4 proceeds well with HgCl2. In course of these investigations we recognized, that for CuO in addition to the well approved transport agents also Cl2, HgCl2 or I2 (NH4Cl less suitable) can successfully be used.
    Notes: Wasserfreies CuSO4 ist in Pulverform durch thermischen Abbau der Hydrate leicht zugänglich, pulverförmiges Cu2OSO4 läßt sich dementsprechend aus CuSO4 darstellen. Kristalle waren dagegen bisher von CuSO4 nur sehr schwierig und von Cu2OSO4 noch nicht synthetisch zu gewinnen. Wie sich im Rahmen einer Untersuchung zum chemischen Transport wasserfreier Schwermetallsulfate zeigte, sind gut ausgebildete Kristalle von CuSO4 und Cu2OSO4 durch Abscheidung aus der Gasphase zugänglich. Als Transportmittel für CuSO4 sind besonders Cl2 und HgCl2 geeignet, weniger brauchbar sind HCl, NH4Cl oder I2. Das Oxidsulfat ist mit HgCl2 und NH4Cl, weniger gut mit I2 zu transportieren. Dabei fanden wir, daß für CuO außer den dafür bereits erprobten Transportmitteln auch Cl2, HgCl2 und I2 (NH4Cl weniger gut) verwendbar sind.
    Additional Material: 2 Ill.
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    URL: http://dx.doi.org/10.1002/zaac.19834980320
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  • 8
    Electronic Resource
    Electronic Resource
    Beiträge zur Strukturchemie phosphorhaltiger Ketten und Ringe. 11. Die Kristall- und Molekülstrukturen der beiden Konfigurationisomeren des Tetraphospha-silaspiro[2.2]pentans (PBut)2Si(PBut)2Die Ergebnisse dieser Untersuchung sind am 9. 8. 1983 auf dem “Eighth European Crystallographic Meeting” (ECM 8) in Lüttich kurz mitgeteilt worden [2]. (1984)
    Weinheim : Wiley-Blackwell
    Zeitschrift für anorganische Chemie 515 (1984), S. 7-18 
    Details
    ISSN: 0044-2313
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Structural Chemistry of Phosphorus Containing Chains and Rings. 11. Crystal and Molecular Structures of the Two Stereoisomers of Tetraphospha-silaspiro[2.2]pentane (PBut)2Si(PBut)2The spirocyclic compound 1,2,4,5-tetra-tert-butyl-1,2,4,5-tetraphospha-3-silaspiro[2.2]pentane exists in tow diastereomers of point symmetry 4 and 2. The isomer with symmetry 4 even in the solid crystallizes tetragonally in I41/a with a = 1247.0, c = 1505.5 pm and Z = 4. The isomer of fairly exact symmetry 2 crystallizes triclinically in P1 with a = 612.8, b = 996.3, c = 1017.2 pm, α = 75.63, β = 72.38, γ = 88.71° and Z = 1. In this disordered structure the surroundings of Si is slightly distorted due to the influence of the substituents. The (average) bond lengths are (4, 2): d(Si—P) = 220.09(9), 221.5(5); d(P—P) = 225.5(2), 224.2(5); d(P—C) = 189.4(3), 190(2); d(C—C) = 151.4(4), 152(3) pm. The geometry of the substituents in both isomers is quite normal.
    Notes: Die Spiroverbindung 1,2,4,5-Tetra-tert-butyl-1,2,4,5-tetraphospha-3-silaspiro[2.2]pentan liegt in zwei Diastereomeren der Punktsymmetrie 4 und 2 vor. Das Isomer der auch im Festkörper exakten Symmetrie 4 kristallisiert tetragonal in der Raumgruppe I41/a mit a = 1247,0, c = 1505,5 pm und Z = 4. Das sterisch weniger günstige Isomer der im Festkörper nicht streng erfüllten Symmetrie 2 kristallisiert triklin in der Raumgruppe P1 mit a = 612,8, b = 996,3, c = 1017,2 pm, α = 75.63, β = 72,38, γ = 88,71° und Z = 1. In dieser nur fehlgeordnet beschreibbaren Struktur wird die Umgebung des Si durch Substituenteneinflüsse etwas verzerrt. Die (mittleren) Bindungslängen betragen (4, 2): d(Si—P) = 220,09(9), 221,5(5); d(P—P) = 225,5(2), 224,2(5); d(P—C) = 189,4(3), 190(2); d(C—C) = 151,4(4), 152(3) pm. Die Geometrie der Substituenten ist in beiden Isomeren normal.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/zaac.19845150802
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  • 9
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    Electronic Resource
    Zur Kenntnis des Sulfuryl-Disulfamids, O2S(NH—SO2—NH2)2 (1962)
    Weinheim : Wiley-Blackwell
    Zeitschrift für anorganische Chemie 318 (1962), S. 190-197 
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    ISSN: 0044-2313
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: (H2N-SO2-NH)Na and SO2Cl2 react in cold anhydrous acetonitrile yielding mainly O2S(NH-SO2-NH2)2 (I) and, to a small extent, (O2S-NH)4 (II). Both strongly hygroscopic compounds could not yet be obtained in the pure state. They are readily soluble in water, ethanol, and ether, though the solubility of II in ether is limited.The preparations and properties of the K-, Ba-, and Ag-salt of I are described. Methylation of I by means of diazomethane yields the very stable O2S[N(CH3)-SO2-N(CH3)2]2; its molecular weight confirms the formula given.By interaction of the starting compounds in boiling acetonitrile, the yield of (O2S-NH)4 increases; its Ba- and Ag-salt are characterized.
    Notes: Sulfamid-Natrium und Sulfurylchlorid reagieren in kaltem Acetonitril bei Wasserausschluß bevorzugt nach 2 H2N-SO2-NH-Na + Cl2SO2 → O2S(NH-SO2-NH2)2 + 2 NaCl. Daneben vollzieht sich in geringen Umfange, besser in der Siedehitze 2 H2N-SO2-NH-Na + 2 Cl2SO2 → (O2S-NH)4 + 2 NaCl + 2 HCl. Beide stark hygroskopischen Verbindungen wurden noch nicht rein erhalten, die 7gliedrige Verbindung ist neben anderen Solventien gut in Wasser, Äthanol und Äther, das wasserfreie (O2S-NH)4 gut in Wasser und Alkohol, weniger gut in Äther löslich.Das reine in Wasser mit neutraler Reaktion gut lösliche K-Salz, O2S(NK-SO2-NH2)2, liefert beim trockenen Erhitzen Trisulfimid, (O2S-NK)3, auch beim Erhitzen mit KOH, wobei aber NH3 abgespalten wird. Weiter wurde das in Wasser lösliche O2S(N-SO2-NH2)2 · Ba, 2 H2O und das darin unlösliche O2S(NAg-SO2-NH2)2 erzeugt. Bei tagelanger Einwirkung von ätherischer Diazomethan-Lösung auf eine ebensolche von rohem Sulfuryl-Disulfamid läßt sich das sehr beständige, bei 161° schmelzende O2S[N(CH3)-SO2-N(CH3)2]2 mit dem der Formel entsprechenden Molekulargewicht isolieren.Läßt man die O2SCl2-Umsetzung in siedendem Acetonitril sich vollziehen, so entsteht neben Trisulfimid mehr Tetrasulfimid. Das in kaltem Wasser schwerlösliche Ba2(NSO2)4, 2 H2O ließ sich gewinnen, ebenso das unlösliche (AgNSO2)4, dessen Debyeogramm mit dem in heißem Wasser löslichen (AgNSC2)3 aufgenommen und verglichen wurde.
    Additional Material: 1 Tab.
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    URL: http://dx.doi.org/10.1002/zaac.19623180308
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  • 10
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    Einfache Darstellung von Sulfamid-Monosulfonaten H2N—SO2—N(Me)—SO3Me und Na-Sulfamid-Monosulfosäure-Äthylester H2N—SO2—N(Na)—SO2—OC2H5 (1963)
    Weinheim : Wiley-Blackwell
    Zeitschrift für anorganische Chemie 324 (1963), S. 297-303 
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    ISSN: 0044-2313
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: H2N—SO2—NH—Na reacts with Cl—SO3H or Cl/SO2—OC2H5 in boiling anhydrous nitromethane or acetonitrile yielding about 70—80% H2N—SO2—N(Na)—SO3Na(I).By means of I, the unknown (H2N—SO2—N—SO3)Ba, 2 H2O and (H2N—SO2—N—SO3)3- [Co(NH3)6]2 → 2H2O are obtained and their properties described.By interaction of H2N—SO2—NH—Na with Cl—SO2—OC2H5 at room temperature, 65% of H2N—SO2—N(Na)—SO2—OC2H5 were isolated. The hydrolysis with water or hydrochloric acid yields O2S(NH2)2 and C2H5O—SO3Na, that with ethanolic NaOH, however, I.
    Notes: Überschüssiges Na-Sulfamid reagiert mit Chloroschwefelsäure sowie deren Äthylester in siedendem Nitromethan oder Acetonitril bei völligem Feuchtigkeitsausschluß nach bzw. zu 70—80% unter Bildung von Na-Sulfamid-Monosulfonat.Das reine, mit stark alkalischer Reaktion in Wasser leichtlösliche Na-Salz H2N—SO2—N(Na)—SO3Na bildet ein Monohydrat. Es wurde zu den noch unbekannten Verbindungen (H2N—SO2—N—SO3)Ba, 2 H2O und (H2N—SO2—N—SO3)3 [Co(NH3)6]2, 2 H2O umgesetzt.Bei der Reaktion von Sulfamid-Natrium mit Cl—SO2—OC2H5 in Acetonitril bei Raumtemperatur entsteht mit 65% Ausbeute das Na-Salz des Sulfamid-Monosulfosäure-Äthylesters: das sich mit alkoholischer KOH zu H2N—SO2—N(Na)—SO3Na, hingegen mit Wasser oder 2 n HCl zu Sulfamid und Na-Äthylsulfat verseifen läßt.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/zaac.19633240510
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