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  • 1
    ISSN: 1399-0047
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: Rhodobacter capsulatus strain St Louis cytochrome c′ (RCCP-SL) has been crystallized and the structure solved by molecular replacement. It was refined at 2.1 Å resolution to an R value of 18.4%, and compared with Rhodobacter capsulatus strain M110 cytochrome c′ (RCCP-M110). Although these two proteins are very similar in sequence and structure, the intermolecular interaction is largely different. In RCCP-M110, the molecules dimerize through interaction of helix B to form an antiparallel arrangement. When crystallized in the presence of Zn ions, molecules of RCCP-SL were found to be arranged as linear polymers connected by the bridging Zn ions. The changes in conformation of the side chains induced by binding of the Zn ions, by the substitution of Glu90 for Asp90, and by the different arrangement of the molecules, are discussed in detail.
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  • 2
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    ISSN: 0935-6304
    Keywords: Gas chromatography ; Capillary column, glass ; Interface, home-made ; Headspace analysis ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 3 Ill.
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  • 3
    ISSN: 1399-0047
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: A new crystal form of diheme cytochrome c′ from Rhodobacter capsulatus has been obtained and preliminary crystallographic experiments have been performed. The crystals belong to the space group P21212 with unit-cell dimensions of a = 47.82, b = 72.59, c = 34.32 Å. The assumption that an asymmetric unit of the crystal contains one half of the homodimer molecule indicates that the monomers in the dimeric molecule may be related by a crystallographic twofold axis. Crystals diffract up to 1.7 Å resolution using the X-ray beam from synchrotron radiation, and 11 127 unique structure factors were obtained with an Rmerge of 7.1% from 52 922 indexed reflections. Structure analysis by means of molecular-replacement methods is now underway.
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  • 4
    ISSN: 1398-9995
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Background:  Worm infestations may play a role in preventing allergies. There is a lack of epidemiological information from Western countries on the association between worm infestation and eczema.Objective:  To investigate the association between worm infestation and eczema in a proper temporal sequence and under consideration of allergic sensitization.Methods:  Two surveys were performed in East German school children. Questionnaire data included the history of eczema and worm infestation and their time of onset. Specific IgE antibodies to five common aeroallergens were measured and used to define nonatopic and atopic eczema. Logistic regression analyses were performed to control for relevant confounders (age, sex, parental school education and history of allergies). In order to confirm the findings a corresponding conditional regression analysis was applied on cases and controls matched by age and sex.Results:  A total of 4169 children participated (response 75 and 76%) who were, on average, 9.2 years old (47% girls). Overall 17.0% reported a prior worm infestation (Ascaris 44%, Oxyuris 33%) and 18.1% had a history of eczema. Eczema occurred significantly less frequent in children who had a worm infestation (prior to the onset of eczema) compared with children without such a history (8.1%vs 16.5%, ORadj: 0.45, 95% CI: 0.33–0.60). The finding was confirmed by the corresponding matched case–control analysis (ORadj: 0.57, 95% CI: 0.41–0.79). Atopic eczema was affected more by a prior worm infestation (ORadj: 0.31, 95% CI: 0.18–0.56) than the nonatopic eczema (ORadj: 0.58, 95% CI: 0.40–0.84). A total of 29.1% exhibited specific IgE antibodies to at least one aeroallergen. Sensitized children gave significantly less frequent a history of worm infestation (14.2%vs 18.3%, ORadj: 0.74, 95% CI: 0.60–0.92). Stratified analysis revealed that this effect most pronounced for a sensitization to house dust mite.Conclusions:  A worm infestation is associated with a reduced frequency of subsequent eczema, especially the atopic type. Furthermore allergic sensitization, especially to house dust mite, and worm infestation are negatively associated. The data support the concept that a lack of immune-stimulation by parasitic infections contributes to the development of allergies.
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  • 5
    ISSN: 0730-2312
    Keywords: rat protein kinase C ; recombinant baculovirus ; antisera ; phorbol ester ; isoenzymes ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Expression of rat protein kinase C-δ (PKC-δ ) and PKC-ξ in insect cells using recombinant baculovirus resulted in the production of proteins with a molecular size of approximately 76 kD and 78 kD, respectively, as determined by immunoblotting with subtype-specific antisera. Although the PKC-ξ cDNA encoded for 592 amino acids, a 76 kD protein was also generated by in vitro transcription/translation. Extracts of cells expressing PKC-δ were able to bind phorbol ester to levels comparable to extracts of cells expressing PKC-α. No phorbol ester binding was, however, detected in insect cell extracts expressing PKC-ξ. However, similar levels of protein kinase activity were detected in lysates of cells expressing PKC-δ or PKC-ξ when protamine sulfate was used as exogenous substrate. Compared to protamine sulfate, both, myelin basic protein (MBP) or histone, were poor substrates for PKC-δ and PKC-ξ. In contrast to PKC-ξ, the PKC-δ enzyme activity phosphorylated MBP or histone in a phosphatidylserine-(PS)/diacylglycerol(DG)-dependent manner, albeit not to the same extent as PKC-α. Lack of stimulation of the enzyme activity of PKC-ξ by PS/DG, was confirmed by endogenous phosphorylation of insect cell proteins by PKC-ξ, whereas several insect cell proteins were phosphorylated by PKC-δ in a PS/DG-dependent manner, including a protein of 78 kD.Our data demonstrate that the 76 kD PKC-ξ, in contrast to PKC-δ, is unable to bind phorbol esters and displays a protein kinase activity that is independent of PS of PS/DG. In addition, staurosporine was about 2-4 order of magnitudes less effective in inhibiting the protein kinase activities of PKC-δ and PKC-δ when compared to PKC-ξ.
    Additional Material: 7 Ill.
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  • 6
    ISSN: 0044-2313
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Structure of TetraphenyldisiloxaneTetraphenyldisiloxane 1 crystallizes at 298 K monoclinically (P21/n; a = 1407.6; b = 610.7; c = 1262.7 pm; β = 95.87° Z = 2) and undergoes a second order phase transition at 200 K, in an almost unchanged structure of triclinic symmetry. At 298 K the molecules are already bent (Si—O—Si = 160°) with static or dynamical disorder of the bridging atom. Both Si—O distances are different (156 or 169 pm), because the shift of the bridging O atom is not perpendicular to the Si—to—Si vector. The reason for this remarkable behavior is not yet clear. According to the vibrational spectra, the Si—O—Si bridge is bent in the crystal but, in CCl4 solution a dynamical oscillation through the linear configuration may occur.
    Notes: Tetraphenyldisiloxan 1 kristallisiert bei 298 K monoklin (P21/n; a = 1407,6 pm; b = 610,7 pm; c = 1262,7 pm; β = 95,87° Z = 2) und durchläuft bei 200 K einen Phasenübergang 2. Ordnung in eine kaum veränderte Struktur trikliner Symmetrie. Bereits bei 298 K liegen in der Struktur gewinkelte Moleküle (Si—O—Si = 160°) mit statischer oder dynamischer Fehlordnung des Brückenatoms vor. Die beiden Abstände Si—O sind verschieden (156 bzw. 169 pm), weil die Auslenkung des Brückenatoms aus der zentralen Lage nicht senkrecht zum Vektor Si—Si erfolgt. Der Grund für dieses merkwürdige Verhalten ist unklar. Die Schwingungsspektren beweisen für den kristallinen Zustand ebenfalls die gewinkelte Struktur, während in CCl4-Lösungen ein dynamisches Durchschwingen durch die gestreckte Konfiguration wahrscheinlich ist.
    Additional Material: 6 Ill.
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  • 7
    ISSN: 0044-2313
    Keywords: Polyphosphides ; Zintl-phases M3X11 (M = Na, K, Rb, Cs; X = P, As) ; P113-, As113- cage anion ; preparation ; vibrational spectra ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Chemistry and Structural Chemistry of Phosphides and Polyphosphides. 53. Preparation, Properties, and Vibrational Spectra of the Cage Anions P113- and As113-The Zintl-phases M3X11 (M = Na, K, Rb, Cs; X = P, As) are prepared from the elements or from M3X7 and X. The compounds undergo a first-order phase transition from the crystalline to the plastically crystalline state. Unit cell and space group of both modifications and the transition temperature Tc are determined. The vibrational spectra of the crystalline compounds and the Raman spectrum of the P113- anion in en-solution as well are measured. The assignment of the frequencies is given, based on the 32-D3 symmetry of the X113- cage anion. Normal coordinate analysis is carried out in terms of Cartesian coordinates to avoid the problem of redundancies in using internal coordinates. The force constants [mdyn Å-1] obtained for the characteristic bonds r, s, and t are: fppr = 1.34, fpps = 1.20, fppt = 1.08; fAsAsr = 1.1, fAsAss = 0.91. Normal vibrations and the potential energy distribution (PED) are discussed.
    Notes: Die Zintl-Phasen M3X11 (M = Na, K, Rb, Cs; X = P, As) werden aus den Elementen oder aus M3X7 und X synthetisiert. Die Verbindungen durchlaufen einen Phasenübergang 1. Ordnung vom kristallinen zum plastisch-kristallinen Zustand. Elementarzelle und Raumgruppe beider Modifikationen sowie Übergangstemperaturen Tc wurden bestimmt. Die Schwingungsspektren der kristallinen Verbindungen sowie das Raman-Spektrum des Anions P113- in en-Lösung wurden gemessen. Die Zuordnung der Schwingungsfrequenzen gelingt auf der Basis der Symmetrie 32-D3 der Käfiganionen X113-. Die Normalkoordinatenanalyse erfolgte in kartesischen Koordinaten, wodurch das in inneren Koordinaten auftretende Redundanzproblem vermieden wird. Auf diesem Wege erhaltene Kraftkonstanten [mdyn Å-1] der charakteristischen Bindungen r, s und t sind: fppr = 1, 34, fpps = 1, 20, fppt = 1, 08; fAsAsr = 1, 1, fAsAss = 0, 96, fAsAst = 0, 91. Die Normalschwingungen und die Verteilung der potentiellen Energie (PED) werden diskutiert.
    Additional Material: 4 Ill.
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  • 8
    ISSN: 0044-2313
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Chemistry and Structural Chemistry of Phosphides and Polyphosphides. 46. Tetrarubidiumhexaphosphide and Tetracesiumhexaphosphide. Preparation, Structure, and Properties of Rb4P6 and Cs4P6Tetrarubidium and tetracesiumhexaphosphide have been prepared quantitatively by reaction of the elements in sealed Nb ampoules at 870 K and 920 K, respectively. Both compounds are black semiconductors (EG ≍ 1.3 - 1.6 eV) and show metallic lustre. Their crystal structures are orthorhombic defect variants M4P6□2 of the hexagonal AlB2 type structure. Characteristic building units are planar isometric P6 rings with bond lengths d(P—P) = 215 and 214 pm, respectively, representing an aromatic 10° system with one double bond, delocalized about six bonds. Thermal decomposition in Ta crucibles yields quantitatively M3P7. The compounds M4P6 disproportionate in ethylendiamine into M3P7, and M3P, as revealed by 31P n.m.r. spectra. In the down field region a singulett (Δ(α-K4P6) = 331; Δ(Rb4P6) = 337; Δ(Cs4P6) = 348) is observed, which can be ascribed to the valence tautomeric hexaphosphene (4). The internal vibrations of the P6 ring have been observed by i.r. and raman-spectra. For Cs4P6 the fundamental vibrations are v(A1g)=356 cm-1 and v(E2g)=507 and 202 cm-1, respectively, and show the same sequence as for benzen. Semiempirical LCAO-MO calculations show, that in the series P6n- with n=2,4, 6 the anion P62- is the most stable one but the unit M2P6-1 becomes more stable as the other isomers by forming the M2[μ-(η6-P6)] complex. Among the isomers of P64- the hexagonal planar 10π system is about 7 eV more stable than the isomeric bicyclo-tetraanion.
    Notes: Tetrarubidium-und Tetracäsiumhexaphosphid werden beim quantitativen Umsatz der Elemente bei 870 K bzw. 920 K in Nb-Ampullen erhalten. Beide Verbindungen sind schwarze Halbleiter (EG ≈ 1,3 - 1,6 eV), die Kristalle zeigen metallischen Glanz. Die Strukturen sind orthorhombische Defektvarianten M4P6□2 der hexagonalen AlB2-Struktur mit planaren isometrischen P6-Ringen als charakteristische Baueinheiten. Die Bindungslänge d(P—P) = 215 bzw. 214 pm entspricht einem aromatischen 10° System mit einer über die sechs Bindungen delokalisierten Doppelbindung. Beim thermischen Abbau entsteht quantitativ M3P7. In Lösungen von Ethylendiamin disproportionieren die Verbindungen M4P6 in M3P7 und M3P. Intermediär treten im Tieffeldbereich von 31P-NMR-Spektren jeweils Singulett-Signale auf (Δ(α-K4P6) = 331; Δ(Rb4P6) = 337; Δ(Cs4P6) = 348), die dem valenztautomeren Hexaphosphen(4) zugeschrieben werden. Die inneren Schwingungen der P6-Ringe wurden aus IR-und Raman-Spektren ermittelt. Für Cs4P6 liegen die Fundamentalschwingungen bei n̈(A1g) = 356 cm-1, n̈(E2g) = 507 bzw. 202 cm-1. Diese Abfolge entspricht derjenigen von Benzol. Mit semiempirischen LCAO-MO Rechnungen wird gezeigt, daß in der Reihe P6n- mit n = 2, 4, 6 zwar das Anion P62- das stabilste ist, daß jedoch mit der Bildung eines M2[m̈-(η6-P6)]-Komplexes die Einheit M2P62- wesentlich stärker stabilisiert wird als die übrigen Isomeren. Unter den Isomeren P64- ist das hexagonal-planare 10°System um 7 eV stabiler als der isomere Bicyclus.
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