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  • 1
    Electronic Resource
    Electronic Resource
    A crossed laser-molecular beam study of the one and two photon dissociation dynamics of ferrocene at 193 and 248 nm (1989)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 90 (1989), S. 4248-4257 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: A crossed laser-molecular beam study of the one and two photon dissociation mechanism of bis (cyclopentadienyl) iron (ferrocene, FeCp2) has been performed at 193 and 248 nm. By combining electron bombardment mass spectroscopy with time-of-flight (TOF) measurements, the photodissociation mechanism at 193 nm is shown to have two distinct mechanisms. (1) FeCp2+hν→FeCp*+Cp; (2) FeCp+2hν→FeCp+Cp, FeCp→Fe+Cp. For the first mechanism, which accounts for less than 5% of the photodissociation events, the FeCp* velocity distribution is quantitatively consistent with a statistical dissociation producing FeCp in an excited, ligand field electronic state. The velocity distributions of the Cp and Fe fragments produced by the second mechanism (FeCp is an unstable intermediate) are also in excellent agreement with microcanonical calculations for both Cp elimination steps using the known metal–ligand bond energies of ferrocene. For the second mechanism, dissociation occurs on the lowest potential energy surface for each Cp elimination. Although one photon is energetically sufficient to remove one Cp ligand from ferrocene, RRKM calculations of the lifetime indicate that Cp elimination is extremely slow for dissociation along the ground electronic state potential energy surface. Hence, after internal conversion to the ground electronic state, the large photon absorption cross section (∼4 A(ring)2) for the experimental irradiation conditions allows additional photons to be absorbed until the dissociation rate exceeds the up pumping rate. The large photon energy causes the dissociation rate to increase by many orders of magnitude for each additional photon absorbed. Consequently, there is strong selectivity for the total number of photons absorbed. Both mechanisms, occurring on two different electronic potential energy surfaces, suggest that dissociation induced by excitation of the ligand-to-metal charge transfer states accessed at 193 nm can be quantitatively described as a statistical, unimolecular decomposition. At 248 nm, the measured product velocity distributions are qualitatively consistent with the mechanism deduced from the 193 nm results, but the energy available for translation at this wavelength is too small to extract quantitative producttranslational energy distributions which are required to independently test the applicability of the statistical dissociation model.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.455781
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  • 2
    Electronic Resource
    Electronic Resource
    2'-Fluorinated arabinonucleosides of 5-(2-haloalkyl)uracil: synthesis and antiviral activity (1987)
    s.l. : American Chemical Society
    Journal of medicinal chemistry 30 (1987), S. 1199-1204 
    Details
    ISSN: 1520-4804
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/jm00390a013
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  • 3
    Electronic Resource
    Electronic Resource
    Nucleotide sequence of arfB of Clostridium stercorarium, and prediction of catalytic residues of α-l-arabinofuranosidases based on local similarity with several families of glycosyl hydrolases (1998)
    Oxford, UK : Blackwell Publishing Ltd
    FEMS microbiology letters 164 (1998), S. 0 
    Details
    ISSN: 1574-6968
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: The nucleotide sequence of the α-l-arabinofuranosidase gene arfB from Clostridium stercorarium was determined. The deduced protein has a molecular mass of 56.2 kDa with an amino terminus identical to the N-terminal sequence of the purified mature enzyme from C. stercorarium. Its sequence is homologous to arabinofuranosidases of glycosyl hydrolase family 51. Sequence alignment and cluster analysis reveal three new members of glycosyl hydrolase family 51, allowing for the definition of highly conserved regions. Two of these regions are remarkably similar to the most conserved regions within several other families of glycosyl hydrolases, which have in common a (β/α)8-barrel as the core super-secondary structure, and allow to predict the acid/base catalyst and the nucleophile of the active site.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1574-6968.1998.tb13107.x
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  • 4
    Electronic Resource
    Electronic Resource
    Still another proof of Parseval's equation for almost-even arithmetical functions (1988)
    Springer
    Aequationes mathematicae 35 (1988), S. 132-139 
    Details
    ISSN: 1420-8903
    Keywords: Primary 11K65 ; Secondary 11N37, 11A25, 43A60
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics
    Notes: Abstract Still another proof is given for Parseval's well-known equation $$\sum\limits_{1 \leqslant r〈 \infty } {|a_r |^2 \cdot \varphi (r) = \parallel f\parallel \begin{array}{*{20}c} 2 \\ 2 \\ \end{array} } $$ forB 2-almost-even arithmetical functionsf with Ramanujan coefficients $$a_r = \frac{1}{{\varphi (r)}} \cdot M(f \cdot c_r )$$ . An explicit “best approximation” off by even functions, constructed from characteristic functions of subsets {n; g.c.d.(n, r) =k} ⊂ $$\underset{\raise0.3em\hbox{$\smash{\scriptscriptstyle\cdot}$}}{\mathbb{N}} $$ is used.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01830940
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  • 5
    Electronic Resource
    Electronic Resource
    High-level expression of Clostridium thermocellum cellulase genes in Escherichia coli (1987)
    Springer
    Applied microbiology and biotechnology 27 (1987), S. 50-56 
    Details
    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Summary The Clostridium thermocellum cellulase genes celA and celC encoding endoglucanase A and C were subcloned in a temperature-regulated Escherichia coli expression vector containing the leftward promoterpl of bacteriophage lambda. The level of gene expression was controlled by thermal inactivation of the heat-sensitive lambda cI857 repressor. Under optimal conditions the recombinant endoglucanases A and C were expressed to a level of 10–15% of total cellular protein. Endoglucanase A was partially exported into the periplasmic space, whereas endoglucanase C was found sequestered within the cytoplasm. Overexpression of the celA gene resulted in decreased cell viability concomitant with the accumulation of endoglucanase A in the membrane fraction. In contrast, high-level synthesis of the celC gene product was well tolerated by the host cell. Overproduced endoglucanase C accumulated as a soluble enzyme without detectable formation of inactive inclusion bodies.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00257253
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  • 6
    Electronic Resource
    Electronic Resource
    Degradation of barley β-glucan by endoglucanase C of Clostridium thermocellum (1988)
    Springer
    Applied microbiology and biotechnology 29 (1988), S. 25-31 
    Details
    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Summary Endoglucanase C encoded by the celC gene of Clostridium thermocellum has been purified to homogeneity from a recombinant Escherichia coli strain. It was found that this enzyme is highly efficient in degrading glucans with alternating β-1,4- and β-1,3-linkages but lacks activity on unmodified cellulosic substrates. The properties of endoglucanase C were compared to those of Bacillus subtilis β-glucanase, an enzyme used in the brewing industry for β-glucan degradation. Both enzyme cause a rapid decrease of the viscosity of barley β-glucan as a result of internal chain cleavage. Endoglucanase C hydrolyses non-specifically β-1,3- and β-1,4-bonds adjacent to unsubstituted or 4-O′-substituted cellobiose units. Due to its lower pH optimum and increased thermostability endoglucanase C compares favourably with B. subtilis β-glucanase and seems suitable for use in the mashing process of beer brewing.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00258346
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  • 7
    Electronic Resource
    Electronic Resource
    5-Ethylthiomethyl- und 5-Ethylsulfonylmethylpyrimidine (1986)
    Springer
    Monatshefte für Chemie 117 (1986), S. 385-392 
    Details
    ISSN: 1434-4475
    Keywords: Halogen exchange, in pyrimidines ; Pyrimidines, 5-ethylsulfonyl-methyl- ; Pyrimidines ; 5-ethylthiomethyl-
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract In 2,4-dichloro-5-ethylthiomethylpyrimidines3a, b and in (2,4-dichloro-5-pyrimidinylmethyl)ethyl sulfones5a, b, resp., by reaction with ammonia, diethyl-amine, isopropylamine, sodium methanolate and sodium ethylthiolate, resp., the halogen atoms have been substituted by amino, methoxy or ethylthio groups, resp., and thus the compounds4a–4r and5c–5f have been obtained.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00816533
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  • 8
    Electronic Resource
    Electronic Resource
    Stickelberger ideal and signature of circular units (1996)
    Springer
    Mathematische Zeitschrift 223 (1996), S. 1-11 
    Details
    ISSN: 0025-5874
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/PL00004269
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  • 9
    Electronic Resource
    Electronic Resource
    Organisation changes in the editorial office of chromatographia (1998)
    Springer
    Chromatographia 47 (1998), S. 5-5 
    Details
    ISSN: 1612-1112
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02466777
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  • 10
    Electronic Resource
    Electronic Resource
    Coordination Modes of 2,5-Di(tert-butyl)pyrrolide - Crystal Structures of HPyr*, Pyr*H·thf, (thf)2LiPyr*, and [(Me3Si)3C-Zn]2(μ-Cl)(μ-Pyr*) (Pyr* = 2,5-tBu2NC4H2) (1998)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 1998 (1998), S. 1175-1182 
    Details
    ISSN: 1434-1948
    Keywords: Hydrogen bonds ; Indium ; Lithium ; Nitrogen heterocycles ; Zinc ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The lithiation of 2,5-di(tert-butyl)pyrrole (1) yields bis(tetrahydrofuran)lithium 2,5-di(tert-butyl)pyrrolide (2), which is monomeric in solution as well as in the solid state. Due to the coordination number of three for the lithium atom, short Li-O and Li-N bond lengths of 193 pm are observed. The metathesis reaction of 2 with tris(trimethylsilyl)-methylzinc chloride (3) gives colorless bis[tris(trimethyl-silyl)methylzinc] chloride 2,5-di(tert-butyl)pyrrolide (4). The pyrrolide ligand and the chlorine atom bridge the zinc atoms. One of the zinc atoms is bonded to the nitrogen atom of the pyrrolide substituent, while the other bonds to the opposite C-C bond. At 215 pm, the Zn-N bond is very long compared to those in alkylzinc amides, whereas the Zn-C distances lie in the range of Zn-C bond lengths found between zinc and η5-bonded cyclopentadienide ligands. The molecular structures of 1 and of the low-melting THF adduct 1·thf show a similar 2,5-di(tert-butyl)pyrrole molecule, but in the latter case a weak N-H···O bond is observed (N-H 97 pm, O···H 199 pm).
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