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  • 1
    ISSN: 1432-2234
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Zusammenfassung Rechnungen unter Einschluß aller Elektronen wurden unter Verwendung von Gaußfunktionen mit dem Programm IBMOL für Propylen in zwei verschiedenen Konformationen durchgeführt. Nach dem van der Waals-Modell von Mason und Kreevoy, das für zahlreiche Moleküle die Gleichgewichtskonformation richtig vorauszuberechnen gestattet, sollte die Konformation, in der die CH2-Gruppe einem der H-Atome der Methylgruppe gegenübersteht, am wenigsten stabil sein, während Mikrowellenmessungen das Gegenteil bewiesen. Nach den SCF-Rechnungen, deren Ergebnisse mit dem experimentellen Befund im Einklang stehen, scheint eine Wechselwirkung der Methylgruppe mit demπ-Elektronensystem der Vinylgruppe einer der stabilisierenden Faktoren der Gleichgewichtskonformation zu sein.
    Abstract: Résumé Le programme IBMOL a été utilisé pour le calcul SCF LCAO MO de deux conformations différentes du propylène. Selon le modèle Van der Waals de Mason et Kreevoy qui prédit correctement les conformations d'équilibre dans un certain nombre de molécules, la conformation où le groupe CH2 se trouve masqué par un des atomes d'hydrogène du groupe méthyle ne devrait pas être aussi stable que la conformation étoilée, alors que des mesures micro-ondes prouvent le contraire. Les résultats du calcul SCF sont en accord avec l'expérience et indiquent que l'interaction du groupe méthyle avec les électronsπ du groupe vinyle peut être l'un des facteurs qui stabilisent le conformation éclipsée.
    Notes: Abstract For two different conformations of propylene all-electron SCF-LCAO-MO calculations were performed with the program IBMOL using Gaussian basis functions. According to the van der Waals model of Mason and Kreevoy which correctly predicts the equilibrium conformations in a number of molecules, the conformation with the CH2 group eclipsed by one of the hydrogen atoms of the methyl group should be not as stable as the corresponding staggered conformation, but microwave measurements proved the eclipsed conformation to be the more stable. The results of the SCF-calculations agree with the experiment and indicate that the interaction of the methyl group with theπ-electron system of the vinyl group may be one of the factors stabilizing the eclipsed conformation.
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  • 2
    ISSN: 1432-2234
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Abstract A quantum mechanical model of complex compounds is discussed. Eigenfunctions of a one center problem are used and chosen in a manner so that they correspond to many-center functions (MO-LCAO-functions) with regard to the form and the number of their zero surfaces as closely as possible, having the same group theoretical transformation properties. Calculations on Ti(III)-complexes are made assuming a 37-electron problem and using one variational and one model parameter only. The model gives the correct sequential order of the terms 2 T 2g ,2 E g and 2 T 1u and the correct order of magnitude of the term differences.
    Abstract: Résumé On discute un modèle où les fonctions monoélectroniques multicentriques d'une molécule sont approximées par des fonctions qui leur ressemblent si bien que possible quant au nombre et l'espèce des surfaces nodales, et qui appartiennent aux représentations correspondantes. Les complexes du Ti 3+ sont ainsi traites en problème à 37 électrons avec deux paramètres, l'un variationnel et l'autre libre. Les états 2 T 2g ,2 E g et 2 T 1u résultent en ordre correct et avec des différences d'énergie du juste ordre de grandeur.
    Notes: Zusammenfassung Es wird ein quantenmechanisches Modell diskutiert, dem die Idee zugrunde liegt, zur theoretischen Behandlung von Komplexverbindungen Eigenfunktionen eines Zentralproblems zu benutzen und diese so zu bestimmen, daß sie hinsichtlich Art und Zahl ihrer Knoten-flächen möglichst gut den Knotenflächen von Mehrzentrenfunktionen (MO-LCAO-Funktionen) entsprechen, bei Übereinstimmung hinsichtlich des gruppentheoretischen Transformations-verhaltens. Ti(III) -Komplexe werden als 37-Elektronenprobleme mit Hilfe eines Variations-parameters und eines freien Parameters behandelt. Die Terme 2 T 2g ,2 E g und 2 T 1u resultieren in der richtigen Reihenfolge und mit größenordnungsmäßig richtigen Termdifferenzen.
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Theoretical chemistry accounts 35 (1974), S. 301-308 
    ISSN: 1432-2234
    Keywords: Vinylsilane ; Hyperconjugation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Ab initio calculations were performed for SiH3-CH=CH2 and CH3-CH=CH2. They lead to the result that the bathochromic shift observed in the spectra when replacing the methyl group of propylene by a silyl group can be explained by differences in the hyperconjugation between the silyl- or methyl-group and the vinyl rest of the molecules. This result is gained qualitatively correct already without including silicon d-functions. The inclusion of silicon d-functions is helpful for a quantitatively accurate description. The d-function participation gains within the functional basis employed here considerable weight in the excited states only.
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  • 4
    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract  The influence of increased dissolved O2 concentrations (DOC) on cell growth and production of the secondary metabolite manumycin by a strain of Streptomyces parvulus (Tü 64) was investigated in a stirred tank fermentor. DOC is given as the O2 partial pressure (pO2) in the gas phase in an equilibrium state with the liquid phase. Growth of S. parvulus was not influenced up to DOC equivalent to pO2=1260 mbar. At pO2=2205 mbar the maximum biomass concentration was lowered by 40%. Production of manumycin was markedly influenced by DOC and reached the maximal concentration at pO2=315 mbar. At increased DOC three new metabolites were observed. Two of them, 64p-A and 64p-B, were identified as carboxamides, which represent the branched side chain of the manumycin molecule and a derivative with a shorter chain length. The third metabolite, 64p-C, was a manumycin derivative containing an aromatic ring system. Feeding of glycerol during the production phase increased the total yield and showed a similar effect of DOC. Since DOC has significant regulation effects on product formation and selectivity, it should be used as a major parameter in development strategies of aerobic microbial processes.
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  • 5
    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract The influence of enhanced O2 concentration on growth and formation of secondary metabolites by Streptomyces griseoflavus (strain Tü 2880) was investigated in a stirred tank and in an air-lift fermentor. At a partial pressure of O2 pO2=1880 mbar the growth was lowered by 50% compared to pO2=210 mbar, whilst substrate consumption and O2 uptake rate increased markedly. Production of the colabomycin complex reached maximum values at pO2=630 mbar. A similar increase of secondary metabolite formation was obtained when glycerol or acetate were fed at pO2=220 mbar. The portion of the derivate colabomycin A in the product mixture rose from 43% at pO2=210 mbar to 73% at pO2=1260 mbar. Since dissolved O2 concentration has a significant influence on productivity and selectivity it may be used to regulate aerobic fermentation processes.
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  • 6
    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract The influence of increased dissolved O2 concentrations (DOC) on cell growth and production of the secondary metabolite manumycin by a strain of Streptomyces parvulus (Tü 64) was investigated in a stirred tank fermentor. DOC is given as the O2 partial pressure (po 2) in the gas phase in an equilibrium state with the liquid phase. Growth of S. parvulus was not influenced up to DOC equivalent to po 2 = 1260 mbar. At po 2 = 2205 mbar the maximum biomass concentration was lowered by 40%. Production of manumycin was markedly influenced by DOC and reached the maximal concentration at po 2 = 315 mbar. At increased DOC three new metabolites were observed. Two of them, 64p-A and 64p-B, were identified as carboxamides, which represent the branched side chain of the manumycin molecule and a derivative with a shorter chain length. The third metabolite, 64p-C, was a manumycin derivative containing an aromatic ring system. Feeding of glycerol during the production phase increased the total yield and showed a similar effect of DOC. Since DOC has significant regulation effects on product formation and selectivity, it should be used as a major parameter in development strategies of aerobic microbial processes.
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  • 7
    ISSN: 1423-0445
    Keywords: Key words. pheromone - sex pheromone - egg release pheromone - marine invertebrate - polychaete - Nereis succinea - inosine - nucleoside - glutamic acid - glutamine
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary. Pheromones released by male marine polychaetes Nereis succinea (Frey & Leuckart 1847) initiate egg release in mature females. Here we describe isolation and identification of components of the egg release pheromone bouquet from the coelomic fluid of sexually mature males. Inosine, L-glutamic acid and L-glutamine are identified to be components. Inosine, an egg release component, has a response threshold that is reduced eightfold by simultaneous presentation 1 : 1 with L-glutamic acid or L-glutamine. A fourth substance in the bouquet is tentatively identified as guanosine. The natural relative concentrations of all members of the pheromone bouquet and their mutual influence must still be explored.
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  • 8
    ISSN: 1423-0445
    Keywords: Key words. sex pheromone - marine invertebrates - marine polychaetes - Nereis succinea - sperm release - cysteine-glutathione disulfide - glutathione - peptides
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary. In the marine polychaete Nereis succinea (Frey & Leuckart 1847) a sex pheromone was isolated from the coelomic fluid of sexually mature females and identified by NMR studies and independent synthesis. This pheromone is released by the females during reproduction together with eggs and coelomic fluid into the free water column and induces sperm release of surrounding males. Its structure was ascertained as L-cysteine-glutathione disulfide. It exhibited a response threshold of 0.6 · 10−7 M.
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  • 9
    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract The influence of enhanced O2 concentration on growth and formation of secondary metabolites byStreptomyces griseoflavus (strain Tü 2880) was investigated in a stirred tank and in an air-lift fermentor. At a partial pressure of O2 po2 = 1880 mbar the growth was lowered by 50% compared to po2 = 210 mbar, whilst substrate consumption and O2 uptake rate increased markedly. Production of the colabomycin complex reached maximum values at po2 = 630 mbar. A similar increase of secondary metabolite formation was obtained when glycerol or acetate were fed at po2 = 220 mbar. The portion of the derivate colabomycin A in the product mixture rose from 43% at po2 = 210 mbar to 73% at po2 = 1260 mbar. Since dissolved O2 concentration has a significant influence on productivity and selectivity it may be used to regulate aerobic fermentation processes.
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  • 10
    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract The influence of enhanced O2 concentration on growth and formation of secondary metabolites byStreptomyces griseoflavus (strain Tü 2880) was investigated in a stirred tank and in an air-lift fermentor. At a partial pressure of O2 po2 = 1880 mbar the growth was lowered by 50% compared to po2 = 210 mbar, whilst substrate consumption and O2 uptake rate increased markedly. Production of the colabomycin complex reached maximum values at po2 = 630 mbar. A similar increase of secondary metabolite formation was obtained when glycerol or acetate were fed at po2 = 220 mbar. The portion of the derivate colabomycin A in the product mixture rose from 43% at po2 = 210 mbar to 73% at po2 = 1260 mbar. Since dissolved O2 concentration has a significant influence on productivity and selectivity it may be used to regulate aerobic fermentation processes.
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