03 Fakultät Chemie

Permanent URI for this collectionhttps://elib.uni-stuttgart.de/handle/11682/4

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Institute: search.filters.UBSInstitut.Sonstige EinrichtungStart date: 1990End date: 1999

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Now showing 1 - 8 of 8
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    Properties of amphiphilic terminally substituted conjugated nonaene- and 2-docosylnonaene carboxylic acids in monolayers at the air-water interface
    (1991) Effenberger, Franz; Meller, Paul; Ringsdorf, Helmut; Schlosser, Hubert
    In the present communication, we report thesynthesis of conjugated nonaene- and 2-docosylnonaene carboxylic acids with different terminal substituents. These substituents have been chosen so that their spectroscopic properties differ from those of the polyene chain; they also have specific electron donor, electron acceptor or redox properties to allow for specific and selective excitation (energy intake). Because of the amphiphilic character of these compounds, pressure-area isotherms were determined in monolayers at the air-water interface.
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    Experimental and theoretical aspects of the formation of radical cations from tripyrrolidinobenzenes and their follow-up reactions
    (1990) Effenberger, Franz; Stohrer, Wolf-Dieter; Mack, Karl Ernst; Reisinger, Friedrich; Seufert, Walter; Kramer, Horst E.A.; Föll, Rudolf; Vogelmann, Ekehardt
    Tripyrrolidinobenzene radical cations(1*+), obtained from the corresponding arenes by oxidation with silver nitrate, are specially stabilized and thus allow specific reaction pathways of arene radical cations to be investigated separately and individually. Radical cations 1*+ ,for instance, generated under exclusion of oxygen, undergo dimerization to 2, or they abstract hydrogen from the solvent to form 3. In a pure oxygen atmosphere, the O2 reaction products 6 and 7 are formed, respectively, either exclusively or together with 2 and 3. Kinetic measurements give the following order of reactivity for these individual processes: reaction with O2 > dimerization. > H-abstraction from solvent. The changes in the product spectrum upon modification of the reaction conditions are in accord with the kinetic results. The dimeric u complexes 2 show surprisingly facile dissociation into two radical cations, two (1*+)with a much higher dissociation rate for the alkyl derivatives 2b-d than for 2a. Dissociation is enhanced substantially by light or in the presence of π donors. Individual product formation, rate of reactions of the radical cations 1*+, and photochemical cleavage of the dimeric σ complexes 2 can be rationalized, by qualitative and quantitative MO considerations, in terms of their relative frontier orbital energies.
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    Elektronen-Transfer bei den Reaktionen von Halogen-σ-Komplexen des 1,3,5-Tris(1-pyrro-lidinyl)benzols mit Nucleophilen (Aminobenzole ; 21)
    (1990) Effenberger, Franz; Bäuerle, Peter; Seufert, Walter; Stohrer, Wolf-Dieter
    Iodo, bromo, chloro, and thiocyanato σ-complexes 4, accessible as crystalline compounds from 1,3,5-tris(1-pyrrolidinyl)benzene (1) with halogens and dirhodan, respectively, react with nucleophiles or bases under dehalogenation, deprotonation, dimerization, or H σ-complex formation. The product formation depends on the redox potentials of the σ-complexes (acceptors) and the nucleophiles (donors), on the leaving tendency of the substituents on C-1 of the σ-complexes, and on the reaction time. The unexpected reactions are interpreted by an electron transfer from the nucleophile Y| to the σ-complex A+ to give the radical A*, a subsequent heterolytic dissociation to the 1,3,5-tris(1-pyrrolidinyl)benzene radical cation C.+, and its follow-up reactions (addition of nucleophiles, dimerization, and H abstraction). The H σ-complex 6 results the most stable final product after long reaction times because of its lowest acceptor properties and the poor nucleofugal leaving tendency of a hydride ion.
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    Photoregulation of α-chymotrypsin activity in organic media : effects of bioimprinting
    (1994) Willner, Itamar; Lion-Dagan, Mazzi; Rubin, Shai; Wonner, Johann; Effenberger, Franz; Bäuerle, Peter
    α-Chymotrypsin exhibits photoswitchable activities in an organic solvent after covalent modification of the protein backbone with thiophenefulgide active ester (2). The thiophenefulgide-modified α-chymotrypsin exhibits reversible photoisomerizable properties between states (3)-E and (3)-C. The modified α-chymotrypsin, where nine lysine residues are substituted by thiophenefulgide units, retains 60% of the activity of the native enzyme. The activities of thiophenefulgide-modified α-chymotrypsin toward esterification of N-acetyl-L-phenylalanine (4) by ethanol in cyclohexane are controlled by the configuration of the attached photoisomerizable component and by prior bioimprinting of the protein backbone with the reaction substrate (4). The esterification of (4) in cyclohexane using bioimprinted (3)-C is two-fold faster than in the presence of (3)-E. In the presence of a nonbioimprinted enzyme, esterification of (4) by (3)-C is five-fold faster than with (3)-E. The activity of bioimprinted (3)-E toward esterification of (4) is 4.5-fold higher than that of nonbioimprinted (3)-E. Switchable cyclic esterification of (4) is accomplished by sequential photoisomerization of the thiophenefulgide-modified α-chymotrypsin between states (3)-C and (3)-E.
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    Crystallization and preliminary X-ray diffraction studies of mandelonitrile lyase from almonds
    (1994) Lauble, Hanspeter; Müller, Kirsten; Schindelin, Hermann; Förster, Siegfried; Effenberger, Franz
    Single crystals of three different isoenzymes of (R)-(+) mandelonitrile lyase (hydroxynitrile lyase) from almonds (Prunus amygdalus) have been obtained by hanging drop vapor diffusion using polyethylene glycol 4000 and isopropanol as co-precipitants. The crystals belong to the monoclinic space group P2l with unit cell parameters a = 69.9, b = 95.1, c = 95.6 Å, and β = 118.5°. A complete set of diffraction data has been collected to 2.6 Å resolution on native crystals of isoenzyme III.
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    Photoswitchable binding of substrates to proteins : photoregulated binding of α-D-mannopyranose to concanavalin A modified by a thiophenefulgide dye
    (1992) Willner, Itamar; Rubin, Shai; Wonner, Johann; Effenberger, Franz; Bäuerle, Peter
    Macromolecules exhibiting photoswitchable physical or chemical properties are extensively examined as information storage and signal amplification materials. Photoregulated "on-of" biomaterials provide a novel means to design targeted therapeutic agents activated and deactivated by external light signals. Various means to photoregulate biotransformations by light-switchable enzymes have been described and include the modification of the enzyme active site and protein backbone by photochromic components and immobilization of enzymes in photochromic copolymers. Here we wish to report on the photoregulation of the binding properties of a protein by its chemical modification with photochromic units. We describe the photoswitchable binding of saccharides to concanavalin A modified by thiophenefulgide dye.
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    Konformation und Lichtabsorption von (2-Alkoxyvinyl)ethandionen (Chromophore Systeme ; 2)
    (1991) Effenberger, Franz X.; Kramme, Roland; Lindner, Hans Jörg; Martin, Georg; Martin, Hans-Dieter; Mayer, Bernhard
    The unusual color properties of yellow 1,2-bis(4,5-dihydrofuran-3-yl)ethane-1,2-dione (1) and colorless 1,2-bis(5,6-dihydro-4H-pyran-3-yl)ethane-1,2-dione (2) in the solid state and in solution are investigated by crystal structure analysis, UV-Vis, PE, and 13C-NMR spectroscopy as well as by reparameterized force-field calculations. Dione 1 takes an antiperiplaner CO/CO conformation of its chromophore in the solid state whereas dione 2 is twisted in this respect by 102°. In solution both chromophores are not planar, but 1 is less distorted (ca. 142°) than dione 2 (ca. 126°). The calculated rotational barrier for CO/CO twisting amounts to 0.9 kcal mol-1 for 1 and to 2.2 kcal mol-1 for 2.
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    Molekül- und Kristallstruktur der Phosphonsäure H3PO3 : Röntgen- und Neutronenbeugungsuntersuchungen an der Hydrogen- und der Deuterium-Verbindung (Wasserstoffbrücken ; 1)
    (1990) Becker, Gerd; Hausen, Hans-Dieter; Mundt, Otto; Schwarz, Wolfgang; Wagner, Claus-Thomas; Vogt, Thomas
    Die Struktur der Phosphonsäure H 3 PO 3 wurde mittels Neutronenbeugung (λ = 104,22 pm) an einem Einkristall bei 15,0 ± 0,1 K neu bestimmt, so daß Gitterparameter {Pna21; Z = 8; a = 716,6(3); b = 1201,3(5); c 674,3(3) pm} und Bindungslängen {Mittelwerte aus zwei kristallographisch unabhängigen Molekülen: P-O 155; P = O 150; P-H 139; O-H 101 pm} nun sehr genau (R = 0,053) bekannt sind. Jedes Molekül nimmt teil an vier unsymmetrischen Wasserstoff-Brückenbindungen (O...H 155 bis 160 pm; O-H...O 168 bis 177°), wobei die Hydroxyl-Gruppen als Donoren und die Phosphoryl-Fragmente als jeweils zweifache Akzeptoren auftreten. Insgesamt wird so ein komplexes, aus Maschen von vier und acht Knoten im Verhältnis 1:2 bestehendes Raumnetz aufgespannt, obwohl die Moleküle selbst verhältnismäßig übersichtlich im Sinne einer kubisch dichtesten Anordnung gepackt sind. Eine zum Vergleich bei 173 ± 3 K durchgeführte Röntgenstrukturanalyse (R = 0,032) ergab in den P-O-Abständen und O-P-O-Winkeln kaum nennenswerte Unterschiede; eine zusätzliche, vergleichende Neutronenbeugungsuntersuchung bei 15,0 ± 0,1 K ( λ= 131,68 pm; isotrope atomare Auslenkungsparameter) an der Hydrogen- (R = 0,044) und an der Deuterium-Verbindung (R = 0,041) führte zu weitgehend übereinstimmenden Strukturmodellen für die Isotopomeren.