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Zur Struktur von Eumelaninen : Identifizierung von Konstitutionsmustern durch Festkörper-NMR-Spektroskopie / On the Structure of Eumelanins : Identification of Constitutional Patterns by Solid-state NMR SpectroscopyPeter, Martin G., Förster, Hans January 1989 (has links)
Aus dem Inhalt:
Melanine sind komplexe polyphenolische Polymere. In
der Natur entstehen sie durch meist enzymkatalysierte
oxidative Polymerisation von o-Diphenolen. Man unterscheidet die aus Dopa 1 oder Dopamin 3 hervorgehenden, tiefschwarzen Eumelanine von den aus Dopa in Gegenwart von Cystein entstehenden, gelben bis braunen Phaomelaninen. [...]
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Polymerization of hydrocarbon and fluorocarbon amphiphiles in Langmuir-Blodgett multilayersLaschewsky, André, Ringsdorf, H., Schmidt, G. January 1985 (has links)
Langmuir-Blodgett multilayers of polymerizable carboxylic acids with hydrocarbon or fluorocarbon chains were prepared. The multilayers were polymerized by UV light and the reactions were studied by UV/visible spectroscopy. The polyreactions strongly influence the multilayer structures which were investigated by X-ray small-angle scattering and scanning electron microscopy. The spreading behaviour of the monomers, the preparation of multilayers, their reactivities in multilayers and structural effects caused by the polyreactions are discussed with regard to the hydrophilic head groups, the polymerizable groups and the hydrophobic chains.
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Photodimerization and photopolymerization of amphiphilic cinnamic acid derivatives in oriented monolayers, vesicles and solutionKoch, Horst, Laschewsky, André, Ringsdorf, Helmut, Teng, Kang January 1986 (has links)
Cinnamic acid moieties were incorporated into amphiphilic compounds containing one and two alkyl chains. These lipid-like compounds with photoreactive units undergo self-organization to form monolayers at the gas-water interface and bilayer structures (vesicles) in aqueous solutions. The photoreaction of the cinnamic acid moiety induced by 254 nm UV light was investigated in the crystalline state, in monolayers, in vesicles and in solution in organic solvents. The single-chain amphiphiles undergo dimerization to yield photoproducts with twice the molecular weight of the corresponding monomers in organized systems. The photoreaction of amphiphiles containing two cinnamic acid groups occurs via two mechanisms: The intramolecular dimerization produces bicycles, with retention of the molecular weight of the corresponding monomer. The intermolecular reaction leads to oligomeric and polymeric photoproducts. In contrast to the single-chain amphiphiles, photodimerization processes of lipoids containing two cinnamic acid moieties also occur in solution in organic solvents.
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Oriented supramolecular systems-polymeric monolayers and multilayers from prepolymerized amphiphilesLaschewsky, André, Ringsdorf, H., Schneider, J. January 1986 (has links)
Oriented polymeric membranes were originally prepared by polymerization or polycondensation of preoriented monomers. The introduction of hydrophilic spacer groups into the polymeric amphiphiles allowed the formation of highly ordered systems (monolayers, liposomes, multilayers) from prepolymerized amphiphiles: due to the partial decoupling of the different mobilities and orientation tendencies of the polymer chain and the amphiphilic side groups, these polymers are able to self-organize. In monolayer experiments the high order of these membranes could be demonstrated by their surface pressure area-diagrams. In addition the combination of order and mobility of these spacer groups containing polymeric amphiphiles allowed the formation of Langmuir-Blodgett-multilyers with a high layer correlation. Thus, disturbancies in highly oriented layers can be avoided normally taking place during the polymerization reaction (e.g. contractions) or oriented monomeric layers.
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Self-organization of polymeric lipids with hydrophilic spacers in side groups and main chain : investigation in monolayers and multilayersLaschewsky, André, Ringsdorf, H., Schmidt, G., Schneider, J. January 1987 (has links)
Several polymerizable lipids were synthesized and polymerized to amphiphilic homopolymers and to copolymers with the help of hydrophilic comonomers. The self-organization of these polymeric lipids was investigated in monolayers and
Langmuir-Blodgett multilayers. The self-organization of these polymers in model membranes is due to hydrophilic spacer groups in the amphiphilic side groups as well as to hydrophilic spacer groups in the polymer backbone. Thus, highly ordered
monolayers and LB-multilayers are easily obtained.
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Polymerization of amphiphilic dienes in Langmuir-Blodgett multilayersLaschewsky, André, Ringsdorf, H. January 1988 (has links)
Amphiphilic derivatives of octadiene and docosadiene were investigated in monolayers and Langmuir-Blodgett multilayers, with respect to their self-organization and their polymerization behavior. All amphiphiles investigated form monolayers. However, only acid and alcohol derivatives were able to build up multilayers. Those multilayers are rapidly photopolymerized in the layers via a two-step process: Irradiation with long-wavelength UV light yields soluble polymers, whereas additional irradiation with sfiort-wavelength
UV light produces insoluble and presumably cross-linked polymers. The reaction meclianism is discussed according to the polymer characterization by UV spectroscopy, small-angle X-ray scattering, NMR spectroscopy, and gel permeation chromatography. All multilayers undergo structural changes during the polymerization; substantial changes result in defects in the polymerized layers as observed by scanning electron microscopy.
In contrast to the acids and alcohols, the deposition of monolayers of the aldehyde derivatives did not yield well-ordered multilayers, but rather amorphous films. In this different film structure, the photopolymerization
process differs from the one observed in multilayers.
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Mixed polymeric monolayers and Langmuir-Blodgett multilayers with functional low molecular weight guest compoundsLaschewsky, André, Paulus, W., Ringsdorf, Helmut, Schuster, A., Frick, G., Mathy, A. January 1992 (has links)
Mixed monolayers and Langmuir-Blodgett multilayers of functional low molecular weight guest compounds, especially nonlinear optical (NLO) dyes, within the matrix of an amphotropic spacer polymer have been prepared. The polymer matrix enabled the transfer of guest compounds not capable of self-organizing at the air-water interface by themselves. The structure of the LB multilayers and the transfer process were studied by small angle X-ray scattering and UV-visible spectroscopy. Good NLO coefficients were found in the mixed films.
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Thermal behaviour of polymeric Langmuir-Blodgett multilayersErdelen, C., Laschewsky, André, Ringsdorf, H., Schneider, J., Schuster, A. January 1989 (has links)
Langmuir-Blodgett multilayers of hydrocarbon and fluorocarbon polymers with hydrophilic spacer, lipid-polyelectrolyte complexes and mesogenic polymers have been prepared. The thermal behaviour of the multilayers was studied by small angle X-ray scattering, IR and UV—visible spectroscopy. Good thermal stabilities were found for the various classes of polymers. In addition, for both complexed multilayers and mesogenic polymer films, reorientation processes were observed.
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Monolayers and Langmuir-Blodgett multilayers of discotic liquid crystals?Laschewsky, André January 1989 (has links)
Contents:
1. Discotic Liquid Crystals
2. Monolayers and Langmuir-Blodgett Multilayers
3. Theoretical Considerations on the Molecular Packing of Discotic LCs in Monolayers and Multilayers
4. Spreading Experiments with Discotic LCs
5. LB-Multilayers of Discotic LCs
6. Polymeric Discotic LCs
7. Summary
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Catecholamine-protein conjugates : isolation of 4-phenylphenoxazin-2-ones from oxidative coupling of N-acetyldopamine with alipathic amino acidsPeter, Martin G., Andersen, Svend Olav, Hartmann, Rudolf, Miessner, Merle, Roepstorff, Peter January 1992 (has links)
4-Phenylphenoxazinones were isolated after biomimetic oxidation, using diphenoloxidases of insect cuticle, mushroom tyrosinase, or after autoxidation of N-acetyldopamine (Image ) in the presence of β-alanine, β-alanine methyl ester or N-acetyl-L-lysine. They are formed presumably by addition of 2-aminoalkyl-5-alkylphenols to the o-quinone of biphenyltetrol which, in turn, arises from oxidative coupling of. The structures of present the first examples for the assembly of reasonably stable intermediates in the rather complex process of chemical modifications of aliphatic amino acid residues by o-quinones.
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