期刊
CHEMISTRY-A EUROPEAN JOURNAL
卷 15, 期 2, 页码 388-404出版社
WILEY-V C H VERLAG GMBH
DOI: 10.1002/chem.200801668
关键词
acetylenes; oligopeptides; organogels; self-assembly; supramolecular chemistry
资金
- Fonds der Chemischen Industrie (Fonds-Stipendium Eike Jahnke)
- ETH Zurich [TH-70 07-1]
- Schweizerischer Nationalfonds [200021-113509]
- Deutscher Akademischer Austauschdienst (DAAD-Stipendien Jan Weiss, Sonja Neuhaus)
A series of functional iodoacetylenes was prepared and converted into the corresponding diacetylene-substituted amino acids and peptides via Pd/Cu-promoted sp-sp carbon cross-coupling reactions. The unsymmetrically substituted diacetylenes can be incorporated into oligopeptides without a change in the oligopeptide strand's directionality. Thus, a series of oligopeptide-based, amphiphilic diacetylene model compounds was synthesized. and their self-organization as well as their UV-induced topochemical polymerizability was investigated in comparison to related polymer-substituted macromonomers. Solution-phase IR spectroscopy, gelation experiments, and UV spectroscopy helped to confirm that a minimum of five N-H center dot center dot center dot O=C hydrogen-bonding sites was required in order to obtain reliable aggregation into stable beta-sheet-type secondary structures in organic solvents. Furthermore, the non-equidistant spacing of these hydrogen-bonding sites was proven to invariably lead to beta-sheets with a parallel beta-strand orientation, and the characteristic IR-spectroscopic signatures of the latter in organic solution was identified. Scanning force micrographs of the organogels revealed that compounds with six hydrogen-bonding sites gave rise to high aspect ratio nanoscopic fibrils with helical superstructures but, in contrast to the related macromonomers, did not lead to uniform supramolecular polymers. The UV-induced topochemical polymerization within the beta-sheet aggregates was Successful, proving parallel beta-strand orientation and highlighting the effect of the number and pattern of N-H center dot center dot center dot O=C hydrogen-bonding sites its well as the hydrophobic residue in the molecular structure on the formation of higher structures and reactivity.
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