Self-assembly of amphiphilic peptides: Effects of the single-chain-to-gemini structural transition and the side chain groups.

By designing cysteine-containing single-chain peptides and then linking two such molecules with disulfide bond under oxidation, a series of amphiphilic gemini peptides were successfully synthesized. The gemini geometry introduced not only additional constraints in molecular conformations but also the differentiated intra- and intermolecular hydrogen bonding. These aspects result in specific transition of the self-assembly behavior. The single-chain peptides tended to form spherical aggregates, while the gemini molecules all self-assembled into fiber-like structures, especially that I 3 C–CI 3 could form short thin fibers with highly ordered lateral alignments that are rarely found. Moreover, the self-assembly of both the single-chain and the gemini peptides showed great dependence on the side chain groups. With increasing the size of the side chain alkyl groups, the molecules gave decreased critical aggregation concentration (CAC) and were more ready to arrange into ordered assemblies. This should be ascribed to the enhanced hydrophobic interaction and the subsequent force balance shifts. [ABSTRACT FROM AUTHOR]