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

• Gemini peptides were produced by disulfide bond linkage of the single-chain ones.
• The single-chain-to-gemini transition enhanced the self-assembly ability.
• Gemini geometry introduced additional constraints in molecular conformation.
• The intra- and intermolecular hydrogen bonding produced different structures.
• Peptide self-assembly depended greatly on 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 I3C–CI3 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.

The amphiphilic peptides self-assembled into different structures with variation of the side chain groups as well as the single-chain-to-gemini structural transition. The gemini geometry probably introduced additional constraints in molecular conformations and thus to result in specific molecular arrangements and self-assembled structures.Figure optionsDownload as PowerPoint slide