Self-organization of amide dendrons with focal dipeptide units

Abstract

Dendron–dipeptide conjugates were synthesized to investigate their self-assembly characteristics not only in the aqueous phase but also in organic media. In the aqueous phase, the self-organized structure of 2G-PhePhe and 2G-GlyGly was influenced predominantly by the self-assembly characteristics of the amide dendron unit to exhibit vesicular structures. For 1G-PhePhe and 1G-GlyGly, however, the role of the focal dipeptide unit became important to show donut-like assemblies and rod-like structures, respectively. In HFIP/H₂O (1 : 100 v/v), 2G-PhePhe and 1G-PhePhe exhibited donut-like structures, while 2G-GlyGly and 1G-GlyGly formed rod-like structures. The secondary structures of the dendron–peptide conjugates were remarkably influenced by the dendron unit. The circular dichroism (CD) spectra showed that 1G-PhePhe in H₂O adopted the β-sheet structure. On increasing the generation of the dendron unit, on the other hand, 2G-PhePhe did not adopt the β-sheet structure but exhibited random structures. In addition, the curvature of the assembled structure of the dendron–peptide conjugates was affected by the dendron unit. In organic media such as toluene, all the dendron–dipeptide conjugates formed fibrous structures which could induce thermoreversible gel formation. Therefore, the modulation of the dendritic moiety and the focal peptide unit provided an opportunity to produce diverse self-organized structures in various conditions.