Self-organization of amide dendrons with focal dipeptide units

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/H ₂O (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 H ₂O 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.