Nanofiber formation of amphiphilic cyclic tri-beta-peptide

A novel amphiphilic cyclic peptide composed of two beta-glucosamino acids and one trans-2-aminocyclohexylcarboxylic acid was synthesized and investigated on assembly formation. The cyclic tri-beta-peptide was self-assembled into rodlike crystals or nanofibers depending on preparative conditions. The rodlike crystals showed a layer spacing of 4.8 A along the long axis, and columnar spacings of 10.8 and 21.5 A by electron diffraction analysis along the short axis. The former confirms the columnar structure upon molecular stacking, and the latter indicates triple bundle formation of the columnar assemblies. Fourier transform infrared (FT-IR) measurement of the fibrous assembly showed formation of homogeneous hydrogen bonds among amide groups, also supporting the molecular stacking of cyclic beta-peptides. Straight nanofibers with uniform diameter were also uniquely obtained.