A “Center-determination” Phenomenon of C13H27CO-Gly-Ala-Ala Lipotripetides: Relationship between Molecular Chirality and Handedness of organic self-assembly

A series of C13H27CO-Gly-Ala-Ala tripeptides with different chirality are synthesized. They can cause physical gels in toluene and 1,4-dioxane. They self-assemble into right- or left-handed twisted nanoribbons in a mixture of methanol and water. It is found that the handedness of the nanoribbons is controlled by the chirality of the alanine residue at the center. Circular dichroism characterizations also indicated that the peptide segments packing handedness was dominated by the chirality of the central alanine residue. The formation of the self-assemblies was studied using 1H NMR and particle size distribution. With decreasing temperature, micelle changes to fine aggregate and then grows into twisted nanoribbons. It was also found from the 1H NMR characterization that H-bonds formed by the central alanine played an important role in the formation of the self-assemblies. X-ray diffraction patterns showed that the tripeptides packed into lamellar structures.