Stereostructure Dependence Phenomenon on the Self-Assembly of Ala-Ala-Ala Lipotripeptides

A series of lipotripeptide stereoisomers based on alanine were synthesized, and their self-assembling behaviors were studied by means of circular dichroism spectra, ATR-IR, temperature-dependent H-1 NMR, and X-ray diffraction patterns. In the mixed solvent of hexafluoroisopropanol/H2O (1/9, v/v), eight lipotripeptides were able to self-assembled into nanoflakes or nanoribbons driven by the hydrophobic association of alkyl chains, intermolecular hydrogen bonding among carboxyl groups at C-terminal and amide groups of alanine moieties in the peptide segment. It was found that the stacking chirality of carbonyl groups was determined by the chirality of alanine residue at C-terminal (i.e., C-terminal determination rule). Moreover, our research also highlighted the intermolecular hydrogen bonding on amide groups of each alanine residue, terminal carboxyl as well as the molecular packing structures can be subtly manipulated by changing the stereochemical sequence of peptide segment.

Automated summary

The self-assembling behaviors of lipotripeptide stereoisomers based on alanine were studied, and it was found that they formed nanoflakes or nanoribbons through the hydrophobic association of alkyl chains and intermolecular hydrogen bonding. The stacking chirality of carbonyl groups was determined by the chirality of alanine residue at C-terminal. Furthermore, the stereochemical sequence of the peptide segment could subtly manipulate the intermolecular hydrogen bonding and molecular packing structures.