Helicity of perfluoroalkyl chains controlled by the self-assembly of the Ala-Ala dipeptides.

Four Ala-Ala dipeptides with a perfluoroalkyl chain at the N-terminal were synthesized. They were able to self-assemble into helical nanofibers and/or twisted nanobelts in a mixture of DMSO/H O. The handedness of nanofibers and nanobelts was controlled by the chirality of the alanine at the N-terminal.

Alignment of twisted nanoribbons formed by CHCO-Val-Ala sodium salts.

C17H35CO-l-Val-l-Ala and C17H35CO-d-Val-d-Ala sodium salts can form physical gels in water, and self-assemble into right- and left-handed twisted nanoribbons, respectively. FT-IR and 1H NMR spectra indicate that the H-bonding between the neighboring valine residues and electrostatic interactions of carboxylate groups play important roles in the formation of helical nanoribbons. Circular dichroism characterization and theoretical chemical calculations indicate that the dipeptide segments pack in a helical manner.