Exploiting terminal charged residue shift for wide bilayer nanotube assembly.

HYPOTHESIS

Self-assembly of peptides is influenced by both molecular structure and external conditions, which dictate the delicate balance of different non-covalent interactions that driving the self-assembling process. The shifting of terminal charge residue is expected to influence the non-covalent interactions and their interplay, thereby affecting the morphologies of self-assemblies. Therefore, the morphology transition can be realized by shifting the position of the terminal charge residue.

EXPERIMENTS

The structure transition from thin nanofibers to giant nanotubes is realized by simply shifting the C-terminal lysine of ultrashort Ac-IK-NH to its N-terminus. The morphologies and detailed structure information of the self-assemblies formed by these two peptides are investigated systemically by a combination of different experimental techniques. The effect of terminal residue on the morphologies of the self-assemblies is well presented and the underlying mechanism is revealed.

FINDINGS

Giant nanotubes with a bilayer shell structure can be self-assembled by the ultrashort peptide Ac-KI-NH with the lysine residue close to the N-terminal. The Ac-KI-NH dimerization through intermolecular C-terminal H-bonding promotes the formation of a bola-form geometry, which is responsible for the wide nanotube assembly formation. The evolution process of Ac-KI-NH nanotubes follows the "growing width" model. Such a morphological transformation with the terminal lysine shift is applicable to other analogues and thus provides a facile approach for the self-assembly of wide peptide nanotubes, which can expand the library of good template structures for the prediction of peptide nanostructures.