Influence of Chirality on the Self-Assembly of Dipeptides and Sensing of Fe3+

Chirality-controlled self-assembly of two small dipeptides was investigated. The N-terminal Fmoc and C-terminal methyl ester-protected dipeptides Fmoc-l-Ala-l-Val-OMe (1) and Fmoc-l-Ala-d-Val-OMe (2) adopted an intermolecular H-bonded parallel beta-sheet structure in the crystalline state. Different morphologies were observed for changing the chirality of Val. Peptides 1 and 2 exhibited micro- to nanolevel hollow tube and fibrillar morphology in an acetonitrile-water (1:1) mixture, respectively. These self-assembled structures were found to have significant thermal stability in dry heating. They could bind with bioactive dyes, e.g., thioflavin T, rhodamine B, fluorescein, and 5(6)-carboxyfluorescein. Interestingly, both peptides selectively sense the Fe3+ ions and may serve as fluorescence probes for the Fe3+ ions.