(692h) Water-Vapor Responsive Metallo-Peptide Nanofibers

Short peptides are commonly used to construct supramolecular materials. Most reported peptide materials are hydrophobic and stiff and show a limited response to external stimuli in the solid state. In this work, we describe a series of supramolecular metallo-peptide nanofibers that, depending on their sequence, change stiffness and reversibly assemble in the solid state in response to changes in relative humidity (RH). We tested a histidine (H) series containing dipeptides with varying hydrophobicities, XH, where X is Glycine(G), Alanine(A), Leucine(L), and tyrosine(Y). Metal coordination with Zinc and dynamic H-bonds supports the one-dimensional fiber formation. Specifically, the solvent mixture was tuned for GH/Zn and AH/Zn sequences to obtain gels that gave rise to nanofibers upon air-drying. When these nanofiber networks were exposed to high relative humidity, a reduction in stiffness and a reversible disassembly between 60–70 % RH were observed. This assembly/disassembly process was possible because of the balance of hydrogen bonding interactions between the peptides and water. The RH-responsive actuation was tested upon the deposition of these nanofibers on the surface of a polyimide film; when the relative humidity varied, the peptide/water interactions in the solid state mechanically transferred to the polymer film, resulting in the rapid and reversible folding-unfolding of the films. Thus, demonstrating the possibility of using this material as a mechanical actuator.