Chirality Unlocks Sub-Terahertz Molecular Dynamics In Peptide Nanotubes.

Low-frequency modes in the picosecond range play a key role in molecular recognition and biomolecular function. Here, we investigate how these dynamics at the interfaces of self-assembled peptide biomaterials relate to fine structural details of the supramolecular assembly. We resolve terahertz and mid-infrared modes in individual diphenylalanine nanotubes by nanoscale microspectroscopy, uncovering a direct correlation between supramolecular chirality, molecular arrangement, and picosecond dynamics at the nanotube-environment boundary. By combining THz and mid-IR nanoscopy with a multiscale strategy spanning single nanotubes and bulk measurements, supported by density functional theory calculations, we access the intrinsic picosecond response of peptide assemblies beyond the limits of conventional microscopy and ensemble averaging. Heterochiral (D-L) nanotubes display sharp resonances, whereas homochiral (L-L) nanotubes exhibit a comparatively featureless sub-THz profile, revealing a clear chirality-dependent contrast. Mode assignments show that the heterochiral features are dominated by localized torsional and bending motions of phenyl rings relative to the peptide backbone. Overall, chirality-dependent THz fingerprints emerge as sensitive descriptors of peptide nanotube architecture, while low-frequency nanospectroscopy provides a route to interrogate biomaterial interfaces under biologically relevant conditions.