Many biomaterials are piezoelectric (i.e., mechanically deform under an applied electric field); however, the molecular origin of this phenomenon remains unclear. In the case of protein-based scaffolds, one possibility involves flexible response of local folding motifs to the applied field. Here, we test this hypothesis by examining the piezoresponse in a series of helical peptide-based oligomers. Control over folding propensity is exerted through systematic variation in both side-chain sequence and backbone composition. Piezoresponse is quantified by piezo-force microscopy on polar self-assembled monolayers. The results indicate backbone rigidity is an important determinant in peptide electromechanical responsiveness.

This work presents new results and summarizes literature results on the chiral induced spin selectivity (CISS) effect observed for amino acids, peptides, and DNA. To facilitate robust comparisons between measurements of different types and by different groups, we propose a convention for describing the spin-dependent properties of chiral materials and apply it in the discussion. Different phenomena known to affect the sign and magnitude of the spin polarization are described and critically analyzed, including: the molecule's orientation, the molecule's dipole moment direction with respect to the electron propagation direction, the molecular length, the molecule/substrate interface, and the role of the molecule's secondary structure. Lastly, we identify open key questions about spin-filtering by biomolecules at interfaces.

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We report a new methodology for the electromechanical characterization of organic monolayers based on the implementation of dual AC resonance tracking piezo force microscopy (DART-PFM) combined with a sweep of an applied DC field under a fixed AC field.