Engendering Materials Directing Peptides with Non-Native Functionalities through Synthetic Sequence Modifications

Recent efforts in bioinspired Au nanomaterial synthesis have identified that Trp residues of Au binding peptides AuBP1 (WAGAKRLVLRRE) and AuBP2 (WALRRSIRRQSY) have the capacity to drive metal ion reduction. Such a capability could be intrinsically valuable for material production under sustainable conditions that limit the number of reagents required for nanoparticle generation. Additionally, it could also allow for precise localization of inorganic materials based upon peptide positioning. These advances in material peptide design could prove to be significant for applications in catalysis, sensing, plasmonic, etc. Herein, we examine this reduction capability of tryptophan-modified peptides to identify strategies to incorporate such reactivity into nonreactive peptides to enhance their individual functionality for material production. This is examined using peptide mutation studies that incorporate Au³⁺ reductive Trp residues into nonreactive materials binding peptides. The results demonstrate that reactivity can be incorporated into nonfunctional biomolecules where the location of the Trp, the neighboring residues in direct contact with the Trp, and the complete sequence all can be tuned to greatly modulated Au³⁺ reduction reactivity. Additionally, the binding strength of the peptide to the free metal ions in solution is shown to alter the reactivity where stronger affinity between the biomolecules and metal ions leads to diminished reduction. Taken together, these results present pathways toward selective biological modifications of material directing peptides to increase their inherent capabilities for the design, production, and stabilization of functional inorganic nanomaterials.