Divergent Outcomes in Resilin-Like Peptide Cross-linking: Unexpected Photocatalytic Damage vs Enzymatic Success.

Highly elastomeric materials are routinely found in nature that are generated from enzymatic cross-linking of proteins such as resilin. This process can be recreated on the benchtop using conventional photocatalytic approaches, which can be highly efficient; however, due to the large size of the elastomer generated via protein cross-linking, confirmation of the final structure remains elusive. Herein, we explore photocatalytic cross-linking of smaller resilin-like peptides (RLPs), taken from the resilin protein, which do not precipitate upon cross-linking. Using a [Ru(bpy)3]2+-based photocatalytic process, significant peptide degradation was observed, which dominated the reaction. Alternatively, enzymatic cross-linking of the peptides was observed to generate the anticipated product. Similar studies were conducted on a larger peptide construct where both the photocatalytic and enzymatic cross-linking process generated elastomeric materials with differing morphologies. AFM-based analysis confirmed vastly different Young's moduli based upon the cross-linking strategy. Computational modeling was used to predict likely molecular-level structures and mechanical properties of the elastomer materials based on both the photocatalytic and enzymatic preparation processes, indicating that the case where the rate of cross-linking is greater than that of chain fragmentation is the more likely photocatalytic scenario, based on the trends in predicted Young's modulus.