Deciphering the Roles of Interfacial Amino Acids in Inter-Protein Charge Transport

Elucidating charge transport (CT) through proteins is critical for gaining insights into ubiquitous CT chain reactions in biological systems and developing high-performance bioelectronic devices. While intra-protein CT has been extensively studied, crucial knowledge about inter-protein CT via interfacial amino acids is still absent due to the structural complexity. Herein, by loading cytochrome c (Cyt c) on well-defined peptide self-assembled monolayers to mimic the protein-protein interface, we provide a precisely controlled platform for identifying the roles of interfacial amino acids in solid-state CT via peptide-Cyt c junctions. The terminal amino acid of peptides serves as a fine-tuning factor for both the interfacial interaction between peptides and Cyt c and the immobilized Cyt c orientation, resulting in a nearly 10-fold difference in current through peptide-Cyt c junctions with varied asymmetry. This work provides a valuable platform for studying CT across proteins and contributes to the understanding of fundamental principles governing inter-protein CT.