Probing Voltage Dependence Interaction of Cationic Peptides with Bacterial Porins at A Single-Molecule Level

This study examined how cationic α‑helical antimicrobial peptides such as protamine exchange between the aqueous phase and the transmembrane β‑barrel porin OmpF (E. coli) at the single‑molecule level. High‑resolution conductance recordings in planar lipid bilayers revealed clear voltage‑ and concentration‑dependent ion current blockages, consistent with transient peptide interactions within the OmpF lumen. Peptide length influenced the characteristics of these interactions: longer protamine fragments produced weaker and less frequent blockages. At low transmembrane potentials, all peptides interacted weakly with the pore, whereas higher potentials increased the likelihood and duration of detectable events. These findings establish OmpF as a tractable system for probing cationic peptide-channel interactions and provide a descriptive framework for understanding how arginine‑rich peptides engage with β‑barrel pores due to likely electrostatic trapping, without implying specific transport pathways or translocation mechanisms.