Single-Molecule Electrophoresis of β-Hairpin Peptides by Electrical Recordings and Langevin Dynamics Simulations

We used single-channel electrical recordings and Langevin molecular dynamics simulations to explore the electrophoretic translocation of various β-hairpin peptides across the staphylococcal α-hemolysin (αHL) protein pore at single-molecule resolution. The β-hairpin peptides, which varied in their folding properties, corresponded to the C terminal residues of the B1 domain of protein G. The translocation time was strongly dependent on the electric force and was correlated with the folding features of the β-hairpin peptides. Highly unfolded peptides entered the pore in an extended conformation, resulting in fast single-file translocation events. In contrast, the translocation of the folded β-hairpin peptides occurred more slowly. In this case, the β-hairpin peptides traversed the αHL pore in a misfolded or fully folded conformation. This study demonstrates that the interaction between a polypeptide and a β-barrel protein pore is dependent on the folding features of the polypeptide.