Proton-Driven Anthrax Protective Antigen Nanopore for Enantiospecific Discrimination of Chiral Amino Acids via Current Readout

Abstract

The anthrax protective antigen forms a heptameric transmembrane channel under acidic conditions and serves as a biological nanopore. Its use in nanopore sensing is limited by stability and signal quality under conventional electrolytes containing potassium or sodium ions. A stable anthrax protective antigen nanopore was constructed using a pH-asymmetric organic ionic liquid electrolyte, operated under a proton-driven gating mechanism. The resulting nanopore was evaluated for electrochemical performance, chemical stability, and capacity to distinguish levorotatory and dextrorotatory amino acid enantiomers. The system operated without the need for enzymes, chemical reactions, or machine-learning algorithms. The anthrax nanopore exhibited a single-channel open current of-approximately 5 pA, whereas commonly used protein nanopores display current amplitudes of tens to hundreds of picoamperes. This architecture provides a basis for chiral molecule identification via direct nanopore current readout.