Hofmeister Effect Matters in Nanopore Stoichiometry

The Hofmeister effect happens at interfaces of chemistry, physics and biology systems, especially referring to the influence of different ions on regulating protein structures and functions via a changing series of interactions and the structures between ions and water molecules. This study investigated the Hofmeister effect in nanopore stoichiometry by electrically characterizing the performance of an anthrax protective antigen protein nanopore under 15 chaotropic salt conditions. The results demonstrated efficient regulation of the electrical properties (e.g., discrete constant, opening current strength, signal-to-noise ratio, channel occlusion) by chaotropic salts, exhibiting either a cation- or anion-dominated Hofmeister effect in chaotrope or kosmotrope orders. In addition, the Hofmeister effect stabilized anthrax nanopores and enabled precise discrimination of single amino acids, glycans, and polymers at the single-molecule level. This discovery advances the field of nanopore stoichiometry and provides inspiration for the development of biomimetic ion-responsive sensors.