Discrimination of Oxytocin, a behavioral neuropeptide hormone, and its structural variants by nanopore

Oxytocin, a neurohormone peptide, is implicated in various physiological processes, such as functions related to social behavior, reproduction, and emotional regulation. Recently, this peptide has been identified as a potential biomarker of human psychiatric disorders. Until now, no analytical tool has been able to routinely detect oxytocin and its variants, which can have different effects on their receptor binding and activity. This work uses an aerolysin nanopore and two mutants to detect oxytocin (OXT) and oxytocin-free acid (OXT-FA) differing by a single amine group. Several oxytocin variants were used to understand the effect of structure and conformational changes of the peptides on the electric signal. We identify two conformations in native conditions, allowing their discrimination. Nanopore mutants showed improved discrimination of these peptides. Molecular dynamics simulation allowed us to rationalize the competition between electroosmosis and electrophoresis on OXT and OXT-FA transport through aerolysin. This work demonstrates the potential for analyzing conformational biomarkers for diagnostic purposes.