Selective transport of plasma-derived reactive species through the plant aquaporin channels: a molecular dynamics study.

The selective permeability of reactive oxygen and nitrogen species (RONS), generated by cold atmospheric plasma (CAP), through plant aquaporins was investigated to identify plasma-derived species capable of intracellular delivery. Using atomistic molecular dynamics and enhanced sampling methods, we quantified the free energy profiles of eight RONS (HNO3, HO2, cis-HNO2, trans-HNO2, N2O4, NO, NO2, and O3) across the PIP2;1 aquaporin channel embedded in a lipid bilayer. Permeation was found to be controlled by two complementary features: the free-energy barrier opposing entry at the aromatic/arginine (ar/R) constriction, and the depth of the free-energy minimum within the pore interior. The strongly polar, hydrogen-bonding species HNO3 exhibited the highest entry barrier (≈ 16 kJ·mol- 1) and is thus the least permeable, whereas weakly polar species such as NO crossed the channel with minimal resistance. Notably, several species, most strikingly N2O4, combined facile entry with deep internal minima, indicating that they are readily admitted into the pore but strongly retained within it rather than freely transported. These results show that RONS selectivity in PIP2;1 is governed by molecular size, polarity, and hydrogen-bonding capacity, and provide a mechanistic basis for the rational selection of CAP-generated species in sustainable plasma-based agricultural technologies.