Influence of effective polarization on ion and water interactions within a biomimetic nanopore

Biophys J. 2022 May 7:S0006-3495(22)00373-3. doi: 10.1016/j.bpj.2022.05.006. Online ahead of print.ABSTRACTInteractions between ions and water at hydrophobic interfaces within ion channels and nanopores are suggested to play a key role in the movement of ions across biological membranes. Previous molecular dynamics (MD) simulations have shown that anion affinity for aqueous/hydrophobic interfaces can be markedly influenced by including polarization effects through an electronic continuum correction (ECC). Here, we designed a model biomimetic nanopore to imitate the polar pore openings and hydrophobic gating regions found in pentameric ligand-gated ion channels. MD simulations were then performed using both a non-polarizable force field and the ECC method to investigate the behavior of water, Na+ and Cl⁻ ions confined within the hydrophobic region of the nanopore. Number density distributions revealed preferential Cl⁻ adsorption to the hydrophobic pore walls, with this interfacial layer largely devoid of Na+. Free energy profiles for Na+ and Cl⁻ permeating the pore also display an energy barrier reduction associated with the localization of Cl⁻ to this hydrophobic interface, and the hydration number profiles reflect a corresponding reduction in the first hydration shell of Cl⁻. Crucially, these ion effects were only observed through inclusion of effective polarization which therefore suggests that polarizability may be essential for an accurate description for the be...
Source: Biophysical Journal - Category: Physics Authors: Source Type: research