Ionic correlations at the nanoscale: inversion of selectivity in a bio-nanochannel

TL;DR

This study combines simulation and theory to show that electrostatic correlations of multivalent ions can reverse the selectivity of a biological nanochannel, explaining experimentally observed phenomena.

Contribution

It introduces a physical mechanism for selectivity inversion in bio-nanochannels caused by multivalent ion correlations, supported by simulation and theoretical analysis.

Findings

Electrostatic correlations can invert nanochannel selectivity.

The phenomenon explains experimental observations in bacterial porins.

Differences and similarities with other electrokinetic effects are discussed.

Abstract

Here we show, combining a simulation and theoretical study, that electrostatic correlations typical of multivalent ions can reverse the selectivity of a biological nanochannel. Our results provide a physical mechanism for a new, experimentally observed phenomenon, namely the inversion of the selectivity of a bacterial porin (the E. Coli OmpF) in presence of divalent and trivalent cations. Also, the differences and similarities between the driving force for this phenomenon and other similar nano and micro-escale electrokinetic effects (e.g. inversion of streaming current in silica nanochannels) are explored.