Dehydration and ionic conductance quantization in nanopores

TL;DR

This paper explores ionic conductance quantization in nanopores, revealing how dehydration influences ion transport and proposing a method to probe microscopic ionic behaviors relevant to biological and synthetic systems.

Contribution

It predicts and analyzes quantized ionic conductance as a function of pore radius, highlighting the role of hydration shells and ion valency in nanoscale ionic transport.

Findings

Ion type minimally affects conductance steps

Higher valency ions show more pronounced conductance drops

Measurement of conductance quantization can reveal nanoscale dehydration effects

Abstract

There has been tremendous experimental progress in the last decade in identifying the structure and function of biological pores (ion channels) and fabricating synthetic pores. Despite this progress, many questions still remain about the mechanisms and universal features of ionic transport in these systems. In this paper, we examine the use of nanopores to probe ion transport and to construct functional nanoscale devices. Specifically, we focus on the newly predicted phenomenon of quantized ionic conductance in nanopores as a function of the effective pore radius - a prediction that yields a particularly transparent way to probe the contribution of dehydration to ionic transport. We study the role of ionic species in the formation of hydration layers inside and outside of pores. We find that the ion type plays only a minor role in the radial positions of the predicted steps in the ion conductance. However, ions with higher valency form stronger hydration shells, and thus, provide even more pronounced, and therefore, more easily detected, drops in the ionic current. Measuring this phenomenon directly, or from the resulting noise, with synthetic nanopores would provide evidence of the deviation from macroscopic (continuum) dielectric behavior due to microscopic features at the nanoscale and may shed light on the behavior of ions in more complex biological channels.