The Role of Noise in Determining Selective Ionic Conduction Through Nano-Pores

Abstract

The problem of predicting selective transport of ions through nano-pores from their structure in the biological and nano-technological systems is addressed. We use a molecular dynamics simulation to provide insight into the key physical parameters of nano-pores and develop a self-consistent analytic theory describing ionic conduction and selectivity through these devices. We analyse the ion's dehydration and excess chemical potential, derive an expression for the conductivity of the nanopore, and emphasize the role of fluctuations in its performance. The theory is verified by comparison of the predicted currentvoltage characteristics with the molecular dynamics results and experimental data obtained for a graphene nano-pore and the KcsA biological channel.

Prehistory probability distribution of ion transition through graphene nanopore

“…One important mechanism of such coupling is the variation in the number and orientation of water molecules in the 1st and 2nd hydration shells of the permeating ion, in the presence of the EDL for nonzero Q f . In turn, this variation affects the height of the potential barrier separating the left (z > 0) and right electrolytes [6], [12] which is what controls ion current through the pore.…”

“…Similarly, N 1 is reduced from 6 to ∼3.8 in the pore for both values of Q f . This dehydration plays a major role in formation of the potential barrier impeding permeation events, cf [6], [12] The effect of the local EDL structure on the number of water molecules in the hydration shells is most clearly seen in the relaxation of these numbers back to their bulk values immediately after a transition event. For Q f = 0.75e the relaxation time is shorter than 50 ps for both shells.…”

“…e.g. the first hydration shell is often considered to be intact near a charged surface [5] even though it is known that dehydration and saturation of the water orientation have significant effects on the local [11] dielectric permittivity, the potential of the mean force [12], and, therefore, on the current through the pore.…”

The dynamics of quasiparticles in a toy model of the KcsA biological ion channel

“…It is also believed that the concept of quasiparticles can turn out useful in constructing a functionalised nanotubes with prescribed properties. The latter appears at the front end of the research towards efficient water desalination atomically thin membranes [23].…”

Origin and control of ionic hydration patterns in nanopores

“…We compare the analytically predicted patterns with the results of MD simulations for different ionic locations near graphene nanopores with a diversity of shapes, geometries and strains. The results are applicable to narrow biological channels [24,38,39], functionalized sub-nanopores [24,25,40,41], nanotubes [42] and nanoslits [16,34]. Thus, this work takes an important step towards controlling the function of nanoscale devices by tailoring the hydration patterns.…”