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Scaling Behavior of Ionic Transport in Membrane Nanochannels.

ABSTRACT: Ionic conductance in membrane channels exhibits a power-law dependence on electrolyte concentration ( G ? c?). The many scaling exponents, ?, reported in the literature usually require detailed interpretations concerning each particular system under study. Here, we critically evaluate the predictive power of scaling exponents by analyzing conductance measurements in four biological channels with contrasting architectures. We show that scaling behavior depends on several interconnected effects whose contributions change with concentration so that the use of oversimplified models missing critical factors could be misleading. In fact, the presence of interfacial effects could give rise to an apparent universal scaling that hides the channel distinctive features. We complement our study with 3D structure-based Poisson-Nernst-Planck (PNP) calculations, giving results in line with experiments and validating scaling arguments. Our findings not only provide a unified framework for the study of ion transport in confined geometries but also highlight that scaling arguments are powerful and simple tools with which to offer a comprehensive perspective of complex systems, especially those in which the actual structure is unknown.

SUBMITTER: Queralt-Martin M

PROVIDER: S-EPMC6242701 | biostudies-literature | 2018 Oct

REPOSITORIES: biostudies-literature

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Scaling Behavior of Ionic Transport in Membrane Nanochannels.

Queralt-Martín María M López M Lidón ML Aguilella-Arzo Marcel M Aguilella Vicente M VM Alcaraz Antonio A

Nano letters 20180910 10

Ionic conductance in membrane channels exhibits a power-law dependence on electrolyte concentration ( G ∼ c<sup>α</sup>). The many scaling exponents, α, reported in the literature usually require detailed interpretations concerning each particular system under study. Here, we critically evaluate the predictive power of scaling exponents by analyzing conductance measurements in four biological channels with contrasting architectures. We show that scaling behavior depends on several interconnected ...[more]

PMID: 30178677

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Project description:The electrokinetic behavior of molecules in nanochannels (<100?nm in length) have generated interest due to the unique transport properties observed that are not seen in microscale channels. These nanoscale dependent transport properties include transverse electromigration arising from partial electrical double layer overlap, enhanced solute/wall interactions due to the small channel diameter, and field-dependent intermittent motion produced by surface roughness. In this study, the electrokinetic transport properties of deoxynucleotide monophosphates (dNMPs) were investigated, including the effects of electric field strength, surface effects, and composition of the carrier electrolyte (ionic concentration and pH). The dNMPs were labeled with a fluorescent reporter (ATTO 532) to allow tracking of the electrokinetic transport of the dNMPs through a thermoplastic nanochannel fabricated via nanoimprinting (110?nm?×?110?nm, width?×?depth, and 100??m in length). We discovered that the transport properties in plastic nanochannels of the dye-labeled dNMPs produced differences in their apparent mobilities that were not seen using microscale columns. We built histograms for each dNMP from their apparent mobilities under different operating conditions and fit the histograms to Gaussian functions from which the separation resolution could be deduced as a metric to gage the ability to identify the molecule based on their apparent mobility. We found that the resolution ranged from 0.73 to 2.13?at pH?=?8.3. Changing the carrier electrolyte pH?>?10 significantly improved separation resolution (0.80-4.84) and reduced the standard deviation in the Gaussian fit to the apparent mobilities. At low buffer concentrations, decreases in separation resolution and increased standard deviations in Gaussian fits to the apparent mobilities of dNMPs were observed due to the increased thickness of the electric double layer leading to a partial parabolic flow profile. The results secured for the dNMPs in thermoplastic nanochannels revealed a high identification efficiency (>99%) in most cases for the dNMPs due to differences in their apparent mobilities when using nanochannels, which could not be achieved using microscale columns.

Dataset Information

Scaling Behavior of Ionic Transport in Membrane Nanochannels.

Publications

Scaling Behavior of Ionic Transport in Membrane Nanochannels.

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