Origin of current blockades in nanopore translocation experiments

Area of Science:

• Nanopore science
• Computational biophysics
• Physical chemistry

Background:

• Ionic current measurements in nanopores are crucial for sensing applications.
• Understanding ion transport through nanopores with biomolecules like DNA is complex.
• Existing electrokinetic models face challenges in accurately predicting experimental observations.

Purpose of the Study:

• To investigate ionic current behavior in a model nanopore with and without DNA.
• To validate atomistic simulations against experimental data.
• To elucidate the mechanisms behind DNA-induced current modulation and limitations of mean-field models.

Main Methods:

• Atomistic molecular dynamics simulations.
• Analysis of ionic current and charge carrier density.
• Comparison with experimental data and mean-field electrokinetic models.

Main Results:

• Simulations precisely reproduced experimental ionic current data, including crossover salt concentration.
• Steric exclusion of charge carriers by DNA was ruled out; carrier density increased with DNA presence.
• Mean-field models failed to quantitatively predict the observed effects, highlighting the importance of molecular drag.

Conclusions:

• Atomistic simulations provide a reliable method for studying ion transport in nanopores with DNA.
• Molecular drag, arising from various interactions with DNA, significantly impacts ion flow and is not captured by current mean-field theories.
• This work advances the understanding of nanopore electrokinetics and informs the development of more accurate theoretical models.