Regensburg 2016 – scientific programme

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SYAD: Symposium Anomalous Diffusion in Complex Environments

SYAD 3: BP Focus Session: Anomalous Diffusion in Complex Environments

SYAD 3.4: Talk

Thursday, March 10, 2016, 12:15–12:30, H45

The Power Spectrum of Ionic Nanopore Currents: The Role of Ion Correlations — •mira zorkot, Ramin Golestanian, and Douwe Jan Bonthuis — Rudolf Peierls Centre for Theoretical Physics, Oxford University, Oxford, OX13NP, United Kingdom

Measuring the ionic current passing through a nanometer-scale membrane pore has emerged over the past decades as a versatile technique to study molecular transport. These measurements su*er from high noise levels that typically exhibit a power law dependence on the frequency. A thorough theoretical understanding of the power spectrum is essential for the optimisation of experimental setups and for the use of measurement noise as a novel probe of the nanopores microscopic properties.

We calculate the power spectrum of electric-*field-driven ion transport through nanopores using both linearized mean-fi*eld theory and Langevin dynamics simulations. With only one *tting parameter, the linearized mean-*field theory accurately captures the dependence of the simulated power spectrum on the pore radius and the applied electric *field. Remarkably, the linearized mean-*field theory predicts a plateau in the power spectrum at low frequency f, which is con*rmed by the simulations at low ion concentration. At high ion concentration, however, the power spectrum follows a power law that is reminiscent of the 1/f dependence found experimentally at low frequency. Based on simulations with and without ion-ion interactions, we attribute the low-frequency power law dependdence to ion-ion correlations.