Physical properties of voltage gated pores

TL;DR

This paper develops simplified active pore models for ion channels using statistical physics, capturing gating dynamics and ion concentration effects consistent with experimental data.

Contribution

It introduces minimal active pore models with Langevin dynamics, bridging molecular complexity and experimental observations.

Findings

Models replicate gating dynamics of Na and K channels

External ion concentration significantly influences gating behavior

Simulations align with experimental data on ion fluxes and fluctuations

Abstract

Experiments on single ionic channels have contributed to a large extent to our current view on the function of cell membrane. In these experiments the main observables are the physical quantities: ionic concentration, membrane electrostatic potential and ionic fluxes, all of them presenting large fluctuations. The classical theory of Goldman--Hodking--Katz assumes that an open channel can be well described by a physical pore where ions follow statistical physics. Nevertheless real molecular channels are active pores with open and close dynamical states. By skipping the molecular complexity of real channels, here we present the internal structure and calibration of two active pore models. These models present a minimum set of degrees of freedom, specifically ion positions and gate states, which follow Langevin equations constructed from an unique potential energy functional and by using standard rules of statistical physics. Numerical simulations of both models are implemented and the results show that they have dynamical properties very close to those observed in experiments of Na and K molecular channels. In particular a significant effect of the external ion concentration on gating dynamics is predicted, which is consistent with previous experimental observations. This approach can be extended to other channel types with more specific phenomenology.