Selectivity filter gate versus voltage-sensitive gate: A study of quantum probabilities in the Hodgkin-Huxley equation

TL;DR

This paper investigates the quantum effects in ion channel gates, comparing a semi-quantum model with the classical Hodgkin-Huxley model, and finds that the semi-quantum approach can enhance understanding of spike generation.

Contribution

It introduces a semi-quantum model of ion channel gating that aligns with and potentially improves upon the classical Hodgkin-Huxley model.

Findings

The semi-quantum Bernroider-Summhammer model agrees with the Hodgkin-Huxley model under various conditions.

Quantum effects may influence the selectivity filter gate in ion channels.

The semi-quantum model can refine classical descriptions of spike generation.

Abstract

The Hodgkin-Huxley (HH) model is a powerful model to explain different aspects of spike generation in excitable cells. However, the HH model was proposed in 1952 when the real structure of the ion channel was unknown. It is now common knowledge that in many ion-channel proteins the flow of ions through the pore is governed by a gate, comprising a so-called selectivity filter inside the ion channel, which can be controlled by electrical interactions. The selectivity filter is believed to be responsible for the selection and fast conduction of particular ions across the membrane of an excitable cell. Other (generally larger) parts of the molecule such as the pore-domain gate control the access of ions to the channel protein. In fact, two types of gates are considered here for ion channels: the external gate, which is the voltage sensitive gate, and the internal gate which is the selectivity filter gate (SFG). Some quantum effects are to expected in the SFG due to its small dimensions, which may play an important role in the operation of an ion channel. Here, we examine parameters in a generalized model of HH to see whether any parameter affects the spike generation. Our results indicate that the previously suggested semi-quantum-classical equation proposed by Bernroider and Summhammer (BS) agrees strongly with the HH equation under different conditions and may even provide a better explanation in some cases. We conclude that the BS model can refine the classical HH model substantially.