Ion channel coherence

A quantum mechanical description of ion motion within the confining potentials of voltage gated ion channels

Johann Summhammer, Valid Salari, Gustav Bernroider

Atom Institute – Vienna University, Kerman Neuroscience Research Centre & University of Salzburg

Journal of Integrative Neuroscience 11 (2) June 2012

Introduction

The authors argue that quantum oscillatory effects in the membrane ion channels of neurons may play a key role in neuronal signalling. Bernroider has not repeated an earlier discussion of the possible connection of such processing with consciousness, perhaps because of the unreasoning hostility that this arouses in certain quarters. However, in respect of biological research, the suggestion of functionally effective biological coherence, resonates with the discoveries of this coherence in photosynthetic organisms in recent years.
Advances in atomic-scale biological chemistry indicate that channel proteins, such as ion channels in neuron membranes may provide a quantum coherent environment even at high temperatures. The authors have studied the interaction between potassium ions in ion channels and surrounding carbonyl dipoles. Ion channels are proteins inserted through neuron cell membranes. The inward and outward flow of ions is basic to the passage of neural signals.

The ion channel protein has several components. The pore domain gate controls the access of ions into the proteins. A cavity inside this holds an ion before it is admitted to the filter; this area can hold a hydrated ion, meaning an ion that has attracted water molecules, before the ion’s entry into the protein’s selectivity filter, which holds at least two ions. The selectivity filter is described as an array of carbon/oxygen dipoles that are the backbone of carbonyl group in an amino acid sequence. Each filter segment has five dipoles. When one ion is taken up from the cavity into the filter, another is released from the selectivity filter either into the interior of the cell or outwards from the cell. The selectivity filter is responsible for conducting ions across the membrane. The authors refer particularly to the work of the MacKinnon group on the ability to combine selectivity of ions with a high rate of conductance across the membrane.

The essential question was how selectivity could be maintained without compromising conductance. The interaction between ions, attracted water molecules and neighbouring oxygen atoms is considered to require a quantum description. This raises the question of whether quantum effects can propagate in the classical states of proteins. The access of ions to the pore gate is a realtively slow process not likely to require quantum processing.

However, the selectivity filter can change its conformation from permissive to non-permissive on a much shorter timescale. It appears that in the conditions of the selectivity filter the ion’s wave function can become highly delocalised over a significant part of the filter region. This in turn exerts a non-classical influence on the carbonyl lining of the filter. The external cavity region and the selectivity filter are thought to be coordinated, and this may effect the conformation of the entire protein. The ions in this environment do not conserve their energy, but give off their energy in part to the vibration of the carbonyl dipoles. The authors have demonstrated that the oscillation frequency of the carbonyl dipoles can discriminate the energy minima of sodium ions from potassium ions, thus giverning the selectivity of the filter.

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