EM fields in microtubules
Danko Georgiev, Medical University of Varna
In this paper, Georgiev argues that any link between signals in the cortex and the microtubules has to be understood in terms of the local electromagnetic field. He dismisses a number of theories as to how the microtubules might support information processing and/or consciousness. For instance, the magnetic fields inside neurons are stated to be too weak relative to the background noise of the Earth’s magnetic field to support information processing. Instead, he argues that attention needs to be focused on the electrical field, which is responsible for the signals passing along neuronal membranes via ion channels to synapses, and is seen as a necessary source of input into microtubules, if these are in fact involved in information processing or consciousness.
Evidence is claimed for the idea of a model based on structured water and positively charged ions. Magnetic resonance studies indicate that water in neurons is more structured than normal liquid water. A substantial part of the water in neurons is bound to various biomolecules. Much of the rest of the water is structured with high viscosity and dynamic correlations between individual molecules. Most of this structured water is around the cytoskeleton, and studies of this water have tended to indicate the presence of long-range dipolar ordering leading to internal electric fields or oscillations of electric fields.
It has been further suggested that structured water close to microtubules could generate solitons, a form of quanta propagating as solitary waves. The author suggests that this involves the C-termini tubulin ‘tails’ that project from the microtubules and are capable of multiple conformations. The properties of the tubulin tails are a function of the acidic aminoacid residues, which allows them to be highly flexible. Studies show that these tubulin tails interact with microtubule associated proteins. The carboxyl termini of the tubulin tails have been shown to undergo modifications when interacting with MAPs. The C-termini have also been shown to contain molecules (called chaperone molecules) that assist in the folding of protein, and in particular in ensuring that protein folds in the correct way rather than in a large number of other possible ways. A cycle of removal and restoration of a tyrosine residue from C-termini is a characteristic of stable axonal microtubules. Changes to protein side chains located near the C-termini appear to regulate the interaction between microtubules and MAPs. MAP proteins such as tau and kinesin bind most effectively with particular side chains. Differences in the binding of MAPs are suggested to modulate the function of microtubules.
Georgiev suggests that molecular studies allow the construction of models, by which microtubules can process electrical information. The C-termini are electrically charged and physically flexible and can undergo conformational changes, in response to changes in the vector of the electrical field. Solitons can transfer energy between the tubulin tails without dissipation. These solitons are suggested to be capable of directly effecting the scaffold of presynaptic proteins and the release of neurotransmitters from synapses.