Dipole interactions in axonal microtubules as a mechanism of signal propagation

The microtubules (MTs) of nerve cells are stable relative to their counterparts in the rest of the body. This stability allows them to participate in cellular signaling processes. Each of the MT's subunits, dimers of tubulin protein, has an electric dipole moment that contributes to the overall polarity of the structure. We propose that the orientation of the individual dipoles may be flipped due to a conformational change of the tubulin dimer if energy is supplied through guanosine tri-phosphate hydrolysis or via physical interactions. Thus the MT lattice may be viewed as an electric dipole lattice with some overall polarization upon which signals, in the form of dipole patterns, may be propagated through dipole interactions that induce conformational changes. As a nerve impulse propagates along a neuron (nerve cell), the neuronal MTs are subjected to a large transient electric field that interacts with the MT lattices. Based on the recent conjecture of information processing and/or energy transport by MTs, we have used a Monte Carlo technique to model the interactions between the MT's subunits and to investigate the response of the lattice to nerve impulses. Our model of these interactions addresses the problem of thermal fluctuations in the dipole lattice and demonstrates how the nerve impulse may cause a signal to propagate along the MTs within the axon.