Coherence in stable microtubules

Danko Georgiev, School of Medical Science, Kanazawa University

Neuroquantology, December 2009, vol. 7, 4, pp. 538-47

Stable microtubules comprise a large proportion of neurons, and are the main component of the cytoskeleton, which supports the extended dendritic arborisation and the axons of the neurons. Most neuron microtubules are stabilised by the cross-linking of microtubule associated proteins (MAPs), and the capping of the ends of proteins, both of which suppress frequent assembly and disassembly of the microtubules. This greater stability in neuron microtubules answers the often asked question, as to why non-brain microtubules are not seen as a basis of consciousness. But this does not prevent the non-consciousness of microtubules outside the brain being trundled out as an argument against quantum consciousness.

In dendrites, cross-linking is performed by MAP2 and in axons by MAP-tau. The author argues that the GDP and GTP molecules are not able to provide energy for computation within the microtubule, and energy from their processes is argued to go into the microtubule wall, as a result of the stretching of pre-existing bonds between the tubulin dimer subcomponents in the microtubule lattice. The microtubules are composed of 13 protofilaments. The tubulin subcomponents or dimers are connected by longitudinal bonds within the same protofilament and lateral bonds between dimers in different protofilaments. Here, chemical energy has been transduced into stored elastic energy. The author considers that this stored elastic energy might be important for the microtubular functioning within cells. He suggests that microtubular computation might be driven by interaction between the electric field inside neurons and the charged elastic brain microtubules.

Reference:

Caplow, M. et al – Free energy stored in the microtubule lattice – Journal of Cell Biology, 127, pp. 1918-24

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