Dielectric polarization, electrical conduction, information processing and quantum computation in microtubules. Are they plausible?

Abstract

The multitude and diversity of functions performed by the cytoskeleton of eukaryotic cells poses a major scientific puzzle. Microtubules, which are the main components of the cytoskeleton, are engaged in such important activities as material transport, cell motility, cell division, signal transduction and possibly information processing within axons of nerve cells. The latter aspect has been recently brought to the forefront of consciousness studies by R. Penrose and S. Hameroff. In this paper we discuss the potential of microtubules as information processing units from a physical standpoint. In particular, since electric dipoles are a characteristic property of protein molecules, and as such may undergo various ordering phase transitions, it can be expected that microtubules support the existence of various ferroelectrically ordered states. It is also argued that the piezoelectric effect may link electric and elastic properties of a dielectric polymer system and hence explain a number of experimental observations both in vitro and in vivo. Furthermore, preliminary results are shown of recent quantum mechanical calculations for the electrical conduction properties of microtubule protofilaments which support the assertion that the latter may function under certain conditions very much like semiconducting devices. Indirect evidence links the cytoskeleton with information processing and cognitive function. We discuss some plausible ways in which axonal microtubules can be involved in the functioning of the brain. Finally, we present a hierarchy of energy values for a number of physical and chemical interactions of interest and discuss their relative importance.

A critical assessment of the information processing capabilities of neuronal microtubules using coherent excitations

“…Assuming that all tubulin is polymerized in the MT cases and that there are uniform MT distributions with combinations of parallel and series networks of 10-μm-long MTs, a longitudinal MT resistance of 0.8 M /μm can be estimated [31]. This compares favorably to an earlier theoretical estimate based on a Hubbard model with electrons hopping between tubulin monomers [32,33] that predicts MT resistances to be 0.2 M /μm. Additionally, this finding is two orders of magnitude smaller than dry MTs, which is to be expected.…”

On the role of the plasmodial cytoskeleton in facilitating intelligent behavior in slime mold Physarum polycephalum

“…The forms of information it may transmit include electrical potential, mechanical force, quantum events, propagating waves of protein conformational changes, facilitated chemical transport and biochemical signal transduction cascades. 24,[26][27][28][29][30][31][32] The cytoskeleton therefore represents an attractive model for describing data transmission within cells, as all of these signaling events may be interpreted as data being fed into a cellular computer. We are by no means the first to suggest this, but such a topic has not been previously described in slime mold models.…”

Actin quantum automata: Communication and computation in molecular networks

“…Seeds are just two sets of three adjacent cells each, at positions (6,7,8) and (12,13,14). Cell 7 is initialised at 00010, cell 8 and 12 at 00100, cell 13 at 01000.…”

“…They are responsible for keeping a cell shape and implementing the cell's motility but also they play a role of the cell's nervous system: together with extracellular matrix [1] the intracellular networks of proteins process information and implement learning [2][3][4][5][6][7][8][9][10]. By modulating dendritic ion channel activity actin filaments determine rule of neural information processing and facilitate computational abilities of dendritic trees via facilitation of ionic condensation and ion cloud propagation [11].…”