Ferroelectric behavior in microtubule dipole lattices: Implications for information processing, signaling and assembly/disassembly

Cytoskeletal microtubules structurally organize interiors of living eukaryotic cells. As polymers of subunit proteins (“tubulin”), which are each dipoles, microtubules are thus lattices of oriented dipoles. In general, three types of arrangements of dipoles in lattices may occur: (i) random, (ii) ferroelectric (parallel-aligned) and (iii) an intermediate weakly ferroelectric phase, which is length-dependent. Because of involvement in dynamical cell activities (movement, growth, mitosis, differentiation, etc.), models of microtubule signaling and information processing have been proposed. In these, tubulin units are assumed to represent informational “bit states” and to be coupled to intra-tubulin dipoles. In the present paper, we consider microtubules as lattice arrays of coupled local dipole states that interact with their immediate neighbors. Depending on the values of assumed model parameters, the system may exhibit “frustration”: conflict in satisfying all dipole couplings. Such systems have properties suitable for efficient information processing and computation. By slightly altering temperature and external field (both within physiological conditions), microtubule dipole lattices may assume a ferroelectric phase with long-range order and alignment with capabilities to propagate kink-like excitations. The ferroelectric phase appears to be optimal for microtubule signaling and assembly/disassembly. Microtubules may organize cell activities by operating in different modes suitable for information processing and computation (intermediate phase) or signaling and assembly/disassembly (ferroelectric phase).