ULTIMATE COMPUTING - Quantum Consciousness Studies

166 Models of Cytoskeletal Computing
gradion fields within microtubule surfaces as the neighborhood areas around
intermicrotubule MAP bridges. They further assumed five possible
conformational states for each dimer determined by inter-MT linkage sites and
their cooperative allosteric effects, as well as dimer binding by a number of
different native substrates or foreign molecules. The pattern of tubulin dimer
conformational states in a region of MT lattice “governed” by attachment of inter-
MT linkages (or other MAPs) is defined as a “gradion,” or conformational field
which includes about seventeen dimers. Consequently, 5 17 different gradion
patterns could exist if the conformation of each subunit were independent of all
others. Cooperativity and allosteric effects preclude independence, so the number
of possible MT “gradions” is somewhat less, but still substantial. Roth and Pihlaja
(1977) see formation of many “gradions” within axopod MT as a mechanism for
position determination and coding for connections. Applied to neuronal
cytoskeleton, such deterministic patterns would be generally useful for mental
processes in the brain and be a viable candidate for “grain of the engram.”
The gradion theory may be applied to any large field of allosteric particles.
Allosterism and cooperativity in membranes, cell junctions, and protein particles
in many cells could explain aspects of cooperative communication, however
microtubules appear especially well suited for information functions. The MT
gradion model of Roth, Pihlaja, and Shigenaka is an early specific theory of
information processing in protein assemblies in general, and microtubules in
particular.
8.2.7 Gyroscopic Centrioles/Bornens
French molecular biologist Michel Bornens (1979) has investigated cellular
mechanisms of organization and argues for a dynamic stability based on
organizational properties of centrioles and the cytoskeleton. Specifically, Bornens
proposes that centrioles are animated by rapid oscillatory rotation about their
longitudinal axis which results in a dynamic stability and inertia analogous to a
spinning top or gyroscope. Peripheral movements throughout the cell are
interconnected by the cytoskeleton, with the gyroscopic centrioles an inert point
of reference which provides cellular gravity. Centrioles and microtubule
organizing centers (MTOC) are the origin for the cell’s spatial coordinates and
cytoplasmic movement appears to occur relative to the MTOC. Bornens likens
movement in each cylinder to a stepwise electric motor in which the central
“cartwheel” (or “pinwheel”) is equivalent to an ATP-dynein “stator,” and the
centriolar wall the moving “rotor.” Continuous torque rotation of centrioles could
serve to propel them through cytoplasm, like an “Archimedes screw” (Record,
1986). Bornens also considers the possibility of “back and forth” oscillation with
utility for scanning the cell environment.
Reviewing Bornens’ gyroscopic centriole model, Albrecht-Buehler (1981)
questioned the high rate of rotation required for significant inertia. Albrecht-
Buehler calculated that centrioles would have to rotate at frequencies of 2.3
million revolutions per minute before their kinetic energy matches one kT (the
thermal energy of one molecular degree of freedom). Consequently, “much
greater rotational frequencies would be required before the centriole could
withstand the impact of thermally moving molecules around them and maintain
stable axial orientation” (Albrecht-Buelhler, 1981). Bornens responded by
suggesting a submicroscopic mechanism “allowing more independence of the
centriole with respect to surrounding material.” Factors which could support his
contention include ordered water coupled to centriolar oscillation, some unknown
property of the “pericentriolar material,” ionic charge layer, or even
superconductivity as suggested by Fröhlich and Del Giudice’s group (Chapter 6).