ULTIMATE COMPUTING - Quantum Consciousness Studies

164 Models of Cytoskeletal Computing
researchers, Barnett scoured the subcellular biological realm in search of
molecular scale information processing concepts. His fancy was captured by
cytoskeletal microtubules and neurofilaments! He has proposed information
representation as patterns in the subunits of cytoskeletal polymer subunits. He
proposes that specific subunit states may be characterized by “electrons
transferred from delocalizable molecular orbitals,” but his basic premise would
also be supported by other causes of conformational state variability among MT
and neurofilament polymer subunits. Barnett suggests that filamentous
cytoskeletal structures operate like information strings analogous to word
processors.
In Barnett’s conceptualization (Figure 8.2), information strings move from
right to left along processing channels, which run parallel to one dimensional
memory channels in which character strings can be stored. Barnett’s string
transformers can perform global replacements on sequences of characters like
common word-processors. His model assumes the existence of processing
channels (MT) along which strings of information can move, and memory
channels (neurofilaments) which consist of a succession of locations, each of
which can hold a single character. Parallel array and lateral interconnectedness of
MT and neurofilaments could qualify these cytoskeletal elements as string
processors, assuming that information may be represented in the polymers.
Barnett’s model is thus compatible and complementary with other models of
conformational patterns within MT and the cytoskeleton.
8.2.6 Microtubule “Gradions”/Roth, Pihlaja, Shigenaka
Roth, Pihlaja, and Shigenaka (1970), and Roth and Pihlaja (1977) have
considered information processing in two types of biomolecular assemblies:
membrane rosettes and microtubules. Citing cooperative allosteric effects among
adjacent proteins or protein subunits, they propose that conformational gradients
in protein arrays represent information by patterns of conformational states
among near neighbors in protein lattices.
Rosettes are ordered rings which consist of from seven to twelve membrane
embedded proteins important in membrane fusion in lower organisms.
One example of rosette function is in “suctorian feeding”, in which certain
protozoa affix themselves to a host cell membrane and feast upon its cytoplasm
by sucking its contents through a rosette common to both membranes. Bardele
(1976) suggested that rosettes utilize concepts of cooperativity and allosterism
because the triggering of conformational dynamics within the complex does not
require contact with all particles. Stimuli at only one or a few subunits followed
by allosteric changes in the rest can cause activation of the total complex. Satir
(1973) showed that rosettes in membranes of tetrahymena have rosette pairs in
register with each other: internal and external rings of eight proteins each.
Induction of a conformational change by binding of an effector molecule at the
external rosette causes allosteric cooperative changes in the conformation and
functional states of all sixteen subunits. In mutants with aberrant rosettes, a
minimum of 5 subunits is required before rosettes functionally respond.
Roth, Pihlaja, and Shigenaka considered the next level of complexity in
protein assemblies to be exemplified by microtubules. They viewed MT as highly
oriented patterns of tubulin dimers and anticipated at least three different
conformational states of each tubulin dimer, based on studies of tubulin binding to
vinblastine and GTP (Luduena, Shooter, and Wilson, 1976). Biologists Roth,
Pihlaja, and Shigenaka (1970) studied the patterns of linkage among MT within
the axopod of a simple organism called Echinosphaerium, a complex spiral
assembly of hundreds of MT. The precisely patterned, interwoven spiral arrays of