The neuronal cytoskeleton
The neuronal cytoskeleton is protein lattice composed from microtubules,
intermediary and actin filaments. It was conjectured that the neuronal
microtubules are essential subneuronal processors of information i.e. they act as
quantum computers that’s why in this study we will focus our attention on the
interaction between the microtubules and the local electromagnetic field.
Microtubules are hollow cylindrical tubes, of about 25 nm in diameter on the
outside and 14 nm on the inside, whose walls are polymerized arrays of protein
subunits. Their lengths may range from tens of nanometers during early
assembly, to possible centimeters in nerve axons within large animals. The
protein subunits assemble in longitudinal strings called protofilaments, 13 parallel
protofilaments laterally align to form the hollow tubules. The protein subunits are
peanut shaped dimers, which in turn consists of two globular proteins, monomers
known as α- and β-tubulin.
The α- and β-tubulin monomers are similar molecules with identical orientation
within protofilaments and tubule walls. In the polymerized state of the MT, one
monomer consists of 40% α-helix, 31% β-sheet and 29% random coil. Each
monomer consists of about 500 aminoacids, is about 4nm x 4nm x 4nm and has
a local polarity. Each dimer, as well as each MT, appears to have an electric
polarity or dipole, with the negative end oriented towards the α-monomer and the
positive end towards the β-monomer. The dipole character of the dimer
originates from the 18 calcium ions bound within each β-monomer. An equal
number of negative charges required for the electrostatic balance are localized
near the neighboring α-monomer (Mavromatos et al., 2002).
12