Nanotechnology-Enabled Sensors

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7.4 Proteins in Nanotechnology Enabled Sensors 427
instead of NAD co-factor. Reprinted with permission from the Elsevier
121
publications.
7.4.9 Motor Proteins in Sensing Applications
Motor proteins are interesting tools in nanotechnology. Apart from the
enzyme regulation and the cell signaling, they also play an important role
in moving molecules in cells. They generate the force which is responsible
for movements in cells and muscle contractions. Examples are activities
such as the movement of organelles along the molecular tracks in a cell,
enzymes along a DNA strand, and moving chromosomes during mitosis
(the division of molecules in eukaryotic cells). Plenty of applications are
emerging for such proteins in the field of sensing. In an interesting work,
Oliver et al have shown that the electromotility of the outer cells of the
mammalian cochlea can be mediated by a voltage-sensitive motor molecule
for cochlear amplification. 122 These proteins can also be associated
with microtubules, contributing to the sensory mechanism that activates
the checkpoints for bio-events that are completed in the correct order. 123
The motor proteins’ movements use energy from other sources. Without
a foreign energy provider the protein only moves randomly. In order to
make a movement in one direction, one of the movement steps should be
irreversible. Many motor proteins use the hydrolysis of an ATP molecule
which is bound to the protein. When the ATP is hydrolyzed, it releases a
phosphate and ADP. Many motor proteins generate movement in this way.
Myosin, which is a muscle motor protein, can run along the actin filaments
to generate muscle contraction.
Kinesin (Fig. 7.48) is involved in the chromosomes movements during
mitosis. Some of these proteins which are involved in the replication of
DNA, can move themselves along DNA strands at a rate of 1000 nucleotides
per second which is a phenomenal rate.