An
Oxford University physicist sees the future of nanotechnology
in the workings of one of Nature's tiniest motors,
that which allows some bacteria to swim by rotating
slender filaments known as flagella.
'The bacterial flagellar
motor is an example of
finished bio-nanotechnology,
and understanding how it
works and assembles is
one of the first steps
towards making man-made
machines on the same tiny
scale,' said Dr Richard
Berry, a Tutorial Fellow
in Physics at Oxford University.
'The smallest man-made
rotary motors so far are
thousands of times bigger.'
This motor has the same
power-to-weight ratio as
an internal combustion
engine, spins at up to
100,000 rpm and achieves
near-perfect efficiency.
Yet at only 50 nanometres
across, one hundred million
would fit onto a full-stop.
The only other natural
rotary electric motor is
in the enzyme ATP-synthase.
Dr Berry is a member of
the Rotary Molecular Motors
Group in the Oxford Department
of Physics. He presented
his research at the Biophysical
Society's Annual Meeting
in Salt Lake City, Utah,
on Sunday 19 February.
The physicist and his
Japanese colleagues changed
the proteins normally found
in the motor of E Coli
to make it run on sodium
instead of hydrogen ions.
This allowed them to reduce
its speed of rotation by
lowering the level of sodium
ions present. They also
made the actions of the
motor more easily detectable
by attaching tiny beads
to stubs of flagella. Ultimately
26 distinct steps could
be observed in each of
its revolutions.
'The motor runs on electric
current, the flow of hydrogen
or sodium ions across the
cell membrane, and each
step may be caused by one
or two sodium ions passing
through the motor,' explained
Dr Berry.
The tools involved included
optical tweezers, which
employ light beams to hold
and to measure transparent
particles, and a high-speed
fluorescence microscope
which can capture 2500
images per second.
Dr Berry and his colleagues
have so far determined
the torque-speed relationship
of the motor, and that
it can have up to twelve
independent 'cylinders.'
'Our research will allow
us to measure the performance
of the motor when we vary
things like the driving
voltage and number of cylinders,
and to understand the physics
of the fundamental torque-generating
process,' said Dr Berry.
Picture: Artist's impression
of the bacterial flagellar
motor. Credit: Akihiko
Ishijima.
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