Protein
Machine (04.24.03) - Scientists are looking for ways to use motor proteins
to repair injuries from inside your body.
BioBots
(05.22.03) - Nanotechnology promises to send incredibly tiny biomedical machines
to your body’s rescue, delivering drugs or making internal repairs.
Just how do these miniscule devices work?
Could the same sort of thing that causes mad cow disease actually do something
useful? As this ScienCentral News video reports, one scientist says this is
the kind of impossible dream that nanotechnology can make come true.
Learning from Nature
Protein
molecules are the basic components of life. They have so many functions
that many nanotechnologists are interested in harnessing them to make tiny
machines.
Inside the human body, proteins look like ribbons folded in certain ways. "In
order for proteins to function, they have to fold into just the right shape,"
explains Susan Lindquist,
biologist and director of the Whitehead Institute for Biomedical Research. "And
unfortunately, sometimes they can get that wrong. Misfolded proteins can be
very toxic in cells. They can actually set up a chain reaction that gradually
converts all the other proteins of that type in the cell to that same altered
form, and poisons their functioning."
A properly folded protein. image: Protein Data Bank, Rutgers University
Proteins that are folded the wrong way are called
prions, short for proteinaceous infectious particles. Inside
mammals' brain cells, some types of prions can alter cell structure and lead
to fatal illnesses such mad
cow disease in animals or Creutzfeldt-Jakob disease in people.
But Lindquist thought that this chain reaction of protein structural change
that makes some prions so dangerous might have some useful aspects. When proteins
undergo this chain reaction of misfolding, they also form extremely tough
fibers. "These tough fibers are probably one of the things that make
our nerve cells go wrong when prions get inside of our brains," says
Lindquist. "When proteins change their shape, they stick together really
tightly. This can create very long fibers that are very tough and potentially
could be used to build things, because they are very very small fibers—much,
much smaller than we can manufacture today."
An improperly folded prion. image: Protein Data Bank, Rutgers University
Lindquist, who teamed up with physicists at the University of Chicago, started with proteins she has worked
with for years: yeast prions, which, importantly, are harmless. In fact, in
yeast they can be helpful, allowing cells to grow in places where they otherwise
wouldn't survive. "The prion protein of mammals which causes devastating
neurodegenerative diseases is actually a very different protein than the yeast
protein," explains Lindquist. "It misfolds the same way, but the
yeast protein is not dangerous. So no one has to worry about eating bread
or drinking beer or wine. They're not going to get prion disease from yeast.
They're very safe to work with in the laboratory as well."
Lindquist's team redesigned the yeast prions so that they bond with gold particles,
and then coated the fiber strings with metal to create extremely tiny, tough
wires. "The idea was, 'Could we make a very, very tiny wire by taking
advantage of these very, very thin but very, very tough proteins as templates?'
And we found that the wires could conduct electricity. Our next step would
be to do something useful, such as connecting up one circuit with another."
Because proteins do so much inside the body, Lindquist hopes that her wires
might be the first step to building tiny machines—"some really
complicated devices that could do some amazing things."
Working with these yeast prions also could help Lindquist figure out why other
prions attack the brain. "We're working very hard," she says, "on
trying to see if we can use yeast as a living test tube to study these misfolding
events that take place in our brains and cause such havoc." This, to
Lindquist, would represent a satisfying partnership between nature and scientists
in different fields. "For about 20,000 years now, we have been domesticating
plants and animals, and it's about time we started domesticating molecules."
Lindquist says that right now, nanotechnology is beginning to make this possible
as more scientists collaborate to imitate nature: "Biologists, physicists,
chemists, material scientists are working together trying to create all kinds
of brand new materials by taking advantage of what nature's already provided."
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