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Don't stop now: it's rush hour inside
your body. Every second of every moment, ions by the
billions are flooding in and out of your cells. These
mass migrations send waves of electric charge changes
coursing down your nerves, transmitting sensory signals
and muscle commands as fast as electricity can carry
them.
Ions arrive and depart from cells
almost instantaneously, streaming through the oily membrane
surrounding each cell as fast as if it weren't there.
But in reality, each charged atom must pass through
one of thousands of portals in the membrane known as
an ion channels, designed to allow a specific kind of
ion to enter. For example, channels for potassium must
prevent similar ions such as sodium--which are nearly
the same size as potassium atoms and carry an identical
positive charge--from squeezing through at the same
time. By rights, this filtering should slow your body's
business to a crawl. Just how ion channels can conduct
traffic so quickly and selectively baffled researchers
for years.
Now, biophysicists Benoit Roux and
Simon Berneche of Weill Medical College at Cornell University
have described mass ion migration in unprecedented detail.
With the help of Alliance supercomputers at NCSA, they
simulate the passage of ions through a potassium channel
at the atomic scale. The results offer scientists valuable
perspectives on how ion channels and other molecular
machines operate in every living cell. 
Access Online | Posted 10-22-2002
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