By Michael Schirber (as reported on LiveScience.com)
posted: 05 February 2008 09:27 am ET
Scientists may one day be able to destroy
viruses in the same way that opera singers presumably shatter
wine glasses. New research mathematically determined the frequencies
at which simple viruses could be shaken to death.
"The capsid of a virus is something
like the shell of a turtle," said physicist Otto Sankey
of Arizona State University. "If the shell can be compromised
[by mechanical vibrations], the virus can be inactivated."
Recent experimental evidence has shown
that laser pulses tuned to the right frequency can kill certain
viruses. However, locating these so-called resonant frequencies
is a bit of trial and error.
"Experiments must just try a wide
variety of conditions and hope that conditions are found that
can lead to success," Sankey told LiveScience.
To expedite this search, Sankey and his
student Eric Dykeman have developed a way to calculate the
vibrational motion of every atom in a virus shell. From this,
they can determine the lowest resonant frequencies.
As an example of their technique, the
team modeled the satellite tobacco necrosis virus and found
this small virus resonates strongly around 60 Gigahertz (where
one Gigahertz is a billion cycles per second), as reported
in the Jan. 14 issue of Physical Review Letters.
All objects have resonant frequencies
at which they naturally oscillate. Pluck a guitar string and
it will vibrate at a resonant frequency.
But resonating can get out of control.
A famous example is the Tacoma Narrows Bridge, which warped
and finally collapsed in 1940 due to a wind that rocked the
bridge back and forth at one of its resonant frequencies.
Viruses are susceptible to the same kind
of mechanical excitation. An experimental group led by K.
T. Tsen from Arizona State University have recently shown
that pulses of laser light can induce destructive vibrations
in virus shells.
"The idea is that the time that the
pulse is on is about a quarter of a period of a vibration,"
Sankey said. "Like pushing a child on a swing from rest,
one impulsive push gets the virus shaking."
It is difficult to calculate what sort
of push will kill a virus, since there can be millions of
atoms in its shell structure. A direct computation of each
atom's movements would take several hundred thousand Gigabytes
of computer memory, Sankey explained.
He and Dykeman have found a method to
calculate the resonant frequencies with much less memory.
The team plans to use their technique
to study other, more complicated viruses. However, it is still
a long way from using this to neutralize the viruses in infected
people.
One challenge is that laser light cannot
penetrate the skin very deeply. But Sankey imagines that a
patient might be hooked up to a dialysis-like machine that
cycles blood through a tube where it can be hit with a laser.
Or perhaps, ultrasound can be used instead of lasers.
These treatments would presumably be safer
for patients than many antiviral drugs that can have terrible
side-effects. Normal cells should not be affected by the virus-killing
lasers or sound waves because they have resonant frequencies
much lower than those of viruses, Sankey said.
Moreover, it is unlikely that viruses
will develop resistance to mechanical shaking, as they do
to drugs.
"This is such a new field, and there
are so few experiments, that the science has not yet had sufficient
time to prove itself," Sankey said. "We remain hopeful
but remain skeptical at the same time."
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