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If realism in art is about representing form, then biology is chock full of
real art. For decades, scientists have probed some of the tiniest structures
of life's basic building blocks (such as DNA or proteins), rendering full-color
ball-and-stick models of them that fill the pages of journals and adorn the
trophy cases of biology departments everywhere. While these representations
reveal some of the most intricate molecular details of life, they often fall
short in depicting how a single molecule moves. Just as the perfect picture
of a horse cannot convey the fluidity of it gallop, so does a frozen picture
of DNA fail in describing its intricate dance. "These are wet, warm, squishy
things," says Adam Cohen of Harvard University. They jiggle, they flap,
they twist, they turn, and they randomly "walk" about.
Studying how a single molecule moves is hard, however, because of these very
motions. Like a horse, if you set a single molecule free, it will wander away.
You can tie it down, ensuring that it no longer wanders, but then you can't
necessarily observe how it moves. Now, thanks to a machine built by Adam Cohen
and his colleagues at Harvard, it may be possible to confine a single molecule
and study its motions at the same time.
The machine basically uses a variable electric field to trap a single molecule
under a microscope. It does this by tracking the molecule's motion and then
rapidly applying tiny electric pulses to counter this motion and zap the molecule
back into place. At the AVS 55th International Symposium & Exhibition, Cohen
will describe how he and his colleagues can use this machine to look at things
like virus particles or single pieces of DNA. Recently they made a movie by
capturing 60,000 high-speed frames of a DNA molecule dancing. The studies show
the nature of the molecule's internal forces, says Cohen, and these properties
give information about how DNA interacts in a biological setting.
Cohen's talk, "Trapping Single Molecules in Water at Room Temperature"
is at 8:20 a.m. on Monday, October 20, 2008, in Room 312 of the Hynes Convention
Center.
Abstract: http://www.avssymposium.org/paper.asp?abstractID=228.
Posted October 21st, 2008
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