Scientists at the University of Toronto have
recorded atomic motions in real time, offering a glimpse into the very essence
of chemistry and biology at the atomic level.
Their
recording is a direct observation of a transition state in which atoms undergo chemical
transformation into new structures with new properties – in this case the
transfer of charge leading to metallic behaviour in organic molecules. It is
described in a study reported in the April 18 issue of Nature.
"It's
the first look at how chemistry and biology involve just a few key motions for
even the most complex systems," says U of T chemistry and physics
professor R. J. Dwayne Miller, principal investigator of the study. "There
is an enormous reduction in complexity at the defining point, the transition
state region, which makes chemical processes transferrable from one type of
molecule to another. This is how new drugs or materials are made."
Miller, who
holds a joint appointment as director of the Max Planck Research Group for
Structural Dynamics at the Centre for Free Electron Laser Science, conducted
the research with colleagues from institutions in Germany and Japan. He says
nature uses this reduction principle at transition states to breathe life into
otherwise inanimate matter.
"Imagine
the complexity of all the enormous number of possible arrangements of atoms in
DNA or any other biologically active molecule. It always does the same thing to
drive a biological function. We can now see how all these possible motions
become coerced along a particular pathway by a dominant player."
To help
illuminate what's going on here, Miller explains that with two atoms there is
only one possible coordinate or dimension for following the chemical pathway.
With three atoms, two dimensions are now needed. However, with a complex
molecule, it would be expected that hundreds or even thousands of dimensions
would be required to map all possible trajectories of the atoms.
"In
this case, chemistry would be a completely new problem for every
molecule," says Miller. "But somehow there is an enormous reduction
in dimensions to just a few motions, and we are now able to see exactly how
this works at the atomic level of detail."
The result
builds on a milestone Miller and some former graduate students first reached a
decade ago.
"One of
the longstanding dream experiments is to directly observe atomic motions during
the defining moments that lead to structure change, and we were able to watch
simple phase transitions at the atomic level back in 2003," says Miller. "This
led to a new understanding that now allows for minimally invasive laser
surgery. It's a testimony to the importance of basic science and never knowing
where new understandings will lead."
"The
first atomic movies were very grainy, much like the first motion
pictures," says Miller. "The new movies are so clear one could dare
say they are becoming beautiful to behold, especially when you remember you are
looking at atoms moving on the fly. We've captured them at an incredibly fast
rate of less than 1 millionth of a millionth of a second per frame."
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