Scientists watch on the atomic level how
individual molecules recognize each other.
The body is an almost perfect machine. For it to
function properly, each individual component, that is each molecule,
must reliably fulfill its specific function. Each molecule must thus "recognize"
other molecules and work with them. A team of researchers from the Max
Planck Institute for Solid State Research in Stuttgart, the Fraunhofer
Institute in Freiburg, and King's College in London, has now
successfully filmed pairs of molecules during the recognition process.
As reported to the journal Angewandte Chemie, the shapes of the
molecules change to accommodate each other.
Like humans, molecules also "greet" each other with
a kind of "handshake". Anyone who has tried to shake someone's right
hand with his or her own left will have had a little trouble: the
right and left hands do not fit together. In the same way, some
molecules that exist in both a right-handed (D) and left-handed (L)
configuration can tell if others they encounter are the D or L form.
Magali Lingenfelder and colleagues at the Max
Planck Institute for Solid State Research have now been able to use
scanning tunneling microscopy to take a series of pictures that follow
in detail the "encounters" of diphenylalanine molecules adsorbed onto
a substrate. (Diphenylalanine is the central structural unit within
polypeptide fibers found in the brains of Alzheimer's patients.) The
"film sequences" reveal that only molecules with the same chirality (handedness)
readily aggregate into pairs and chains.
Just as in a handshake, it is not enough that the
right hands hold each other. To grip each other firmly, the two hands
must adapt to fit their shapes together. Molecules do the same: close
examination of the "film", in conjunction with theoretical
calculations by researchers from King's College, prove that this type
of dynamic accommodation of shape also occurs when two molecules "shake
hands".
"Our work finally demonstrates that Linus Pauling
was right with his theory of intermolecular conformation of over 50
years ago," says Lingenfelder. "In molecular recognition, it is not so
much the static forms that are important, but rather how well the
molecules can conform to each other."
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