"This raises the bar for =
biomolecular=20
modeling," says Dennis Salahub, U of C co-author of a =
paper=20
published in the journal Proceedings of the National =
Academy=20
of Sciences (PNAS).
"At a fundamental level, =
it is by=20
far the most detailed insight that has been obtained =
for the=20
dynamic role of water in this kind of electron =
transfer, or=20
for that matter any biochemical reaction." =
Electron=20
transfer between proteins is the cornerstone of =
biological=20
energy transfer. Every life-form uses this process to =
convert=20
food or sunlight into chemical energy.
The=20
interdisciplinary team of researchers found that the =
electron=20
travels over a bridge made of a water molecule, while =
residues=20
on one of the proteins form a sort of 'molecular =
breakwater'=20
to keep other water molecules away while the electron =
travels=20
across the bridge.
"You don't want too many =
(water=20
molecules around the bridge) because it gets too =
crowded and=20
they're all bumping into each other and you can't get =
one to=20
fit at just the right position and the right angle =
(for the=20
bridge) for any length of time," says PhD student and=20
co-author Nathan Babcock. "It's like being on a =
crowded subway=20
where you can't get comfortable."
In =
artificial=20
mutations with a faulty breakwater, the water bridge =
is=20
disrupted and the rate of electron transfer is =
markedly=20
reduced, he says.
Using the CHARMM molecular=20
simulation computer program, the research team =
examined a 40=20
nanosecond period of electronic coupling of the =
proteins=20
methylamine dehydrogenase and amicyanin from the =
bacterium=20
Paracoccus denitrificans.
"This is fundamental =
research but you can imagine how studies like this can =
be=20
applied to various genetically modified organisms, and =
if you=20
can gain control over some, you can use it to either =
speed up=20
or slow down a particular reaction," says Salahub. =
He=20
says the work was made possible with the collaboration =
of two=20
of the U of C's interdisciplinary research institutes; =
the=20
Institute for Biocomplexity and Informatics (IBI) and =
the=20
Institute for Quantum Information Science (IQIS).=20
Babcock, whose background is in quantum =
information=20
theory, was pleased to do research at the union of =
these two=20
disciplines.
"When you think of quantum =
mechanics,=20
usually you're thinking solid state semi conductors, =
atoms=20
trapped with lasers, etc. It's usually cold laboratory =
stuff,=20
not warm globby biological stuff," says the PhD =
student. "I=20
think the union of biology and quantum mechanics is =
very, very=20
exciting." =
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