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LONG-DISTANCE relationships really mess up your life, and they don鈥檛 do much
for your biochemistry either. We used to think communication between molecules
in solution was impossible unless they were almost close enough to bump into
each other. But in fact, a strand of DNA can provoke a reaction in another
strand far away鈥攁 finding that reveals biochemistry as fiendishly
complex.

Ions seem to act as the go-between, say Kenneth Breslauer from Rutgers
University in New Jersey and his colleagues at the University of Cape Town.

Breslauer鈥檚 team studied a strand of DNA that would fold up in an alkaline
solution (where there are hardly any hydrogen ions) and unfold in an acidic
solution, where hydrogen ions are plentiful. They dissolved these strands in an
alkaline solution along with another type of strand that repelled hydrogen ions.
The solution was so dilute that the strands were on average about 6000 angstroms
apart.

Until now, biochemists believed that molecules couldn鈥檛 communicate if they
were more that a few angstroms apart. But the team found that the folded strands
tended to unfold, despite the alkaline solution. They concluded that the
hydrogen-repelling strands were pushing hydrogen ions towards the folded strands
and increasing their local acidity. 鈥淵ou don鈥檛 need any kind of bond between
them, just a shared medium,鈥� he says.

Breslauer believes many biological molecules signal in this way, possibly
using calcium or other small ions such as hydrogen. 鈥淚t鈥檚 like a ship causing a
wave in the ocean which causes another ship to rock.鈥� If he鈥檚 right, it could
complicate matters for biologists: it would mean reactions could be influenced
by a huge number of molecules both near and far. 鈥淚t opens a real Pandora鈥檚
box,鈥� Breslauer says.

As an example, Breslauer cites transcription factors which switch on
particular genes by binding to part of an organism鈥檚 genome. Biologists assume
that their effect propagates along the DNA to related genes, but Breslauer says
a message could jump across to a completely different part of the genome via
ions in the solvent.

Dinshaw Patel, a biochemist at the Memorial Sloan-Kettering Cancer Center in
New York City, says Breslauer鈥檚 work is going to have an impact in his field.
鈥淚t makes us think differently,鈥� he says. 鈥淭he challenge is going to be finding
out how general this crosstalk is.鈥�

Breslauer calculates that once the culprit is removed, its influence would
quickly evaporate. This would mean the ions repelled by the second DNA strand in
the experiment would take just a few femtoseconds (million billionths of a
second) to diffuse back throughout the solution.

Hence this cannot explain the effect of homeopathy, which proponents suggest
works by molecules leaving some form of 鈥渕emory鈥� in water after they have been
diluted out.