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SOUTHERN Italy’s active volcanoes

mean that living in the region is not

for the risk-averse. Less well known,

though, is the threat from the sea.

Tsunamis occur around once a

century in the Mediterranean Sea.

In 1908, a magnitude 7 earthquake

created a tsunami that almost

destroyed the Italian cities of

Messina and Reggio Calabria.

Stefano Lorito of the National

Institute of Geophysics and

Vulcanology in Rome and his team

used historical data to estimate

earthquake risk for three different

fault zones in the Mediterranean

region, and simulated the tsunami

that would result from such a quake.

(Journal of Geophysical Research,

DOI: 10.1029/2007JB004943).

They found that a major rumble

in the quake-prone region off the

coast of Greece would trigger a

tsunami 5 metres high, which

would strike the south-east coasts

of Sicily and mainland Italy within

an hour. Meanwhile, waves as high

as 1.5 metres could be triggered by

earthquakes off north Africa and in

the Tyrrhenian Sea, north of Sicily.

Other countries could also be

vulnerable. “A comparable or even

greater threat exists for the coasts

of Tunisia, Libya, Egypt and

Greece,” says Lorito.

Mediterranean

tsunami coming?

JUST like twins recognising and

approaching each other through

a crowd at a party, identical

stretches of double-stranded

DNA will seek each other out.

Although we know that

single complementary strands

of DNA attract each other, such

attraction was unheard of in

zipped-up, double-stranded

DNA, which must “unzip”

itself before it can be copied

or repaired. The finding could

suggest a preparatory stage

in the mechanism by which

DNA repairs itself.

Alexei Kornyshev of Imperial

College London and his team

mixed together two distinct

variants of double-stranded DNA

in water. One was labelled with a

fluorescent green marker and the

other red. The team found that

over time the reds and greens

congregated with their own kind

(The Journal of Physical Chemistry

B, DOI: 10.1021/jp7112297).

The researchers think the

recognition results from

complementary electrostatic

attractions between identical

regions of the double helix. The

pairing balances negative charges

in the sugar “backbone” of one

helix exactly with positive charges

within the central “groove” of

the other helix. “Therefore, you’d

get a symmetry,” says Kornyshev.

And the longer the strand, the

stronger the attraction.

Kornyshev says the

phenomenon might explain

how identical DNA strands line

themselves up ready for repairs,

and for the shuffling that takes

place when genes from each

parent are mixed up during the

formation of eggs and sperm.

When it comes to double-stranded DNA, identicals attract

AN INTERNAL clock hidden in your skin

cells could reveal whether your body

clock is out of sync with your lifestyle.

Steven Brown of the University

of Zurich in Switzerland and his

colleagues knew that the brain’s

circadian clock causes a gene called

Bmal1 to be more active in peripheral

cells during the daytime. To find out

how closely matched this activity

was, they used a virus to equip skin

cells from 11 early-rising “larks” and

17 late-rising “owls” with a firefly

gene that would produce a visible

glow whenever Bmal1 was active.

“The result is light coming out of the

cell in a 24-hour rhythm,” says Brown.

By monitoring times when the

cells glowed, they demonstrated

that skin cells showed the same

sleep-wake patterns as those reported

in questionnaires by at least half the

donors. But there were discrepancies

too – most notably in three

individuals with seasonal affective

disorder, suggesting that skin biopsies

might be useful for diagnosing sleep

and circadian disorders (Proceedings

of the National Academy of Sciences,

DOI: 10.1073/pnas.0707772105).

“Knowing that skin clocks ‘tick’

in the same way as brain clocks

provides a nice tool to address

whether a person is likely to be

an early or late riser,” says Russell

Foster, a circadian rhythm specialist

at the University of Oxford. “It’s

remarkable that measures from the

skin allow predictions of brain-

driven behaviour.”

Skin tells the time of your body clock

COULD sterilising plastic bottles in hot

water do more harm than good? Scott

Belcher and his colleagues at the

University of Cincinnati in Ohio have

found that polycarbonate plastic

bottles release up to 55 times more

bisphenol A (BPA) after they’ve been

washed in boiling water.

BPA is found in many plastic food

and drink containers and has been

linked to breast and prostate cancer.

Because they are often reused, Belcher

wanted to test whether old containers

leached BPA into their contents faster

than new ones. His team filled new

and used polycarbonate plastic bottles

with water and kept them at room

temperature for a week. They found

that the rate of BPA release into the

water by new and used bottles was

an average of 0.49 nanograms an hour.

But when the team mimicked

sterilisation by filling the bottles with

boiling water and leaving them to cool,

they found that the average rate of

BPA release jumped to 18.67 nanograms

per hour. This continued even after

the bottles had cooled and been

rinsed out (Toxicology Letters, DOI:

10.1016/j.toxlet.2007.11.001).

While the levels of released BPA

fall within safe limits as currently

defined by the European Food Safety

Authority, Belcher suggests switching

to bottles made of high-density

polyethylene as a precaution.

Be careful which bottles you sterilise

www.newscientist.com 2 February 2008 | NewScientist | 15

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