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served up cold
By Rachel Ehrenberg
The hot spot for life on early Earth may
have been very cold. Tiny pockets that
form inside ice can contain and protect
replicating molecules, researchers report
September 21 in Nature Communications.
The paper suggests that life could have
sprung from icy slush covering a fresh-
water lake, rather than a boiling deep-sea
hydrothermal vent or the “warm little
pond” proposed by Charles Darwin. And
perhaps the frigid, icy surfaces of other
planets are not as barren as they appear,
proposes the research team from the
MRC Laboratory of Molecular Biology
in Cambridge, England.
Tiny tools could have medical uses
Enzyme-triggered devices could deliver drugs, take biopsies
By Rachel Ehrenberg
Researchers have created millimeter-sized
metal tools that contort
on command, clamping
shut or popping open
in response to specific
chemical cues. The devices, described
online September 17 in the Journal of
the American Chemical Society, may one
day be used to biopsy a liver, prop open
an artery or deliver drugs to a target site.
It took some doing to make devices
that could respond to chemicals in the
right time and place, yet remain friendly
inside the body. David Gracias of Johns
Hopkins University in Baltimore and
his team began with thin silicon wafers
and coated them with layers of chromium, nickel and gold. Using a high-tech
version of a stencil, the researchers patterned the metal layers into parts that
looked like a flower or the open palm of
The tools are built in an open position (far left) but snap
shut when triggered by certain enzymes (left to right).
a hand. Adding hinges enabled the open
hand to clamp shut.
Then the team added layers of biologically friendly polymers that break down
in the presence of certain enzymes. By
layering these polymers just right the
researchers could selectively degrade
the layers, prompting the device to
spring shut or pop open.
One polymer was derived from collagen, the connective tissue that holds much
of the body together. The other came
from cellulose, the stuff of plant cell walls.
Both collagen and cellulose get
chewed up by specific enzymes. Cel-
lulases, which are made by fungi and
bacteria, destroy cellulose and allow
termites to chew through wood.
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