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发帖数: 12367 | 1 Italian physics professor Enzo Di Fabrizio captures twisted ladder that
props up life
DNA's double-helix structure is on display for the first time in this
electron microscope photograph of a small bundle of DNA strands.
Fifty-nine years after James Watson and Francis Crick deduced the double-
helix structure of DNA, a scientist has captured the first direct photograph
of the twisted ladder that props up life.
Enzo Di Fabrizio, a physics professor at Magna Graecia University in
Catanzaro, Italy, snapped the picture using an electron microscope.
Previously, scientists had only seen DNA's structure indirectly. The double-
corkscrew form was first discovered using a technique called X-ray
crystallography, in which a material's shape is reconstructed based on how X
-rays bounce after they collide with it.
A bundle of DNA is supported by two silicon pillars.
But Di Fabrizio and his colleagues developed a plan to bring DNA out of
hiding. They built a nanoscopic landscape of extremely water-repellant
silicon pillars. When they added a solution that contained strands of DNA
into this scene, the water quickly evaporated and left behind cords of bare
DNA that stretched like tightropes between the tiny mesas.
They then shone beams of electrons through holes in the silicon bed, and
captured high-resolution images of the illuminated molecules.
Di Fabrizio's images actually show a thread of several interwoven DNA
molecules, as opposed to just two coupled strands. This is because the
energy of the electrons used would be enough to destroy an isolated double
helix, or a single strand from a double helix.
But with the use of more sensitive equipment and lower energy electrons, Di
Fabrizio thinks that snapshots of individual double helices will soon be
possible, New Scientist reports.
Molecules of DNA, or deoxyribonucleic acid, store the genetic instructions
that govern all living organisms' growth and function.
Di Fabrizio's innovation will allow scientists to vividly observe
interactions between DNA and some of life's other essential ingredients,
such as RNA (r ibonucleic acid ). The results of Di Fabrizio's work were
published in the journal NanoLetters. | b***u
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