November 29, 2012 - It's the most famous corkscrew in history. Now an electron microscope has captured the famous Watson-Crick double helix in all its glory, by imaging threads of DNA
resting on a silicon bed of nails. The technique will let researchers see how proteins, RNA
and other biomolecules interact with DNA.
The structure of DNA
was originally discovered using X-ray
crystallography. This involves X-rays scattering off atoms in crystallised arrays of DNA
to form a complex pattern of dots on photographic film. Interpreting the images requires complex mathematics to figure out what crystal structure could give rise to the observed patterns.
The new images are much more obvious, as they are a direct picture of the DNA
strands, albeit seen with electrons rather than X-ray
photons. The trick used by Enzo di Fabrizio at the University of Genoa, Italy, and his team
was to snag DNA
threads out of a dilute solution and lay them on a bed of nanoscopic silicon pillars.
The team developed a pattern of pillars that is extremely water-repellent, causing the moisture to evaporate quickly and leave behind strands of DNA
stretched out and ready to view. The team also drilled tiny holes in the base of the nanopillar bed, through which they shone beams of electrons to make their high-resolution images. The results reveal the corkscrew thread of the DNA
double helix, clearly visible. With this technique, researchers should be able to see how single molecules of DNA
interact with other biomolecules.