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What DNA actually looks like


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This blog often covers small things: insects, spiders, slime molds and so on. In the scheme of biology, though, the usual fare here is pretty big.

In contrast, here is something truly small- the first high-contrast microscope image of an isolated molecule bundle of DNA:

Figure 2 from Gentile et al 2012.

Researchers at the Istituto Italiano di Tecnologia strung a molecule between two nano-towers and subjected it to transmission electron microscopy at extreme magnification. Until last week the double helix model had been an indirect inference, albeit an extremely robust one, from techniques like crystallography. The new paper, in Nano Letters, is just the thing for those who like to see evidence with their own eyes.

update: Stephen Curry provides a clarification and correction:

What is actually new in the paper is that the authors have been able to take a high-contrast image of a DNA fibre (made up of a bundle of DNA double-helices) using electron microscopy. They did this by drying out a drop of DNA dissolved in water over a layer of silicon that had been micro-fabricated to have an array of tiny pillars across its surface. As the water evaporated, strands of DNA were left stretched between the pillars. Because they are suspended above the silicon base, it was possible to get a good image of the DNA fibres (you get poorer contrast if the DNA is lying on a solid surface)…

And what do they see? There is certainly some fine structure in the image. There are repetitive features of the size expected for the helical structure in DNA. But it was clear to the Italian researchers and should have been clear to anyone looking at the picture in their online abstract, that the image is not of a single molecule of DNA but a bundle of them.

 


source: Gentile, F. et al. 2012. Direct Imaging of DNA Fibers: The Visage of Double Helix. Nano Lett. DOI:10.1021/nl3039162

Alex Wild About the Author: Alex Wild is an Illinois-based entomologist who studies the evolutionary history of ants. In 2003 he founded a photography business as an aesthetic complement to his scientific work, and his natural history photographs appear in numerous museums, books, and media outlets. Follow on Twitter @myrmecos.

The views expressed are those of the author and are not necessarily those of Scientific American.

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  1. 1. Hootysdad 4:33 pm 11/30/2012

    Wouldn’t it be something………someday…….to view a video here of the DNA molecule dividing?? I would like to still be around and living if that ever happens.

    Link to this
  2. 2. Chryses 5:03 pm 11/30/2012

    Very cool indeed!

    Hootysdad, I too hope to see that video!

    Link to this
  3. 3. sauIt 8:00 am 12/1/2012

    So DNA resembles a machine bolt rather than a wood screw.

    Link to this
  4. 4. Rotarix 9:00 am 12/1/2012

    So just to point out that this is what a bundle of DNA molecules looks like…it is not a fuzzy picture of the double helix but a fuzzy picture of a bunch of double helices together. Very impressive and beautiful none the less.

    Link to this
  5. 5. stargene 3:45 am 12/2/2012

    Truly beautiful and a marvel. And a beautiful testament
    to the genius and ingenuity of scientists, like Crick,
    Watson, Franklin, Wilkins and others. And I include
    here all their peers whose work did not arrive at the
    double helix, but explored other possibilities.

    Link to this

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