Now you see it, now you don’t


It’s not often that the world gets excited about transmission  electron microscopy (TEM), so when it does, there must be a good reason. Last week, this  image from the Italian Institute of Technology in Genoa began making waves on  the internet, with people claiming that  it showed the double helix of a single strand of DNA.

What an achievement that would be! DNA is the fundamental building block of our biology, and is essential for all known forms of life, yet  its tiny size means that it has always eluded direct imaging. Even today, 60  years since Watson and Crick discovered its famous double helix, we still use  the same X-ray diffraction (XRD) experiments to probe the nature of DNA. These  experiments can show us how the atoms in the molecule are arranged, but they can’t  directly image it.

So a picture of the famous double helix itself would be a  major accomplishment – except this isn’t one.

To be precise, it is a picture of DNA, but it’s not a single strand. The Italian team found that transmission electron microscopy is too high-energy to work with a single strand of DNA, and so used a ‘cord’ of six strands woven around a seventh for their work. So the thick wavy line is actually a result of lots of strands lining up next to one another, as in these simulations.

The TEM required seven strands of DNA, and produced an image of all of them, as represented on the right.

Does it matter? I’d argue, probably not. After all, most people won’t care whether they saw one strand or seven; they just want to be impressed with the wonders of modern day science. What’s more, it doesn’t alter the fact that this was a tremendous undertaking – in order to produce the image, the researchers had to etch tiny (12 micrometer tall) pillars from a flat surface, they then hung the DNA cords from these, like a clothes line. Considering I find it hard to thread a needle, I’d say this is nothing to be sniffed at.

Of course it’s tempting to say that these people have a duty to get their facts right, and that they’re spreading misinformation, and that’s true – for that reason (and to its credit), the website later corrected the error. But the mistake doesn’t change the essence of the discovery, which is that DNA was directly imaged for the first time. And the web page links to the journal article, so anyone who has more than a passing interest has a chance to find out the truth for themselves; for those that do not, it’s probably not that important.

Besides, scientific journals and websites serve very different purposes: no one visits io9 for professional scientific information, and no one flicks through a journal for snappy science news. By avoiding the original journal style, the website can reach more people, and communicate more science. If the alternative means alienating readers in the pursuit of perfection, I know which method I would prefer.

REFERENCE: F. Gentile et al. NANO Letters, 2012, article ASAP,

IMAGES: Reproduced from the cited paper with permission.

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