Beware the 'Allure of the Image'

Stephen Curry at The Guardian's Occam's Corner blog takes issue with some media coverage of a recent paper describing the structure of DNA using electron microscopy.

Curry, a professor of structural biology at Imperial College, says that several internet reports contained "inaccurate information" about the study, most notably that the paper described the helical structure of a single DNA strand, when in fact the researchers studied a bundle of DNA molecules.

The novel aspect of the paper, he says, is that it used a high-contrast method that produced an image about "a thousand times finer" than the seminal X-ray crystallography images of DNA created by Maurice Wilkins and Rosalind Franklin nearly 60 years ago.

"There is certainly some fine structure in the image. There are repetitive features of the size expected for the helical structure in DNA," Curry says. Nevertheless, it "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."

Furthermore, claims that the study will lead to new insights regarding how proteins and other molecules interact with DNA are also bogus, he says, largely due to the fact that the DNA is bundled. Even if it were possible to isolate a single DNA strand, "the fact that the method relies on largely drying out the sample makes it unsuitable for analyzing any proteins bound, since these molecules depend critically on being immersed in water to work properly."

He speculates that the "allure of the image" might have "dulled" the vision of reporters who covered the story.

"What frustrated me is that, in spite of having an image served up to them, they didn't look at it properly, and that allowed errors to creep in," he says.