DNA Photos May Be Errors, Scientists Say

In their unending quest to understand DNA, the basic molecule of life, scientists were elated a couple of years ago when researchers came up with the first photographs of the helical structure that bears the genetic blueprints for all living creatures. But it turns out that some of those photos may have been false images.

Some of the scientists involved in the earliest efforts are reporting today that some images may have been of a graphite material used to hold the DNA rather than of the molecule itself.

However, other scientists who produced similar photos last summer say they are convinced that their images are of the real thing because they show features that would not be present in graphite.

The disclosures reveal the difficulty of capturing direct images of molecular structures, prompting the pioneering researchers to warn their colleagues to use something other than graphite to hold DNA when they study it with their scanning tunneling microscopes.

The first images were produced by a team from Lawrence Berkeley Laboratory and Lawrence Livermore National Laboratory. But two of the scientists engaged in that effort said in a report published in today’s issue of the journal Science that when they subsequently looked at some forms of graphite alone--without the DNA--they saw some of the same features they had thought could have come only from DNA.

Chemist Thomas Beebe Jr., who has since moved to the University of Utah, and his colleague, Carol Clemmer, said in the report that the graphite “could have been confused in the past with DNA,” and they advised others to switch to something other than graphite to hold the DNA.

John Baldeschieler of Caltech thanked the researchers for their advice, but added that he is “quite confident” the image produced by his team last summer is valid. That photo was so sharp that individual atoms could be seen.

“They make a useful point,” he said, “but we’ve known about this for years.”

He said members of his team have “many confirming observations” that they photographed DNA, not graphite.