Rosalind Franklin, whose photographs of the molecular structure of DNA led to a 1962 Nobel Prize for three other scientists, knew that her famous images held the secret of the double helix, new research suggests.
An examination of archival material reveals that Franklin's Photograph 51, which was taken in May 1952 and later published to show the double-helix structure, was specifically taken for the purpose of publication — not, as some narratives have held, an experimental shot that Franklin believed was insignificant. The new research revealed that Photograph 51 was a new exposure of a sample Franklin had already photographed. She started Photograph 51 the same day she saw that photograph, Photograph 49.
"She took it because she wanted to get a really refined version," said study co-author Alistair Sponsel, a historian of science at the Science History Institute in Philadelphia. Making the effort to take a better photograph of the same sample is "a sign she knew she had something really important on her hands," Sponsel told Live Science.
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Francis Crick, James Watson and Maurice Wilkins shared the Nobel Prize in Medicine for the discovery of the double-helix structure of DNA in 1962. As Watson told it in his 1968 autobiography, "The Double Helix: A Personal Account of the Discovery of the Structure of DNA," Franklin's photographs were his "aha" moment: "The black cross of reflections which dominated the picture could only arise from a helical structure," he wrote.
Rosalind Franklin (1920-1958) first took Photograph 49 and then Photograph 51, clues that she was aware of DNA's helical structure.
(Image credit: Donaldson Collection via Getty Images)
Watson further implied that Franklin was a laboratory automaton, good at the X-ray crystallography techniques used to capture the images of the DNA molecule but bad at interpreting her own data. The new archival work, published Monday (Oct. 5) in the Journal of the History of Biology, suggests otherwise.
Franklin's dearth of published notes about Photograph 51 has been used to suggest she missed a major discovery. But Sponsel said her journals show she noted the possible helical shape and rich structural data in her notes for her first picture of the sample, Photograph 49, which she followed up with the more refined image in Photograph 51.
"In Franklin's mind, they were two different types of scientific image," Sponsel said. Photograph 49 was the experimental image revealing exciting new data. Photograph 51 was the showpiece to convey these findings with the most clarity and sharpness possible.
This new understanding of the relationship between the two images, and how Franklin perceived them, is the most important feature of the new work, Sponsel said, which he conducted with molecular biophysicist Brian Sutton of King's College London. The project began when the Science History Institute acquired a new collection of archival material from Rosalind Franklin and her graduate student Raymond Gosling. The two researchers also combed through the archives at King’s College London, where Franklin was working when she took the famous photos.
Sponsel and Sutton think that Franklin's notes and actions reveal why she didn't rush to publish Photograph 51 right away. Her scientific goals, laid out in a report she wrote in February 1952, were to understand the two separate structures of DNA, then known as A and B. Structure B, illustrated in Photographs 49 and 51, turned out to be the double helix that occurs in nature. Structure A is a form DNA takes when it's dehydrated in the lab.
Structure A, when photographed, appeared more data-rich, so Franklin decided to characterize that structure first before studying structure B. But while she did this painstaking work, Wilkins showed Watson her photographs of structure B. The two scientists, together with Crick, then built a detailed model of DNA's double helix and scooped the discovery from under her nose.
Those three men shared the Nobel Prize for the work less than a decade later. Franklin died of ovarian cancer in 1958, making her ineligible for the prize — and leaving her insights to come to light only much later.
Editor's note: This article was updated at 3:23 p.m. ET to fix the caption and subhead, noting that Rosalind Franklin had likely discovered DNA's helical, but not double-helix structure. Also, the top photo is not Photograph 51, but another photo taken by Franklin.
