Rosalind Franklin produced the experimental evidence that proved essential to solving the structure of DNA, and her scientific contributions extended well beyond that single discovery. Before she ever turned her attention to genetics, she had already reshaped the understanding of coal and carbon at a molecular level. After her DNA work, she pioneered the structural study of viruses, generating some of the clearest X-ray images of tobacco mosaic virus ever recorded. That her name is often reduced to “the woman behind Photo 51” undersells a career that shaped the emerging discipline of molecular biology across multiple fronts.
Coal, Carbon, and the Start of a Career
Franklin’s scientific reputation was already established before she began working on DNA. During the late 1940s, working in Paris at the Laboratoire Central des Services Chimiques de l’État, she applied X-ray crystallography to the study of coal and other carbon materials. This was not an academic exercise. Understanding the internal structure of different carbons had direct industrial implications for fuel technology, filtration, and materials science. Franklin demonstrated in 1949 that certain carbon materials had porous structures capable of filtering molecules by size, a property she described as “molecular sieve” behavior.1Interdisciplinary Science Reviews. Rosalind Franklin’s work on coal, carbon, and graphite That concept would go on to become foundational in materials chemistry and industrial separation processes.
Her most influential carbon paper, published in 1951 in the Proceedings of the Royal Society, laid out a classification that scientists still reference. She showed that carbons fall into two distinct classes when heated to extreme temperatures: graphitizing carbons, which gradually develop the layered crystal structure of graphite, and non-graphitizing carbons, which resist that transformation. The difference, she determined, came down to what happens early in the carbonization process. Non-graphitizing carbons develop a rigid system of cross-links between their tiny crystallites, locking them into random orientations within a porous mass. Graphitizing carbons form weaker cross-links, allowing their crystallites to settle into roughly parallel alignment.2Proceedings of the Royal Society of London. Series A. Mathematical and Physical Sciences. Crystallite growth in graphitizing and non-graphitizing carbons This distinction between ordered and disordered carbon structures underpins the modern study of activated carbons, carbon fibers, and other engineered carbon materials.
The Paris years did more than produce good papers. They gave Franklin deep command of X-ray diffraction techniques, the ability to extract three-dimensional structural information from the patterns that X-rays make when they scatter off a crystalline sample. She became unusually skilled at preparing samples, reading diffraction patterns, and performing the mathematical analysis needed to go from a pattern on film to a model of molecular architecture. That combination of experimental precision and analytical rigor is exactly what she brought to King’s College London in 1951, when she turned her attention to a very different kind of molecule.
The DNA Work at King’s College London
Franklin arrived at King’s College in January 1951 to work in John Randall’s biophysics unit, where she was assigned to study the structure of DNA fibers using X-ray diffraction. At the time, the molecular structure of DNA was one of the biggest unsolved problems in biology. Scientists knew DNA carried genetic information, but nobody had worked out how the molecule was arranged in three dimensions.
One of Franklin’s early and critical contributions was recognizing that DNA existed in two distinct forms, which she labeled the A form and the B form. The A form appeared when fibers were relatively dry, and the B form emerged under more humid conditions. Previous researchers had been inadvertently mixing data from both forms, muddling their results. By carefully controlling humidity, Franklin was able to study each form separately, a methodological insight that cleared the path for structural analysis.
The B form turned out to be the more revealing of the two. The X-ray diffraction photograph Franklin took of the B form, known as Photo 51, is one of the most consequential images in the history of science. The pattern displayed a characteristic X-shaped arrangement of spots that indicated a helical structure. Franklin’s experimental work went beyond simply taking the photograph. She measured the dimensions of the molecule, determined the spacing between repeats along the helix, and worked out that the sugar-phosphate backbone of DNA must sit on the outside of the structure, with the bases pointing inward. At a lecture attended by James Watson in late 1951, Franklin presented several potential helical DNA structures, all with the sugar-phosphate backbone toward the exterior.3Cell Press (Chem). The legacy of Rosalind E. Franklin: Landmark contributions to two Nobel Prizes This detail was not a minor point. Watson and Crick’s first attempt at a model had placed the backbone on the inside, and they only got it right after absorbing Franklin’s analysis.
How Franklin’s Data Reached Watson and Crick
The story of how Watson and Crick built their famous double helix model in early 1953 is inseparable from the question of how they gained access to Franklin’s unpublished findings. The short version is that they saw her data without her knowledge or explicit consent, through two channels.
The first was Photo 51 itself. In January 1953, Maurice Wilkins, Franklin’s colleague at King’s College with whom she had a famously strained working relationship, showed Photo 51 to James Watson. Watson later wrote that the moment he saw the photograph, his “mouth fell open and my pulse began to race,” because the helical signature was unmistakable. Franklin had not given permission for the image to be shared.
The second channel was an internal report from the Medical Research Council (MRC), the body that funded the King’s College unit. Max Perutz, who supervised Crick at Cambridge, had received a copy of this report during a visit to King’s in 1952. It contained a page written by Franklin describing her ongoing research, including her finding that the structure of DNA consisted of two chains. Shortly after Watson saw Photo 51, Perutz passed this report to Watson and Crick. The report was not technically confidential, but Franklin had no idea her unpublished findings were circulating outside her laboratory. Armed with her data on the helical geometry, the external backbone, and the two-chain structure, Watson and Crick were able to construct their model within weeks.
Franklin herself has sometimes been depicted as having missed the significance of her own data, as someone who had the answer in her hands but did not see it. The documentary record does not support that characterization. She was working methodically through the mathematics of the A form, which was more complex and less obviously helical than the B form. Her lab notebooks from early 1953 show her converging on a two-chain helical structure independently. She simply did not work at the breakneck, model-building pace that Watson and Crick favored, preferring to let the experimental data lead rather than constructing speculative models first.
Franklin’s Own Published Evidence
When Watson and Crick published their landmark paper in Nature in April 1953, Franklin and her graduate student Raymond Gosling published their own paper in the same issue. Far from being a footnote, Franklin’s paper provided independent experimental evidence supporting the double helix model. She wrote that her results agreed with the Watson and Crick structure “insofar as the basic structure is a helix containing two phosphate-sugar chains per given repeating unit, both chains being co-axial.”4Nature. Evidence for 2-chain helix in crystalline structure of sodium deoxyribonucleate The careful phrasing is characteristic of Franklin: she confirmed what the data supported and reserved judgment on aspects the data had not yet resolved.
This paper is sometimes treated as merely a companion piece validating someone else’s idea. In reality, it represented the culmination of two years of rigorous experimental work that had generated most of the empirical constraints Watson and Crick used. Without Franklin’s measurements of the molecule’s dimensions, her determination of the backbone’s position, and her identification of the two-chain structure in the MRC report, the Cambridge model could not have been built when it was. A 2020 retrospective in Cell described Franklin as having provided “the key data for deriving the double helix structure of DNA” and credited her with pioneering structural studies of colloids, viruses, and RNA that shaped the emerging discipline of molecular biology.5Cell. Rosalind Franklin and the Advent of Molecular Biology
Viruses, RNA, and the Work After DNA
Franklin left King’s College in 1953, moving to J. D. Bernal’s crystallography laboratory at Birkbeck College. This was not a retreat. Bernal’s lab was one of the leading centers for applying X-ray methods to biological molecules, and the move allowed Franklin to pursue the structural study of viruses, a field she would help create. At Birkbeck, she shifted her focus to the three-dimensional structure of tobacco mosaic virus, or TMV, obtaining diffraction patterns of unprecedented detail and clarity.6PubMed. After the double helix: Rosalind Franklin’s research on Tobacco mosaic virus
TMV was an ideal target. It is a rod-shaped virus with a relatively simple architecture, and it was already known to have something to do with a helical arrangement of protein subunits around a core of RNA. But nobody had worked out the precise geometry. Franklin’s X-ray images showed that the diffraction pattern was more complex than a simple continuous helix would produce. Working with Aaron Klug, a young crystallographer who had recently joined Birkbeck, she figured out why. The pattern’s complexity arose because there was a non-integral number of coat protein subunits per turn of the helix. Through detailed measurement of the spacing between layer lines in the diffraction pattern, Franklin and Klug established that there were almost exactly 49 coat protein subunits in every three turns of the TMV helix, firmly demonstrating its helical symmetry.7Biographical Memoirs of Fellows of the Royal Society. Sir Aaron Klug OM. 11 August 1926—20 November 2018
Franklin also determined the location of TMV’s RNA within the virus particle and studied other viruses, including the spherical turnip yellow mosaic virus. Her group’s work on TMV established the basic principles of how simple viruses are assembled from protein and nucleic acid components, principles that would become central to virology and to the broader field of structural biology. The collaboration with Klug was particularly productive. Their first joint publication was Klug’s first paper on any biological topic, and it launched a partnership that continued until Franklin’s death.
The Relationship Between Franklin’s Work and Two Nobel Prizes
Franklin died of ovarian cancer on April 16, 1958, at the age of 37. The cause of her cancer is not known with certainty, but years of close work with X-ray equipment, sometimes with inadequate shielding, may have been a contributing factor. She continued working almost until the end, publishing papers on virus structure from her hospital bed.
Four years after her death, Watson, Crick, and Wilkins received the 1962 Nobel Prize in Physiology or Medicine for determining the structure of DNA. Franklin’s contribution was barely mentioned in the ceremony. Watson’s 1968 memoir, The Double Helix, further complicated her legacy by portraying her in terms that many scientists and historians found dismissive and sexist, focusing on her appearance and temperament rather than her scientific ability.
The question of whether Franklin would have shared the Nobel Prize had she lived is impossible to answer definitively. The Nobel can be awarded to at most three people, and there were already three laureates. Some historians have argued that Franklin’s experimental contribution was at least as significant as Wilkins’s, and that she had a stronger claim to a share of the prize. Others point out that the Nobel committee might have split the award differently, perhaps giving the Chemistry prize to Franklin for her crystallographic work and the Medicine prize to Watson and Crick for the biological model. The Nobel is not awarded posthumously, so the question remained hypothetical.
What is less hypothetical is the connection between Franklin’s virus research and a second Nobel Prize. Aaron Klug received the 1982 Nobel Prize in Chemistry for developing crystallographic electron microscopy and elucidating the structure of biologically important nucleic acid-protein complexes. Much of Klug’s foundational work on virus structure grew directly out of his collaboration with Franklin at Birkbeck. After her death, Klug took over leadership of her research group and continued the structural virology program she had built. He consistently credited Franklin’s influence on his career and scientific direction. The retrospective view of Franklin’s legacy thus touches not one but two Nobel Prizes, one she was excluded from and one that grew from seeds she planted.3Cell Press (Chem). The legacy of Rosalind E. Franklin: Landmark contributions to two Nobel Prizes
Why the “Wronged Heroine” Framing Is Incomplete
Popular accounts of Franklin often cast her primarily as a victim of sexism, someone whose work was stolen by men who got all the credit. There is real substance behind that framing. The unauthorized sharing of her data was a genuine breach of scientific ethics, and the culture at King’s College was unwelcoming to women in ways that have been well documented. Watson’s patronizing portrayal of her in The Double Helix compounded the injustice.
But reducing Franklin to the role of wronged heroine does its own kind of disservice, because it centers her story on what was done to her rather than what she did. Her coal and carbon research alone would have secured her a respected place in materials science. Her virus work was world-leading and opened an entirely new area of structural biology. She published over 40 papers in a career cut short at 37, spanning physical chemistry, carbon science, DNA, and virology. She led her own research group, secured her own funding, and trained students who went on to distinguished careers.
The more interesting question about Franklin is not whether she was treated fairly, though she was not, but how a single scientist managed to make foundational contributions across so many different fields in such a short time. The connecting thread was her mastery of X-ray diffraction and her insistence on letting experimental data dictate conclusions rather than building speculative models first. That methodological philosophy produced slower, less dramatic discoveries than the model-building approach Watson and Crick preferred, but it also produced work of exceptional reliability. Her coal classifications are still used. Her DNA measurements were the empirical foundation of the double helix. Her virus structures launched a field. The breadth of that record speaks for itself, and it does not need a narrative of victimhood to be remarkable.
Franklin’s Influence on How Science Studies Molecular Structure
Beyond any single discovery, Franklin helped establish the practice of using X-ray diffraction to study biological molecules at atomic resolution. When she began her career, crystallography was primarily a tool of physics and chemistry, used to study minerals, metals, and simple inorganic compounds. Applying it to large, flexible biological molecules like DNA and viral proteins required developing new techniques for sample preparation, new approaches to interpreting diffraction patterns, and new mathematical methods for extracting structural information from imperfect data.
Franklin was not the only scientist pushing crystallography into biology during the 1950s, but she was among the most skilled and productive. Her ability to obtain high-quality diffraction images from biological fibers and crystals was recognized by her contemporaries as exceptional. The techniques she developed for controlling the hydration of DNA fibers, for instance, were essential to distinguishing between the A and B forms and would not have been obvious to someone approaching the problem from a purely theoretical perspective.
Structural biology as a discipline, the systematic effort to determine the three-dimensional shapes of biological molecules, grew enormously in the decades after Franklin’s death. Today it encompasses not just X-ray crystallography but also cryo-electron microscopy and nuclear magnetic resonance spectroscopy. Thousands of protein and nucleic acid structures are deposited in public databases every year. The intellectual roots of that enterprise run through a relatively small number of mid-twentieth-century laboratories, and Franklin’s work at King’s College and Birkbeck was part of the foundation. Her contribution was not just the specific structures she solved but the demonstration that careful experimental crystallography could reveal how biological molecules are built and, by extension, how they function.