Rosalind Franklin was a chemist and X-ray crystallographer whose methodical work in the mid-20th century provided fundamental insights into the architecture of life’s most complex molecules. Her career, marked by a dedication to experimental data, profoundly shaped the emerging field of molecular biology. The story of her scientific accomplishments is inextricably linked with the complex history of how major discoveries are attributed and recognized. Her contributions extended far beyond the single molecule she is most often associated with, influencing multiple areas of structural biology.
Early Education and Carbon Research
Franklin’s academic journey began at Cambridge University, where she studied physical chemistry at Newnham College and graduated in 1941. Her subsequent doctoral research was rooted in a practical application of physical chemistry, focusing on the structure of coal and carbon. Working at the British Coal Utilisation Research Association during World War II, she investigated the porosity and density of various carbons, leading to her 1945 PhD thesis on the physical chemistry of solid organic colloids.
Her work defined the distinctions between graphitizing and non-graphitizing carbons, a finding with direct industrial relevance. This research established her early expertise in crystallographic techniques, which she refined during four years in Paris at the Laboratoire Central des Services Chimiques de l’État. Under the mentorship of Jacques Mering, she became an expert in X-ray diffraction, a technique used to determine the atomic and molecular structure of a crystal. This rigorous training honed her capacity for precision and the exacting interpretation of X-ray patterns, which became the foundation for her most significant biological work.
Pioneering X-Ray Diffraction of DNA
Franklin brought her specialized knowledge of X-ray diffraction to the Biophysical Laboratory at King’s College London in 1951, where she was tasked with studying the structure of deoxyribonucleic acid (DNA). She and her PhD student, Raymond Gosling, developed a method to produce finer DNA fibers and precisely control their hydration, which was necessary to capture sharp diffraction images. This meticulous approach allowed her to identify that DNA existed in two forms: a crystalline and drier “A” form and a more hydrated “B” form.
The crucial image was an X-ray photograph of the “B” form, nicknamed “Photo 51,” which she and Gosling captured in May 1952. The image displayed a distinct, symmetrical X-pattern, the definitive signature of a helical structure. She used this pattern to calculate precise parameters of the helix, noting the rise per base pair was 3.4 Å and the pitch of the helix was 34 Å. This ratio strongly indicated that there were ten base pairs per turn.
Furthermore, missing reflection spots suggested that the two chains were not positioned symmetrically, providing evidence for the major and minor grooves present in the structure. Franklin’s interpretation of Photo 51 and her supporting data unequivocally pointed toward a double-stranded helical structure with the phosphate backbone located on the outside. Her commitment was to empirical evidence, believing the pattern itself held the secrets of the DNA molecule.
The Historical Controversy of Recognition
The discovery of DNA’s structure became entangled in a complex dynamic involving scientists at King’s College and those at Cambridge University. Franklin maintained an experimentally driven approach, preferring to verify all data before constructing a theoretical model, a process that created tension with her King’s College colleague, Maurice Wilkins. Without Franklin’s knowledge or permission, Wilkins shared Photo 51 with James Watson during a visit to King’s in early 1953.
Concurrently, Francis Crick gained access to a detailed King’s College progress report containing Franklin’s quantitative measurements derived from her X-ray data, including the precise helical parameters. This unauthorized sharing of her primary data and interpreted results provided Watson and Crick with the necessary empirical evidence to finalize their double helix model. The resulting model was published in the journal Nature in April 1953, alongside a separate paper by Wilkins, and a third paper by Franklin and Gosling presenting her X-ray data as supporting evidence.
The timing and presentation of these articles meant that Franklin’s contribution was viewed as supplementary, rather than foundational, during her lifetime. She died of ovarian cancer in 1958 at the age of 37. When Watson, Crick, and Wilkins were jointly awarded the Nobel Prize in Physiology or Medicine in 1962, Franklin was ineligible because the prize is not awarded posthumously. The full extent to which her meticulous data was used to construct the final model was not widely known until later accounts.
Contributions to RNA and Viral Structures
Following her departure from King’s College in 1953, Franklin moved to Birkbeck College, where she led a research group focused on the molecular structure of viruses. She expertly applied the same X-ray diffraction techniques and rigorous methodology to study the structure of the Tobacco Mosaic Virus (TMV), a rod-shaped virus with an RNA core. Her structural analysis revealed that the TMV was not simply a hollow rod but that its single-stranded RNA was embedded within the protein coat, following a helical path.
Working in collaboration with Aaron Klug, Franklin’s group published several defining papers on viral structures, including the precise location of the RNA molecules within the protein shell. Her work on TMV established foundational concepts in structural virology, including the principle that the protein subunits of a virus form a repeating helical structure to encase the genetic material. Franklin also initiated studies on other viruses, such as the Polio virus, expanding her influence in the field before her premature death.