Rosalind Franklin’s X-ray work played a crucial role in the discovery of DNA’s structure.
Moreover, Franklin discovered the previously unsuspected B type DNA, establishing that DNA molecules can exist in more than one form.
We now know that B type DNA is DNA’s usual structure within living cells.
Rosalind Elsie Franklin was born on July 25, 1920 into a socially well-connected, upper-class family in the United Kingdom’s capital city, London. Her father was Ellis Arthur Franklin, an investment banker; and her mother was Muriel Frances Waley, daughter of a lawyer. Rosalind was the second of their five children.
In addition to his banking work, Rosalind’s father helped less privileged people by teaching electricity and magnetism at London’s Working Men’s College. Her mother did charitable work helping the elderly, the unemployed, and unmarried mothers.
Rosalind was educated at private schools, where her outstanding intellect was soon identified.
Her parents encouraged all of their children to have their own opinions and to discuss and debate the issues of the time. Rosalind could debate with unusual vehemence, and would continue to do so in adulthood.
She began high school – St Paul’s Girls’ School – in 1931, at age 11 – and worked hard.
Her scientific talents were exceptional.
Once, when asked to choose a book to be bought as a school prize, Rosalind opted for Arthur Eddington’s 1935 New Pathways in Science. Its themes included quantum theory, subatomic energy, and group theory – rather advanced reading for a 15-year-old. She already sensed that her destiny lay in physical science.
Rosalind was also strong in Latin, German, and French, and skilled at sports.
She formed some enduring friendships at school, but was otherwise shy and she could be difficult with others, including her teachers.
Rosalind left school in 1938, by which time there was a growing acceptance in the UK that a war with Nazi Germany was likely. Rosalind’s Jewish parents had taken two children fleeing from the Nazi regime into their home. When Rosalind won a university scholarship, she donated it to a refugee student.
Before beginning university, she abandoned any spiritual adherence to Judaism, but not her cultural affinity.
Arriving at the University of Cambridge in 1938, age 18, Franklin opted to study Natural Sciences. She worked hard, and participated fully in the university’s societies, joining the Chemistry Club, the Mathematics Club, and the Jewish Society.
Blunt as ever, she made a complaint about the standard of chemistry lectures. Her complaint was effective and the lectures improved.
By the time her second year at Cambridge was due to start, the war in Europe had begun. Her father at first refused to pay for her second year, pleading with her to postpone her education and get involved with the war effort. His wife persuaded him to relent.
After three years at Cambridge, Franklin sat her final exams. She graduated with second class honors, a result which disappointed her.
The outcome was no surprise to Fred Dainton, her supervisor. Although her natural ability was very high, Franklin was a perfectionist. She spent too much time composing perfect answers to the first questions in exams, leaving too little time to complete the whole exam to the same standard.
Nevertheless, Franklin was told privately that she had come top in physical chemistry, and she was awarded a research fellowship.
She began researching the speed of polymerization reactions. Her doctoral advisor was the future Nobel Prize winning chemist Ronald Norrish. Franklin quit after a year: she did not get along with her colleagues, she did not like the work she was doing, and, in her own words, ‘despised’ Norrish, who at this stage in his career was drinking heavily.
Coals and Carbon
In 1942, in the middle of World War 2, Franklin began working in coal utilization research in London. Coal – an impure form of carbon – was absolutely vital for fueling the British war effort.
Like a sponge, coal is porous, with networks of tiny tunnels running through it. The properties of these tunnels are important to coal’s efficiency as a fuel.
Franklin showed how to classify coals by their porosity and established how porosity affects fuel performance.
A Ph.D. and Carbon as a Molecular Sieve
Franklin found that many tunnels in coal are about the same diameter as gas molecules. She discovered that coal can act as a molecular sieve – its fine structure can be used to separate mixtures of molecules.
Today, carbon-based molecular sieves are used, for example, to extract oxygen from air.
Franklin’s coal work gave her the data she needed for a Ph.D. thesis. Cambridge awarded her a doctorate in 1945.
Paris and X-ray Diffraction
In 1947, age 27, Franklin moved to Paris. She lived unusually cheaply in the French capital, because her landlady’s priority was to find a respectable tenant.
Franklin joined Jacques Mering’s team of researchers at the French government’s central laboratory, where Mering was pioneering X-ray diffraction studies of amorphous solids – i.e. solids like coal with no regular crystalline structure.35 years earlier, in 1912, Lawrence Bragg had discovered how X-ray diffraction can be used to find the locations of atoms in crystalline solids and so build pictures of molecules. Franklin was now going to become an expert in its use.
Soon she was using X-ray diffraction to study the atomic structure of coal.
She was particularly interested in the process of transforming amorphous coal into crystalline graphite, an essential material in the new field of nuclear research. Franklin successfully identified the types of amorphous carbon that can be transformed into crystalline graphite.
In 1949, Franklin began thinking about returning to her home city. Her feelings about this were ambiguous; she enjoyed the company of French people more than English people.
London, X-ray Diffraction, and DNA
In January 1951, age 30, Franklin began a postdoctoral fellowship in biophysics at King’s College, University of London. The laboratory was unusual for the era: 8 of its 31 researchers were female, some in senior positions.
Franklin had been recruited to work on the 3D structure of proteins. In fact, when Franklin arrived at King’s, she began working on the 3D structure of DNA.
The change of plan was Maurice Wilkins‘ idea. Wilkins, a senior scientist at King’s College, suggested to the head of the laboratory, John Randall, that Franklin should join his DNA team.
Franklin was soon unhappy at King’s. She had grown used to her colleagues in Paris discussing intellectual concepts, political theory, and philosophy in their spare time. In comparison, King’s seemed dull, with spare-time conversations either focusing on work or mundane topics such as sport.
DNA at King’s College before Franklin
Maurice Wilkins was interested in DNA. He had obtained a perfect sample of it, and had drawn the DNA into microfibers. His doctoral student, Raymond Gosling, found that under suitable conditions the DNA microfibers were crystalline. This was a major breakthrough. Crystals presented a perfect target for X-ray diffraction, which could be used to study 3D structure.
One of the physicists at King’s, Alexander Stokes, looked at the diffraction patterns in Gosling’s photos and concluded that DNA molecules were probably helix-shaped. He had already seen helical virus crystals give similar patterns.
In fact, helices were increasingly the talk of the scientific world. In November 1950, two months before Franklin started at King’s, Linus Pauling had published a short letter announcing his discovery of helical protein molecules.
A Misunderstanding Poisons a Relationship
Sadly, Maurice Wilkins and Rosalind Franklin, working in the same field, in the same laboratory, would eventually stop talking to one another. They worked separately on the structure of DNA.
The tension first arose because, unknown to Wilkins, his boss Randall had told Franklin she would take over Wilkins’ work on DNA. Remarkably, he didn’t tell Wilkins this. The situation was worsened by the fact Wilkins was absent for the first week or two following Franklin’s arrival, when Franklin took over from Wilkins as Gosling’s doctoral advisor.
When Wilkins returned, Franklin thought he was trying to muscle in on her research territory. This was awkward because, although not her manager, he was a senior scientist.
On the other hand, Wilkins believed Franklin had joined his DNA team and he was bewildered by her unwillingness to communicate.
Franklin and Wilkins each thought the other was acting unreasonably. Wilkins, a painfully shy man, was baffled by Franklin’s growing hostility. Franklin could be highly confrontational and actually enjoyed heated arguments. Wilkins would recoil from such confrontations, so the air was never cleared between them.
The sour atmosphere left Raymond Gosling, the research student, in an uncomfortable position.
Gosling came to believe that Randall deliberately engineered the conflict, thinking the competition between Franklin and Wilkins would be beneficial to the laboratory’s work program!
In fact, Wilkins and Franklin were both miserable. Away from the laboratory Franklin cried tears over how awful the situation was. Wilkins would agonize about repairing their relationship, but the formidable persona Franklin presented to him, compounded by his own hesitant personality, always thwarted his good intentions.
Major Progress: Two Types of DNA
Franklin, with the benefit of her experience in Paris, started setting up X-ray equipment to take the best X-ray diffraction photos ever seen at King’s.
Eight months into her new job, in September 1951, she made a pivotal breakthrough, discovering a previously unsuspected second type of DNA.
She found that when DNA is exposed to high levels of moisture its structure changes. Franklin called the high moisture form she and Gosling discovered ‘B DNA.’ The drier form became ‘A DNA.’
We now know that B DNA is DNA’s usual arrangement within living cells, where the environment is very moist.
As a consequence of her discovery, Franklin realized that earlier X-ray studies of DNA were less helpful than they might have been – the DNA had contained a mixture of A and B types, causing blurring in the X-ray diffraction photos.
A Meeting with Crick and Watson
A month after Franklin’s discovery of B DNA, she gave a presentation about it at a colloquium.
One very interested listener was a young American researcher working at the University of Cambridge. His name was James Watson, and he had become rather fanatical in his pursuit of DNA’s structure.
Watson remembered enough of the information Franklin presented at the colloquium to allow himself and another Cambridge DNA enthusiast, Francis Crick, to build a 3D scale model of DNA. They had been inspired to do this by Linus Pauling’s discovery of the protein alpha-helix using a 3D scale model.
However, Watson had not taken notes at Franklin’s presentation; he remembered some of the details wrongly and so naturally enough the model was also wrong.
Watson and Crick invited the DNA researchers from King’s to see the model.
And so the main players in the story came together, including:
- Franklin, Wilkins, and Gosling from King’s College, London
- Watson and Crick from Cambridge’s Cavendish Laboratory
Watson and Crick’s model was a triple helix. Franklin, ever cautious about drawing premature conclusions, argued that her X-ray diffraction photos provided no certainty of a helix.
Torpedoing Crick and Watson
Moreover, Franklin launched a polite but nonetheless devastating attack on physicist Crick and biologist Watson’s first attempt at a model of DNA. Watson’s faulty memory, combined with the duo’s inexperience in chemistry, had resulted in basic errors.
Undeterred, Crick and Watson hoped to develop their model further and asked the King’s people if they would like to collaborate on DNA’s structure, but Franklin and Gosling did not wish to.
When he got reports of the meeting, Lawrence Bragg, head of Cambridge’s Cavendish Laboratory, instructed Crick and Watson to stop their DNA work – they were not to compete with King’s.
On May 2, 1952, Raymond Gosling took Photo 51 – an X-ray diffraction photo of B DNA that would become both famous and notorious. About a month later, Franklin told Randall she would be leaving King’s to do X-ray work at Birkbeck College, also in London.Photo 51 was so perfect that it screamed ‘helix’ to anyone familiar with X-ray diffraction. However, photos of A DNA were less clear-cut and the perfectionist in Franklin wanted to understand why.
There was much information to be gleaned from Photo 51.
- the distance between one full twist of the helix and the next
- the diameter of the helix
- Much more subtly, photo 51 revealed how some of DNA’s chemical groups were arranged:
- heavy phosphate groups lay on the outside of the helix
- The bases that carry the genetic code lay inside the helix.
In January 1953, with Franklin’s departure looming, Maurice Wilkins became Gosling’s doctoral advisor. Gosling showed Photo 51 to Wilkins, who was astonished by two things: the photo’s sharpness, and that it had existed for eight months and nobody other than Franklin and Gosling had seen it before.
Wilkins showed Photo 51 to James Watson. In truth, other than marvel at the sharpness of the image and note how clearly the image confirmed DNA’s helical structure, Watson could do little else with it.
Photo 51 did, however, intensify his urgent determination to get back to model building, because the helical structure was so obvious.
The Return of Crick and Watson
Also in January 1953, Lawrence Bragg became aware that Linus Pauling was working on DNA’s structure. Bragg had a long standing grudge against Pauling, and the prospect of Pauling winning the DNA race was intolerable to him.
So, Bragg now authorized Crick and Watson to restart their DNA model work, hoping they would beat Pauling.
In mid-February 1953, Crick saw a report written two months earlier by Franklin for the Medical Research Council (MRC). The report was not confidential and Crick was also working in an MRC funded laboratory.
Crucially, Franklin’s report said that DNA’s crystal space group was face-centered monoclinic. Instantly Crick knew this meant there were two matched helices running in opposite directions in DNA – a dyad.
Meanwhile, Watson discovered how DNA’s bases – the chemical groups that carry the genetic code – would slot perfectly within a double helix.
By March 7, 1953, Crick and Watson had cracked the DNA code.
The Missed Opportunity
Although Franklin provided data essential to the discovery of DNA’s structure, she missed out on discovering it herself. With the benefit of hindsight, we know there were two vital pieces of the jigsaw she did not fit.
- Firstly, with Dorothy Hodgkin’s help, Franklin had found that DNA’s space group was face-centered monoclinic. She did not appreciate the full implications of this for DNA’s structure, although her laboratory notebooks show she was knocking on the door.
- Secondly, Franklin could not see how the bases would fit into DNA’s structure. Again, her laboratory notebooks show that she was getting close.
Franklin would later ruefully tell her friend and colleague Aaron Klug that she had missed the significance of the horizontal dyad.
She had been hindered by several factors:
- Her perfectionist streak, noted by her supervisor when she was an undergraduate. Franklin was unwilling to experiment with scale models of DNA before completing a full mathematical analysis of her data. By the time she considered using a model, it was too late. Linus Pauling, however, had already shown that model building can be an integral part of the discovery process.
- She was trying to come to terms with A DNA, whose X-ray photos were much less clear-cut in pointing to a helix than photos of B DNA. Sympathizing with her situation, Francis Crick would later write that he was glad he hadn’t seen X-ray images of A DNA, because they would have worried him.
- She wasn’t part of a team like the Crick-Watson partnership. Crick and Watson talked for hours and argued endlessly, without animosity, about DNA. However, arguments within the poisonous atmosphere at King’s were generally destructive. In fact, there weren’t many arguments – non-communication was the norm, apart from conversations between Franklin and her student Gosling.
- Solving DNA’s structure required creativity. It’s hard to be scientifically creative when you’re feeling utterly miserable.
Franklin and Gosling’s data proved essential to Crick and Watson’s discovery. Many commentators believe Franklin and possibly Gosling should have been co-authors of the famous Watson-Crick paper.
Instead, Randall and Bragg, the heads of the laboratories in London and Cambridge, agreed that the researchers would write separate papers.
On April 25, 1953, three papers appeared in Nature: one from Watson and Crick; one from Wilkins, Stokes & Wilson; and one from Franklin & Gosling. In truth, even though the laboratory heads had agreed to publish separate papers, Watson and Crick could still have offered a much more fulsome acknowledgement of the part Franklin’s data had played in their discovery:
We have also been stimulated by a knowledge of the general nature of the unpublished experimental results and ideas of Dr. M. H. F. Wilkins and Dr. R. E. Franklin and their co-workers at King’s College, London.
helped us to obtain the structure was mainly obtained by Rosalind Franklin, who died a few years ago.”
Franklin never realized just how much Watson and Crick’s discovery owed to her data.
Crick and Franklin became friends; she would go on vacation with the Crick family, and visit and stay at their home.
Crick, Watson and Wilkins shared the 1962 Nobel Prize in Medicine for the discovery of DNA’s structure and the way it replicates. Rosalind Franklin died in 1958, and Nobel Prizes are not awarded posthumously.
Tobacco Mosaic Virus
In March 1953, Franklin moved to Birkbeck College to head her own research group. There she used X-ray diffraction to study the 3D structure of the tobacco mosaic virus and other plant viruses.
She recruited Aaron Klug to her team, and with their doctoral students made significant contributions in this field, discovering that the tobacco mosaic virus consists of a single molecule of RNA embedded in a helical array of protein molecules.
Some Personal Details and the End
Franklin did not marry or have children. Her friends suspected she fell in love with Jacques Mering, the director of the Paris laboratory she worked in.
It was Franklin’s destiny to die young. In a cruel twist of fate, her own DNA may have carried the destructive agent – Ashkenazi Jews have a hereditary predisposition to ovarian cancer.
Also, her work with X-rays was not risk-free. In Paris Marie Curie had died from the effects of radiation. Her Nobel Prize winning daughter Irène Joliot-Curie suffered the same fate, as did many other early French researchers.
Since the Curie era, safety standards had been improving. At one point, Franklin had been barred from the Paris laboratory for several weeks because her radiation monitoring badge showed she had suffered excessive X-ray exposure. Workers at King’s College noted she did not wear the lead apron she was meant to when the X-ray machine was in use there. None of them felt confident enough to challenge her over this, and she wasn’t the only worker to flout the safety rules.
Franklin was incredibly brave through the final stages of her cancer. Unable to walk, she literally crawled up stairways between laboratories at Birkbeck, determined that the cancer would not stop her work. Her dedication left many of her co-workers in tears.
Rosalind Franklin died of ovarian cancer in London on April 16, 1958. She was just 37 years old. She was buried in the Franklin family plot in the United Jewish Cemetery in Willesden, London.
Her family only realized her true eminence as a scientist when they read her glowing obituary in the Times.
As a teenager she had donated her university scholarship to a refugee. At the end of her life, she continued helping others. She bequeathed her co-worker Aaron Klug £3,000. This was a considerable sum: the average price of a house in the UK was about £2,000. She felt the money would free Klug from financial worries: Klug went on to win the 1982 Nobel Prize in Chemistry. Two of her friends with young children to support received £1,000 each.
In life Rosalind Franklin had left enduring legacies in every part of science she touched. In death her legacies were more personal, but still far-reaching.
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Image of Raymond Gosling by Raymond Gosling under the Creative Commons Attribution-Share Alike 3.0 Unported license