The structure of DNA proposed by William Astbury and Florence Bell in 1938
The first 3D structure of DNA was published in 1938. It was generated by Florence Bell, a scientist you need to know.
One thing that we lose in the coverage of major scientific discoveries is all of the work that those advances were built on.
A perfect example of this is Watson and Crick's solving of the structure of DNA in 1953.
This wasn't just a synthesis of data they obtained from Maurice Wilkins via Rosalind Franklin (and others), but it also wouldn't have been possible without the early work of William Astbury and Florence Bell.
This is that story.
In the 1930's, William Astbury spent his days analyzing biological fibers using a technique called x-ray diffraction.
He was particularly interested in coiled fibers like those found in wool (keratin) and other textiles and was the first to characterize the structural changes in proteins as they are stretched.
He referred to these as the α-form and β-form, and laid the groundwork for Linus Pauling's discovery of the α-helix and β-strand in 1951!
Astbury quickly got a reputation for his expertise in x-ray diffraction, and was sent purified biological material to characterize from all over Europe.
In 1937, apparently elbows deep in things to characterize, he sent a letter to another renown crystallographer, Lawrence Bragg, asking if he knew of any rockstar crystallographers that were available to help with his studies.
Bragg recommended Florence Bell, a Cambridge grad who learned how to do crystallography from yet another x-ray luminary, JD Bernall.
A short correspondence later and Bell left her job working for Bragg to start her graduate work under the tutelage of Astbury.
While her research was focused on lots of different biological fibers, Bell's most important work was with DNA.
She showed that the key to obtaining the most informative images was the use of high molecular weight DNA.
The best source for this was calf thymus, and the diffractions she obtained from these fibers indicated that DNA had an ordered structure.
This finding was published in 1938 and was also presented at Cold Spring Harbor later that year by Astbury.
They described their structure of DNA as a 'pile of pennies' and a depiction of it can be seen in the figure above.
Their calculations also showed that the DNA nucleotides were 3.3 Å apart and they were stacked one on top of another.
While this might not seem like a historic achievement, it set the foundation for everything that would follow.
With a few tweaks and the discovery that DNA can exist in two forms depending on the humidity during drying, Rosalind Franklin and Raymond Gosling built on Bell's early work to generate photo 51 - the key diffraction of DNA used to solve the structure of DNA in 1953.
Brian Krueger