William Astbury

William Thomas Astbury FRS (25 February,1898 — 4 June,1961) was an English physicist and molecular biologist who made pioneering X-ray diffraction studies of biological molecules. His work on keratin provided the foundation for Linus Pauling's discovery of the alpha helix. He also studied the structure for DNA in 1937 and made the first step in the elucidation of its structure.

Astbury was born in Longton, Stoke-on-Trent. He attended Longton High School and Jesus College, Cambridge. His studies were interrupted by service during the First World War in the Royal Army Medical Corps in Ireland. Astbury then worked with William Bragg, first at University College London and then at the Royal Institution in London.

He was given a lectureship at the University of Leeds in 1928 where he studied the properties of fibrous substances such as keratin and collagen with funding from the textile industry. (Wool is made of keratin.) These substances did not produce sharp patterns of spots like crystals, but the patterns provided physical limits on any proposed structures. Astbury showed that there were differences between stretched and unstretched wool. The data also suggested that that the polypeptide chains in unstretched keratin were coiled helically. A spot in the pattern also showed that the molecular structure repeated every 0.51 nanometres, ie the helix made a complete turn within this distance.

The 0.51 nanometre spacing in keratin was difficult for Astbury to reconcile with a structure. Astbury tried various methods of coiling during 1937 but it was not until thirteen years later that Pauling and Robert Corey were able to propose a structure by using three dimensional molecular models, which they called the 'alpha helix'.

Astbury's worked moved on to X-ray studies of many proteins (including myosin, epidermin and fibrin) and he was able to deduce from the diffraction patterns that the molecules of these substances were coiled and folded. In 1937 Torbjörn Caspersson of Sweden sent him well prepared samples of DNA from calf thymus. The fact that DNA produced a diffraction pattern indicated that it also had a regular structure and it might be feasible to deduce it. Astbury reported that DNA's structure repeated every 2.7 nanometres and that the bases lay flat, stacked, 0.34 nanometres apart. At a symposium in 1938 at Cold Spring Harbor, Astbury pointed out that the 0.34 nanometre spacing was the same as amino acids in polypeptide chains. (The currently accepted value for the spacing of the bases in B-form of DNA is 0.332 nm.)

In 1946 Astbury presented a paper at a symposium in Cambridge in which he said: "Biosynthesis is supremely a question of fitting molecules or parts of molecules against another, and one of the great biological developments of our time is the realisation that probably the most fundamental interaction of all is that between the proteins and the nucleic acids." He also said that the spacing between the nucleotides and the spacing of amino acids in proteins "was not an arithmetical accident".

Astbury's was unable to propose the correct structure of DNA from his rudimentary data. However in 1952 Linus Pauling used Astbury's insufficient data to propose a structure for DNA, which was also incorrect. Nevetheless Astbury's insights led directly to the work of Maurice Wilkins and Rosalind Franklin and from there to the structure of DNA devised by Francis Crick and James D. Watson in 1953.

In later life he was given many awards and honorary degrees. Astbury married Frances Gould in 1922 and they had a son and a daughter.