In this letter Crick pays tribute to the crystallographer and political activist J. Desmond Bernal, called Sage by his friends because of his reputation as a polymath. In the early 1930s Bernal had pioneered the use of X-ray diffraction techniques in elucidating the structure of biologically significant macromolecules such as proteins, at the time an undertaking of almost insurmountable complexity. The crystallographers and Nobel Laureates Max Perutz and Dorothy Hodgkin, mentioned by Crick, studied with Bernal at Cambridge University in the 1930s and were his most famous disciples. Rosalind Franklin found an enthusiastic supporter in Bernal, whose laboratory at Birkbeck College she joined in 1953. Crick himself had applied for a research position there in 1947, but was rebuffed by Bernal's secretary with the words, "Do you realize that people from all over the world want to come to work with the professor? Why do you think he would take you on?". Crick's reference to "unkind things" he said about protein crystallography at an early age in his career was to a research seminar he had given at the Cavendish Laboratory in 1950, when Crick was a doctoral student under Perutz. There, in the presence of the Cavendish professor, Sir William Bragg, Crick brashly dismissed several of the methods commonly used by protein crystallographers, including Patterson functions, as unlikely to yield a three-dimensional picture of the electron density of a protein crystal, without which the location of the thousands of atoms in the crystal could not be known. The only method of which Crick approved was the so-called isomorphic replacement method, which came to dominate the field. Bragg did not view Crick's criticism kindly, and accused him of "rocking the boat.". The article Crick sent along with his letter was "The Origin of the Genetic Code," published in the Journal of Molecular Biology, vol. 38 (1968), pp. 367-79.
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