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The Francis Crick Papers

"Evidence for the Pauling-Corey alpha-Helix in Synthetic Polypeptides" [Editorial letter] pdf (166,259 Bytes) ocr (1,354 Bytes)
"Evidence for the Pauling-Corey alpha-Helix in Synthetic Polypeptides" [Editorial letter]
In this letter to the editors of Nature, Crick and William Cochran previewed calculations, published in greater detail shortly thereafter, that enabled them to predict the X-ray diffraction pattern produced by a crystal with a helical shape whose atoms are arranged at regular intervals along its axis. Their theory stated that for crystals with a helical shape, the X-ray pattern can be calculated by a combination of "Bessel functions," which arise in structures of cylindrical symmetry, such as a helix. Their calculations supported Linus Pauling and Robert Corey's finding that many polypeptides, molecules that consist of a sequence of amino acids, including most proteins, are in the shape of a single-stranded helix, which Pauling and Corey dubbed the alpha helix. Having provided mathematical proof that specific two-dimensional X-ray diffraction patterns reflect the three-dimensional shape of a helix later made it easier for Crick to discern that X-ray images of DNA fibers taken by Rosalind Franklin revealed the helical structure of DNA and the ladder spacing of its nitrogenous bases, because these images conformed to Crick's and Cochran's calculations.
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1952-02-09 (February 9, 1952)
Cochran, William
Crick, Francis
Periodical: Cochran, William, and Francis Crick. "Evidence for the Pauling-Corey alpha-Helix in Synthetic Polypeptides" [Editorial letter]. Nature 169, 4293 (9 February 1952): 234-235. Article. Letter (correspondence). 2 Images.
Nature Publishing Group
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