"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)
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
Reproduced with permission of the Nature Publishing Group.