London: Macmillan, 1952. 1st Edition. FIRST EDITION IN ORIGINAL WRAPS of Francis Crick's and William Cochran's letter to the editors of Nature in which they previewed the important calculations 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 lent strong support to 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 and Cochran's calculations (Profiles in Science, National Library of Medicine, Crick Papers). Item #301
CONDITION & DETAILS: London: Macmillan & Co., Ltd. Volume 169, No. 4293. Original Wraps. (10 x 7 inches; 250 x 175mm). Original paper wraps. Ex-libris: bearing only a very faint stamp on the front wraps. Near fine condition in every way.