"Evidence for the occurrence of the Pauling-Corey alpha-helix in synthetic polypeptides"

Date:
1951-1952
Reference:
PP/CRI/H/1/5
Catalogue details

Licence: In copyright

Credit: "Evidence for the occurrence of the Pauling-Corey alpha-helix in synthetic polypeptides". Source: Wellcome Collection.

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    The University, Glasgow, W.2. 17th December, 1951» Dr. W. Cochran, Crystallographic Laboratory, Cavendish Laboratory, Cambridge. Dear Dr. Cochran and Crick, I wrote my letter of 10th December rather in a hurry, in order not to delay you, and I can see now that although I derived the equations for calculation of structure factors in a general case correctly some weeks ago, the second equation quoted in my addition to your last paragraph is not true. If any long spirals tend to pack with their long axes parallel, they can be not only translated, but also rotated along their axes. My statement should therefore be amplified, for example, by saying, • Then for a translation we have X s ' =- + , and for a rotation round the spiral axis by angle 7? V = 4 - V > so that ' __ -2.7T ¿¿i/L- V) . ^ \ Let j X ( ( 2 T*R ) =Sv,^J It is useful to tabulate or to graph the functions C~ / Sw . Then one can split the expression for T = A in various ways, the choice depending on the method of calculation to be adopted. If a numerical method is to be used, one can write for 2.7T¿/¿. + ^ yj_ ç and A- S eu*)» f + £ $,0 J- /, ¡5 - ¿£ m( 4) - f - , the summation extending over all the spirals. If a graphical method is to be used, one can prepare graphs of c~. t S-^ , from which values can be read after rotating them for any angle.