Evidence for the Pauling–Corey α-Helix in Synthetic Polypeptides

Abstract

WE have calculated, in collaboration with Dr. V. Vand¹, the Fourier transform (or continuous structure factor) of an atom repeated at regular intervals on an infinite helix. The properties of the transform are such that it will usually be possible to predict the general character of X-ray scattering by any structure based on a regular succession of similar groups of atoms arranged in a helical manner. In particular, the type of X-ray diffraction picture given by the synthetic polypeptide poly-γ-methyl-L-glutamate, which has been prepared in a highly crystalline form by Dr. C. H. Bamford and his colleagues in the Research Laboratories, Courtaulds, Ltd., Maidenhead, is so readily explained on this basis as to leave little doubt that the Pauling–Corey α-helix², or some close approximation to it, exists in this polypeptide. Pauling and Corey² have already shown this correspondence in the equatorial plane; it is shown here that the correspondence extends over the whole of the diffraction pattern.