Helical conformations of polypeptide chains

Abstract

It is shown in this paper, how simple polypeptide helices for all possible orientations of the peptide residue with respect to the helical axis can be obtained by the method of cyclographic projection. The cyclographic projection is actually applied to three cases and the results are described. It is also shown that the celebrated α helix and the other helices, described so far, are particular cases of slightly more general ones. So also it is found that the extended β structure, and the pleated sheet structure of Pauling and Corey, are also particular cases of a range of structures possible, in which every alternate residue has the same orientation (i.e., digonal helices with two residues per turn). The method described here can also be used to find out the co-ordinates of atoms when the elements of a helical structure are known from other data.