In 1950, Bragg, Kendrew and Perutz published "Polypeptide chain configurations in crystalline proteins" (open access) and were famously 'proved wrong' by Pauling, Corey and Branson the following year, in the paper that documented the alpha and gamma helices, "Two Hydrogen-Bonded Helical Configurations of the Polypeptide Chain" (also OA)
I'm reading about this (as reviewed here for example) where the idea is that Bragg et al were disproved - in the words of the Pauling paper:
None of these authors propose either our 3.7-residue [α] helix or our 5.1- residue [γ] helix. On the other hand, we would eliminate by our basic postulates all of the structures proposed by them. The reason for the difference in results obtained by other investigators and by us through essentially similar arguments is that both Bragg and his collaborators . . . discussed in detail only helical structures with an integral number of residues per turn, and moreover assume only a rough approximation to the requirements about interatomic distances bond angles, and planarity of the conjugated amide group, as given by our investigations of simpler substances. We contend that these stereochemical features must be very closely retained in stable configurations of polypeptide chains in proteins, and that there is no special stability associated with an integral number of residues per turn in the helical molecule.
There was one however, the 310 helix which was correctly identified by Perutz's group in 1950. I don't have any access to library facilities at present and online resources aren't quite the same as a solid textbook. I'm wondering if any of the other forms described were in fact correct?
To list, these were:
- ( 310 )
I'll continue looking in the meantime but it's hard to search when there are subscripts in names, and I would think more experienced protein scientists could give me a quicker answer (or just direct me to where I should be reading)