Structure Of α-Keratin Research Articles

The structure of α-keratin

A model for the structural arrangements of the protein chains in α-keratin has been proposed on the basis of the diffraction pattern of porcupine quill tips. The model implies that the protein chains are basically of the α-helix configuration but are supercoiled and packed in five concentric layers. The supercoiling in the different layers makes one turn in 198 Å along the axis of the tonofilament. The number of chains in the different layers are 3, 7, 10, 16, and 19. This arrangement that is based on the diffraction pattern gives a diameter of the tonofilament that is in agreement with electron microscopic data.

Structure of alpha-keratin.

Structure of alpha-keratin.

Part II: The Densities of Native Keratins

An apparatus for rapid density determinations is described in which small keratin samples may be dried and anhydrous solvent subsequently distilled onto them, the density being measured by finding the temperature at which the sample neither floats nor sinks. Densities of a representative series of keratins are reported and used to assess relative crystallinity. The measured densities are compared with those predicted by various models of α-keratin structure.

Models of α-keratin structure

Models of α-keratin structure

On the Structures of Fibrous Proteins. I. A New Polypeptide Structure of α-Keratin

On the Structures of Fibrous Proteins. I. A New Polypeptide Structure of α-Keratin

Stable configurations of a polypeptide chain.

IN recent communications in Nature, Ambrose and his co-workers proposed a model for the molecular structure of α-keratin based on their measurements with polarized infra-red radiation1,2. The same model has already been presented by two of us (S. and M.) in 1947, based on the energy consideration for the intramolecular rotation3,4.

Denaturation in Regenerated Protein Fibres

IN a discussion on the possibility of producing a regenerated keratin fibre, Mercer1 claims to have retained the α-form of the molecule in wool reconstituted from solution. This is a matter of some interest, as the yarns produced by Dr. R. L. Wormell2 and myself show no evidence of the α-keratin structure even in orientated fibres. During the past few months, highly orientated specimens of casein yarn have been made3 which may throw some light on Mercer's results, especially with reference to the type of solution from which fibres are drawn containing an α-keratin phase. Fig. 1 is an X-ray photograph of a Ferretti-type casein fibre which shows little or no obvious orientation by X-rays. Fig. 2 is an X-ray photograph of highly orientated casein which is, in the main, made up of reflexions from a two-phase system. First there is the X-ray photograph of a normal β-protein type of fibre comprising an axial repeat of 3·25 A., a backbone spacing of 4·65 A., and a side-chain spacing of approximately 10·5 A. Superimposed on this diagram, however, there is a strong polar arc of 4·65 A., which is most probably indicative of a protein phase containing a crystalline cross β-configuration of the molecule.