Epidermin oriented

The d structure produced by the thermal contraction of intact epidermis, or of isolated epidermin, is unusual and to be distinguished from the normal parallel d form produced by stretching, where the main chains lie parallel to the axis of stretching. If thermally contracted material is stretched 80-100% and dried, the d pattern is oriented so as to show that the main chains lie for the most part across the axis of the fiber i.e. at right angles to the direction of stretching. The diffraction pattern is here referred to as cross d (49). 

Fig. 14. Infrared absorption spectra of films of epidermin. A, stretched (200% extension from east film), a-form. B, same as A but contracted by 42% in cold water lesser orientation of a-form. C, partial conversion to -form by high extension in saturated ammonium sulfate. ------ Electric vector parallel to axis of orientation. ------ Electric vector perpendicular to axis of orientation.

A number of infrared absorption studies on the purified epidermal protein are described. In combination with the X-ray diffraction data, they entirely confirm the recent advances in the definition of absorption spectra, which are characteristic of a- and /3-type proteins and polypeptides, in terms of the kinds of dichroism and the frequency changes associated with the (3 form. It is pointed out that as the dichroism changes with the a — change it is not possible to read off the relative amounts of a and from the absorption spectra because of the differences in the orientation of the absorbing bonds with reference to the plane of the film. In the absorption spectra of highly stretched epidermin, where... 

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