Low-angle X-ray diffraction studies of the effect of extension on macromolecular organisation in keratin

Abstract

The low-angle X-ray diffraction patterns of Lincoln wool fibres stained with AgNO 3 before and after stretching in water have been studied. Changes in the Bragg spacings of the equatorial reflections have been related to dimensional changes in the matrix and microfibrils and have indicated that neither histological component extends at constant density unless all of the disulphide bonds are broken prior to stretching and the incorporation of silver. These results were found to be in accord with qualitative changes observed in the meridional patterns, and intensity changes in the 25 Å halo. A study of the changes in spacing of the 25 Å halo has also revealed that the effect of extension on the matrix is largely one of molecular orientation and not stretching. The conclusions reached are related to a recently derived structural model for α-keratin.