An x-ray diffraction study of thermally-induced structural changes in alpha-keratin.
A series of events takes place as wool is heated under vacuum from room temperature to 250 degrees C: Loosely and strongly bound water molecules are removed at temperature at and below 150 degrees C; a glass transition of the amorphous keratin occurs at 160-175 degrees C; helices melt at 215 and 235 degrees C. The structural changes take place between the glass transition and the helix melting temperature  are observed as reflected in the low-angle X-ray diffraction patterns: The 39 A meridional reflection is intensified; a 4-point diagram at azimuthal angle of 45 degree with spacing around 46 A appears; the intensity of the 33 A meridional reflection decreases, and the 66 A meridional reflection is the most heat-resistant.
D000818:Animals; D055598:Chemical Phenomena; D002621:Chemistry; D007633:Keratins; D011487:Protein Conformation; D011489:Protein Denaturation; D013696:Temperature; D014935:Wool; D014961:X-Ray Diffraction
D007633:Keratins