The orientation of the alpha-helices in alpha-keratin fibres.
Considerable physical evidence has been accumulated in support of the polarity of alpha-keratin fibres and is summarised here. Dielectric loss and dielectric dipole movement in dry intact fibres as they undergo thermal transition above 200 degrees C show alpha-keratin to be a polar structure. X-ray diffraction has shown that this transition corresponds to the randomisation of the organised alpha-helical structure resulting in the loss of polarity of the fibre. The piezoelectric properties of alpha-keratin can only be explained if its alpha-helical dipoles in the ordered structure alpha-keratin are synergistically aligned in the axial direction. If the alpha-helical units of the IFs of alpha-keratin fibre were in an anti-parallel conformation then dry alpha-keratin would show no polarity. FTIR measurements on alpha-keratin fibres extended in water at 21 and 95 degrees C explain the formation of anti-parallel beta-structures when fibres are extended in steam. Contrary to in vitro experimental data there is clear evidence that native alpha-keratin fibres are polar structures with the alpha-helices aligned in a parallel conformation.
University NSW, NSW, Australia.
Max
M
Feughelman
Donald
D
Lyman
Emory
E
Menefee
Barry
B
Willis
D007633:Keratins / Q000737:chemistry* / Q000648:ultrastructure; D008958:Models, Molecular; D011487:Protein Conformation; D017550:Spectroscopy, Fourier Transform Infrared; D014961:X-Ray Diffraction
D007633:Keratins