The Structure of Keratin 



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Fig. 1. Cortical ceil isolated from Australian merino wool and exposed to ultrasonic vibrations, in uater. for 12 hours. 

 Magnification 10,000. 



Fig. 2. Cortical cell isolated from Lincoln wool and exposed to ultrasonic vibrations, in water, lor 12 hours. 

 Magnification 29,000. 



Fig. 3. Cortical cell isolated from Lincoln wool and exposed to ultrasonic vibrations, in lithium bromide solution, for 

 4 hours. Magnification 21,000. 



Fig. 4. Fragment of cortical cell isolated from Lincoln wool and exposed to ultrasonic \ibrations, in lithium bromide 

 solution, for 4 hours. Magnification 32,000. 



differences in the type of packing of the microfibrils 

 in cortical cells of the two regions: ortho- and para- 

 cortex. The type of lateral packing of the micro- 

 fibrils must influence many properties of keratin 

 fibres. We have discussed this problem in some 

 detail in connection with our proposed mechanism 

 of supercontraction in keratin (7) and have further 

 suggested (14) that keratinization involves the stabi- 

 lization of microfibrillar texture leading to the 

 uniplanar cross-linking together of the microfibrils 

 to form sheets. 



However, Fraser (4) and, independently, Rogers 

 (private communication) suggested that the width 

 ( 1 to 3 microns) of the sheets of microfibrils obtained 

 by us (6, 7) may be rather due to the mode of bio- 

 synthesis of macrofibrils; namely some "early" mi- 

 crofibrils aggregating laterally, and their continuing 

 to be synthesized in scroll-like fashion to form 

 macro-fibrils. They, in fact, suggested that the 

 chemical treatment of Jeffrey et al. (6, 7) was capable 



of reversing this underlying organization in the fully 

 hardened keratin. 



This divergence o'i views ma\ be accounted for 

 by the differences in chemical reactivity between 

 the cortical cells from crimpy and straight animal 

 fibres; a view confirmed recently by Satlow and 

 Sikorski (13) who found that more resistant 

 cortical cells show a more complex structure. 

 This lends support to the observation of Rogers 

 (12) that the intact cortical cells were apparent 

 in the para-cortex of crimpy fully hardened and 

 oxidi/cd keratin fibres, whereas macrofibrils were 

 evident in the ortho-cortex. 



it must be admitted that the thickness of micro- 

 fibrillar sheets observed in our experiments (6) can 

 account only for a relatively small fraction of the 

 diameter of cortical cells. We have, therefore, de- 

 cided to re-examine this question in some detail and, 

 in our experiments, used cortical cells which have 

 been separated with the minimum of damage. How- 



