Presence of a Δ⁵-Unsaturated Sterol Derivative in the Medulla Cells of Keratin Fibres

Abstract

KERATIN differs from other scleroproteins in containing a relatively high percentage of sulphur, and it is known that the sensitivity of wool and hair to attack by alkali and alkaline reducing agents results from fission of the cystine disulphide linkages, followed, under more drastic conditions of treatment, by hydrolysis of peptide linkages^1,2. The medulla of sheep wool and porcupine quill, however, is devoid of cystine³, while the medulla cells of goat hair resist hydrolysis by 4N sodium hydroxide at room temperature, and contain little, if any, sulphur⁴. This observation has been extended to hair from several carnivores and rodents^5,6, and would appear to be a general property of medullary keratin. The X-ray diffraction pattern of medulla cells dissected from Canadian porcupine quill reveals the presence in the cells of?-keratin, together with unidentified material⁷. On X-ray examination, medulla cells isolated from hair by treatment with cold sodium hydroxide showed no spacing corresponding to?-keratin ; but a strong meridional arc was found, identical with that from the non-protein constituent of porcupine quill medulla cells⁷.