No abstract

The outermost protein layer of wool cuticle cells is known as the exocuticle a-layer. This layer is a resistant barrier to the degradation of the fibre and, as a result, little is known of its proteinaceous composition. Merino wool fibres were subjected to both proteolytic and chemical digestion and the resulting material was found by transmission electron microscopy to be highly enriched in a-layer. Amino acid analysis revealed a high cysteine and glycine content, with a close, but not exact, match to the Allwörden membrane. Subsequent digestion of the a-layer preparation by 2-nitro-5-thiocyano-benzoic acid produced a large number of short peptides, and analysis by mass spectrometry revealed peptides with strong homologies to cuticular ultra-high sulphur proteins of sheep wool and cuticular ultra-high and high-sulphur proteins of human hair, thus supporting other evidence for the presence of these sulphur-rich proteins in the a-layer.

No abstract

Hair curvature underpins structural diversity and function in mammalian coats, but what causes curl in keratin hair fibres? To obtain structural data to determine one aspect of this question, we used confocal microscopy to provide measurements of the two cell types that make up the cortex of merino wool fibres, which waschosen as a well-characterised model system representative of narrow diameter hairs, such as underhairs. We measured orthocortical and paracortical cross-sectional areas, and cortical cell lengths, within individual fibre snippets of defined uniplanar curvature. This allowed a direct test of two long-standing theories of the mechanism of curvature in hairs. We found evidence contradicting the theory that curvature results from there being more cells on the side of the fibre closest to the outside, or convex edge, of curvature. In all cases, the orthocortical cells close to the outside of curvature were longer than paracortical cells close to the inside of the curvature, which supports the theory that curvature is underpinned by differences in cell type length. However, the latter theory also implies that, for all fibres, curvature should correlate with the proportions of orthocortical and paracortical cells, and we found no evidence for this. In merino wool, it appears that the absolute length of cells of each type and proportion of cells varies from fibre to fibre, and only the difference between the length of the two cell types is important. Implications for curvature in higher diameter hairs, such as guard hairs and those on the human scalp, are discussed.

This study validates the utility and power of redox proteomic-based approaches to characterizing hair modification. This offers potential application to a wide range of damage types, as well as evaluation of new damage mitigation and repair technologies.