Search

Curvature in mammalian fibers, such as wool and human hair, is an important feature of the functional trait of coat structure—it affects mechanical resilience and thermo‐insulation. However, to examine the relationship between fiber curvature, ultrastructure and protein composition fiber diameter variability has to be minimal. To achieve this we utilised the progeny of straight‐wool domestic sheep mutant rams (crimp mutants) and wild‐type ewes. Proteomic and structural results of the resulting mutant/wild‐type twin pairs confirmed that straight crimp mutant wool had a normal cuticle and the same cortical protein and ultrastructural building blocks as wild‐type (crimpy) fibers but differed in the layout of its cortical cells and in the relative proportions of keratin (K) and keratin‐associated proteins (KAPs). In the case of the crimp mutants (straight fibers), the orthocortex was distributed in a fragmented, annular ring, with some orthocortical cells near the central medulla, a pattern similar to that of straight hairs from humans and other mammals. Crimp mutant fibers were noted for the reduced abundance of some proteins in the high glycine–tyrosine class normally associated with the orthocortex, specifically the KAP6, KAP7, and KAP8 families, while proteins from the KAP16 and KAP19 were found in increased abundance. In addition to this, the type I keratin, K38, which is also associated with the orthocortex, was also found at lower abundance in the mutant fibers. Conversely, proteins from the ultra‐high sulfur class normally associated with the paracortex, specifically the KAP4 and KAP9 families, were found in higher abundance. [ABSTRACT FROM AUTHOR]

We do not know what causes natural-born curliness in human scalp hair or in the hair of mammals in general. This brief review describes why hair curls, and the cause of the phenomenon is more complex than often appreciated. We then briefly review features that are associated, correlated, or purportedly cause hair curl. [ABSTRACT FROM AUTHOR]

The sensation of prickle from textile garments is directly related to the force that a fiber protruding from the fabric surface can exert on the skin without buckling – its critical buckling load (CBL). Finite element modeling (FEM) has previously been used in the literature to predict CBLs for a set of 25 fibers with different along-fiber morphology. With a view to high-throughput analysis of fibers, we investigated two analytical methods that were potentially faster and less computationally intensive than FEM and applied them to calculate CBLs for the same set of fibers. In addition, we tested a numerical integration and gradient search (NIGS) method that we developed by adapting a previously published, non-FEM, numerical approach.The analytical methods that we tested were either inadequately formulated or prone to instability. Our NIGS method was more reliable that the analytical methods (but slower to compute), and its results appeared more accurate than the published FEM results, based on an inconsistency metric that we developed.The published FEM results and the NIGS predictions agreed within 5% for 60% of the fibers, and within 10% for 72% of the fibers (with differences ranging from 0.4% to 19.1%) and generally showed qualitative agreement on the response of CBL to fiber shape, with some notable exceptions.The response of CBL to dimensional variation was complex. This, and the inconsistency between methods, highlights the need for caution when analyzing complicated biological structures, such as wool, and the value of verifying the reliability of any predictions from any approach. [ABSTRACT FROM AUTHOR]

Two of the present authors have presented a model for macrofibril template self-assembly which is based on a concerted process of sudden, delayed, short filament formation with immediate phase transfer to a lyotropic liquid crystal (mesophase). In recent years, information on the spatio-temporal patterns of keratin protein expression within wool follicles has come to hand, and we here report some recently acquired important information in this area. If the "mesophase model" is to remain credible it must be compatible with the spatio-temporal patterns of keratin expression. This paper explores the match between the mesophase model and patterns of protein expression, and concludes that they are broadly consistent. At present the model does not extend to keratin associated protein (KAP) expression. The model is also particularly successful in explaining macrofibril structural features in different cell types. [ABSTRACT FROM AUTHOR]

Protein oxidative degradation is implicated in a wide range of deleterious effects. For human hair, this oxidative damage can lead to significant observable changes in fiber physical and visual properties. A redox proteomic approach was applied to map molecular modification in human hair proteins and correlate this modification with the abundance of copper ( II) ions, the levels of UV exposure and the general level of hair pigmentation. An increase in oxidative modification was observed with increasing copper ( II) ion levels, regardless of the pigmentation level. Significantly, increased protein oxidative modification was also observed to occur in both lightly and darkly pigmented hair tresses even in the absence of irradiation, albeit at lower relative levels. Modification levels increased with increased copper ( II) ion concentration. This new finding indicates that the level of copper ( II) ions in human hair plays a key role in mediating protein oxidation, with or without exposure to UV light. Overall, these results strongly suggest that minimization of the level of copper ( II) ions in human hair will mitigate and/or slow protein oxidative modification and therefore lower overall hair damage. [ABSTRACT FROM AUTHOR]