Ceramide binding to African-American hair fibre correlates with resistance to hair breakage.

Repetitive hair-relaxing treatments often applied to African-American hair weaken the hair structure. Therefore hair breakage is a common feature of African-American hair and an important cause of hair loss. Recently, by analysing the lipids extracted from human hair, a fraction of free-ceramide was isolated in which sphinganine was predominant.

Current research on ethnic hair.

This study collected qualitative and quantitative data about the morphology, structure, geometry, water swelling, and mechanical properties of hair fibers from subjects of different ethnic origins. X-ray analysis, cross-sectional measurements, tensile testing, and water swelling were performed on samples of hair collected from Caucasian, Asian, and African subjects. No differences in the intimate structures of fibers were observed among these 3 types of hairs, whereas geometry, mechanical properties, and water swelling differed according to ethnic origin.

A new deformation model of hard alpha-keratin fibers at the nanometer scale: implications for hard alpha-keratin intermediate filament mechanical properties.

The mechanical behavior of human hair fibers is determined by the interactions between keratin proteins structured into microfibrils (hard alpha-keratin intermediate filaments), a protein sulfur-rich matrix (intermediate filaments associated proteins), and water molecules. The structure of the microfibril-matrix assembly has already been fully characterized using electron microscopy and small-angle x-ray scattering on unstressed fibers. However, these results give only a static image of this assembly.

A new approach to the bending properties of hair fibers.

A new test developed to characterize the bending properties of treated or virgin hair fibers is described. The device consists of a pendulum that bends a sample made up of 39 parallel hair fibers at each swinging stroke. Hair bending stiffness can be assessed by the number of strokes observed until the pendulum stops.

Study of the keratinization process in human hair follicle by X-ray microdiffraction.

Synchrotron X-ray micro-diffraction studies along the follicle and the hair fibre allowed us to follow the keratinization process and the progressive organization of the keratin: i) molecular organization appeared progressively in the follicle; the formation of alpha-helices was completed inside the follicle. ii) supramolecular organization appeared only outside the follicle, far from the bulb; filament structure was observed far from the follicle. Comparisons between structures observed for in vitro and in vivo grown hair, whatever in the bulb or in the fibre, indicate there is no evidence of any structural difference.