title: Local structure of human hair spatially resolved by sub-micron X-ray beam.
abstract: Human hair has three main regions, the medulla, the cortex, and the cuticle. An existing model for the cortex suggests that the α-keratin- based intermediate filaments (IFs) align with the hair's axis, but are orientationally disordered in-plane. We found that there is a new region in the cortex near the cuticle's boundary in which the IFs are aligned with the hair's axis, but additionally, they are orientationally ordered in-plane due to the presence of the cuticle/hair boundary. Further into the cortex, the IF arrangement becomes disordered, eventually losing all in-plane orientation. We also find that in the cuticle, a key diffraction feature is absent, indicating the presence of the β-keratin rather than that of the α-keratin phase. This is direct structural evidence that the cuticle contains β-keratin sheets. This work highlights the importance of using a sub-micron x-ray beam to unravel the structures of poorly ordered, multi-phase systems.
authors.affiliation: Brazilian Synchrotron Light Source, CNPEM, SP 13083-970, Brazil.
authors.forename: Vesna
authors.initials: V
authors.lastname: Stanić
authors.affiliation: Brazilian National Nanotechnology Laboratory, CNPEM, SP 13083-970, Brazil.
authors.forename: Jefferson
authors.initials: J
authors.lastname: Bettini
authors.affiliation: Brazilian National Nanotechnology Laboratory, CNPEM, SP 13083-970, Brazil.
authors.forename: Fabiano Emmanuel
authors.initials: FE
authors.lastname: Montoro
authors.affiliation: Center for Functional Nanomaterials, Brookhaven National Laboratory, Upton, NY 11973, USA.
authors.forename: Aaron
authors.initials: A
authors.lastname: Stein
authors.affiliation: National Synchrotron Light Source, Brookhaven National Laboratory, Upton, NY 11973, USA.
authors.forename: Kenneth
authors.initials: K
authors.lastname: Evans-Lutterodt
mesh_terms: D006197:Hair / Q000737:chemistry* / Q000648:ultrastructure*; D006801:Humans; D007633:Keratins / Q000737:chemistry; D008855:Microscopy, Electron, Scanning; D053838:Scattering, Small Angle; D014961:X-Ray Diffraction
chemical_list: D007633:Keratins