Local structure of human hair spatially resolved by sub-micron X-ray beam

Sci Rep. 2015 Nov 30:5:17347. doi: 10.1038/srep17347.

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.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Hair / chemistry*
  • Hair / ultrastructure*
  • Humans
  • Keratins / chemistry
  • Microscopy, Electron, Scanning*
  • Scattering, Small Angle*
  • X-Ray Diffraction*

Substances

  • Keratins