Combining a submicron X-ray beam with cross-section geometry, a team of researchers in Brazil and New York has detected new structural features of human hair, describing their discovery and methods during the American Crystallographic Association (ACA) 2015 Meeting this week (25-29 July).
The work “provides irrefutable experimental evidence of the hair phase variation across the three main regions of hair and is an important step toward gaining a better understanding of hierarchical ordering of the intermediate filaments of keratin,” says Vesna Stanic, a scientist working at the Brazilian Synchrotron Light Source.
“It also highlights the importance of using a submicron X-ray beam to unravel the structures of poorly ordered, multiphase systems such as hair.”
According to the research team, the findings will be of great benefit to the cosmetics industry and aid product development.
“If the goal of the cosmetics industry is to make new and better products for hair, then it’s absolutely critical for them to understand the local structure of hair and the effects their products are having at the molecular level,” adds Stanic.
The discovery
To build on previous studies on diffraction patterns and hair treatments, Stanic and her team used x-ray diffraction patterns to reveal the local arrangement of molecular and atomic structure, by measuring it with an X-ray beam aimed parallel, rather than perpendicular to the hair axis.
“I wanted to use a submicron X-ray beam, so I asked colleague Kenneth Evans-Lutterodt to perform an experiment on the microdiffraction beamline at Brookhaven National Laboratory,” continues Stanic.
So, using a submicron X-ray beam and transmission electron microscopy, the team were able to spatially resolve the local structure of the three main regions of human hair: medulla, cortex and cuticle, finding an additional, previously unobserved structural region in the cortex near the cuticle boundary.
“We also discovered that within the cuticle a key diffraction feature of the alpha keratin is absent -- indicating the presence of beta keratin instead of the alpha keratin phase,” says Stanic. Until now, it was believed that keratin in the whole hair had only an alpha conformation, she explains.