Attenuated Total Reflection Fourier Transform Infrared Spectroscopy Analysis of Human Hair Fiber Structure

The structure of human hair was studied by attenuated total reflection Fourier transform infrared (ATR-FT-IR) spectroscopy. The use of Ge, ZnSe, and Si internal reflection elements, various incident light angles, and difference spectra allowed detailed analysis of the cuticle, cortex, and cuticle–cortex intercellular regions without physically or mechanically removing the cuticle of the hair fiber. The ATR-FT-IR data showed the cuticle to be composed of protein having predominately beta-sheet and disorder and beta-turn configurations. In contrast, the cortex spectra showed alpha-helical structures due to the presence of intermediate filaments of alpha keratin plus beta-sheet, beta-turn and disorder structures. In the cuticle–cortex interface region the protein structures were primarily disorder and beta-turn with small amounts of beta-sheet configurations. The spectral analyses are consistent with the general information on hair fiber structure proposed in the literature.