Characteristic Microstructure of Curved Human Hair

The study investigated the microstructure of curved human hair and found significant differences between the convex and concave sides. Fluorescein isothiocyanate permeated faster on the convex side, indicating structural differences. Transmission electron microscopy (TEM) showed smaller, dispersed macrofibrils on the convex side and larger, fused macrofibrils on the concave side. The alignment of intermediate filaments was helical on the convex side and parallel on the concave side. Amino acid analysis revealed lower Cys and higher Asp, Glu, and Gly on the convex side. These findings suggest similarities to the structure of ortho- and para-cortical cells in wool fibers, indicating a universal structure in curved mammalian hair.