Crosslinking Structure of Keratin: Number and Type of Crosslinks in Microstructures of Untreated and Potassium Cyanide Treated Human Hair

The study investigated the crosslinking structure of keratin in human hair, focusing on the effects of potassium cyanide (KCN) treatment. It was found that KCN selectively converted disulfide (SS) bonds to monosulfide (S) crosslinks. The treated hair exhibited rubberlike elasticity when swollen with a specific solution. Analysis showed that SS to S conversion occurred first in low-sulfur (LS) proteins, while high-sulfur (HS) proteins' SS bonds converted faster from intermolecular to intramolecular bonds. The intact hair's crosslink percentages were determined, with LS proteins having 27.0% intermolecular SS, 39.0% intermolecular X, and 34.0% intramolecular SS + X links, and HS proteins having 11.9% intermolecular SS and 88.1% intramolecular SS links. The total crosslinks in hair were 627 μmol/g, with LS and HS proteins contributing 13.8% and 86.2%, respectively.