Keratin disulfide bond

Keratin disulfide bonds are covalent cross-links formed between the sulfur atoms of two cysteine residues within or between keratin polypeptide chains in the hair shaft (Source: NIH StatPearls, Anatomy, Hair). These bonds are the primary determinants of the hair's mechanical strength, resilience, and permanent shape, such as curliness or straightness (Source: Robbins, C. R., Chemical and Physical Behavior of Human Hair). In the context of pharmacology and cosmetology, these bonds are targeted by reducing agents like ammonium thioglycolate to break the bridges, allowing the hair to be reshaped before being re-oxidized to lock in a new form (Source: PubChem, Thioglycolic acid). Additionally, modern bond-building treatments utilize maleate-based compounds to bridge broken disulfide bonds, restoring the structural integrity of hair damaged by heat or chemical processing (Source: International Journal of Cosmetic Science). Genetic defects affecting the formation or density of these bonds can result in clinical conditions like trichothiodystrophy, characterized by brittle hair and systemic abnormalities (Source: National Library of Medicine, Genetics Home Reference).

Other names

Cystine bridgeDisulfide bridgeS-S bondKeratin cross-linkCystine linkage

Reduction of disulfide bonds to thiols (cysteine) to allow structural reshaping, followed by oxidation to reform bonds; or covalent cross-linking of broken sulfur-sulfur bridges to restore fiber strength.