Intermolecular Disulfide Cross-Linked Structural Change Induced by Permanent Wave Treatment of Human Hair with Thioglycolic Acid

The study investigated the structural changes in human hair induced by permanent wave treatment using thioglycolic acid (TGA) and sodium bromate. By applying rubber elasticity theory to the force-extension curves of treated hair fibers, researchers identified key structural parameters, including the number of intermolecular disulfide (SS) bonds in intermediate filament (IF) proteins, the volume fraction of matrix protein, and the shape of the matrix domain. The findings revealed that TGA preferentially attacked SS bonds between globular matrix proteins over those between IF proteins, leading to a shape change in the matrix domain from ellipsoidal to near-spherical.