The Location of the Thioglycolic Acid Molecules in Intrafibrillar Unordered Areas of the Human Hair Keratin Structure

The study investigated the location of thioglycolic acid molecules during the permanent waving process of human hair. Using X-ray diffraction, it was found that these molecules primarily infiltrated the intrafibrillar unordered areas of the hair's keratin structure. This location is where disulphide bonds are most likely to break and reform, which is crucial for maintaining the curled shape of permed hair. The study concluded that the compression stress observed in chemically treated hair, which causes a decrease in the distance between adjacent coils of the α-helix in crystallites, supports the localization of thioglycolic acid in these intrafibrillar areas.