Internal Structure Changes in Bleached Black Human Hair Resulting from Chemical Treatments: A Raman Spectroscopic Investigation

In a study from November 2014, researchers used Raman spectroscopy to analyze the internal structure of excessively bleached black human hair fibers that had undergone a permanent waving process. They discovered that the treatment with l-cysteine (CYS) primarily reacted with the gauche-gauche-gauche (GGG) conformation of disulfide bonds in the hair keratin, leading to a significant decrease in both GGG and cysteic acid content throughout the cortex after oxidation following reduction. Additionally, the oxidation process after reduction and hydrolyzed eggwhite protein (HEWP) treatment increased GGG content and decreased trans-gauche-trans (TGT) content. The study concluded that keratin associated protein (KAP), which is rich in disulfide bonds, was lost from the cortex due to the breaking of these bonds, reducing the reconnection of disulfide bonds after chemical treatments. Furthermore, HEWP treatment was found to aid in the reconstruction of KAP, enhancing the reconnection of disulfide bonds during the oxidation process.