Action of Thioglycolic Acid and L-Cysteine to Disulfide Cross-Links in Hair Fibers during Permanent Waving Treatment

摘要

Reactions occurring during permanent waving (perm) treatment of hair reduction and subsequent oxidation were studied by using FT-IR technique and a polarographic method to estimate the contents of cysteic acid, intermediate cystine oxides, thiol, and disulfide (SS) groups in the perm hairs. The reducing agents used were thioglycolic acid (TGA) and L-cysteine (CyS). The perm hair samples were prepared by repeating from one to five times of reduction-oxidation treatment. The difference in the fluorescence activity, SS bond reduction, FT-IR spectra, waving efficiency, and stress-strain properties between the samples obtained by the reduction systems with TGA and CyS has been discussed. It was found that the SS contents of the samples from both systems were decreased in approximately similar order with the increase of the number of times of treatment and the decrease in the SS groups was due to the conversion wholly into cysteic acid via the cleavage of SS bond through the S-S fission mechanism and partly into free cysteine groups. It was presumed, further, that TGA attacks the cross-links between the intermediate filament (IF) and the matrix protein (KAP), and between KAP-KAP component proteins, whereas CyS attacks the SS cross-links associated with the non-helical segments of IF acting as a KAP component, and that the reduction sites of SS cross-links in microstructure of hair relate the waving efficiency of perm hair.