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

Abstract

: 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.

Chemical Reactions Occurring in Curing Treatment for Permanent Hair Straightening Using Thioglycolic and Dithioglycolic Acids

“…(6), which is due to S-S bond fission mechanism, but not due to a direct oxidation of thiol group as eq. (7) [11]. The latter conclusion accords with the one derived from the present result obtained in Table 1.…”

Measurement of Concentrations of Thioglycolic Acid, Dithiodiglycolic Acid and Ammonia in Indoor Air of a Beauty Salon

“…However, TGA was not found even in those samples, probably because it was consumed in the reduction process. According to Ogawa et al (2008), in the reduction step of the permanent waving treatment, the disulfide bond of cysteine residue forms mixed disulfide (KSSK) and cysteine group (KSH) by the reaction with TGA (HSCH 2 COOH) as shown in the following equation,…”

“…The chemical process occurring in perm treatments consisting of hair reduction and subsequent oxidation involves the reactions mainly concerning thiol (SH) and disulfide (SS) 1) . A permanent waving solution (PWS) is commonly used for chemical waving for hair styles, and the major ingredient of PWS is thioglycolic acid (TGA, CAS.…”

“…68-11-1) added as ammonium salt 2) . In the reduction process, TGA works as a reducing agent to cleave the disulfide bonds of cysteine residues in keratin proteins of hair, i.e., cleavage of crosslinks between an intermediate filament and matrix keratin protein (KAP) and between KAP-KAP components 1) . TGA is a colorless and water soluble liquid with 1.3 kPa of vapor pressure at 18°C 3) .…”

<b>Direct Observation of Hair Components Involved in Formation of Permanent Waves</b>

“…It is generally known that the physical, mechanical, and structural properties of hair fibers are changed by permanent waving. For example, permanent waving results in a decrease in the content of microfibrils in hair [8], the α-helixes are changed to random coils in the microfibrils [9][10][11], and the number of disulphide bonds decreases [12].…”