Abstract
Brown human hair was bleached three times (45 min × 3) and four times (45 min × 3 + 15 min) with commercial formulations containing persulfate salts and hydrogen peroxide. The hair samples were characterized by Raman and IR spectroscopy in the Attenuated Total Reflectance (ATR) mode to gain more insights into the possible secondary structure and C(α)-C(β)-S-S-C(β)-C(α) conformational changes induced by bleaching. The latter were evaluated through band-fitting procedures; the relative content of the disulfide bridges and oxidized sulfur species (cysteic acid, Bunte salt, cystine oxides) was assessed. The observed conformational changes could be significant in developing restoring agents to be used after hair decoloration. The use of two different spectroscopic techniques allowed to discriminate the information coming from the cortical region of hair (Raman) and the cuticle (ATR/IR). This article refers to "Structural investigation on damaged hair keratin treated with α,β-unsaturated Michael acceptors used as repairing agents" (Di Foggia et al., Int. J. Biol. Macromol. 167 (2021) 620-632 https://doi.org/10.1016/j.ijbiomac.2020.11.194).