Protein structural changes in keratin fibers induced by chemical modification using 2-iminothiolane hydrochloride: a Raman spectroscopic investigation.
For the purpose of investigating in detail the influence of chemical modification using 2-iminothiolane hydrochloride (2-IT) on keratin fibers, the structure of cross-sections at various depths of white human hair, treated with 2-IT and then oxidized, was directly analyzed without isolating the cuticle and cortex, using Raman spectroscopy. In particular, the beta-sheet and/or random coil content (beta/R) and the alpha-helix (alpha) content in human hair fibers were estimated by amide I band analysis. The S-S band intensity, amide III (unordered) band intensity, and beta/R content existing from the cuticle region to the center of cortex region of virgin white human hair remarkably increased by performing the chemical modification using 2-IT. On the other hand, not only the S-S band intensity, but also S-O band intensity existing throughout the cortex region of the bleached (damaged) white human hair increased by performing chemical modification using 2-IT. In particular, beta/R content existing throughout the cortex region of the bleached white human hair decreased, while the skeletal C-C stretch (alpha) band intensity at 935 cm(-1) and the alpha content remarkably increased. This indicates a secondary structural change from the random coil form to the alpha-helix form in the proteins existing throughout the cortex region. From these experiments, we concluded that the formation of new disulfide (-SS-) groups resulting from chemical modification using 2-IT induced the secondary structural changes of proteins existing throughout the cortex region.
Kuzuhara
Akio
A
Central Research Laboratories, Mandom Corp., 5-12, Juniken-cho, Chuo-ku, Osaka 540-8530, Japan. kuzuhara-a@mandom.co.jp
D003432:Cross-Linking Reagents / Q000737:chemistry*; D006197:Hair / Q000737:chemistry*; D006200:Hair Color; D006801:Humans; D007096:Imidoesters / Q000737:chemistry*; D007633:Keratins / Q000737:chemistry*; D017433:Protein Structure, Secondary; D013059:Spectrum Analysis, Raman
D003432:Cross-Linking Reagents; D007096:Imidoesters; C005905:methyl 4-mercaptobutyrimidate; D007633:Keratins