Yasunobu Horiguchi

Structural change of keratin protein in human hair by permanent waving treatment

Abstract The damage to human hair caused by permanent waving treatment was examined from the viewpoint of structure with several spectroscopic methods, 13C CP/MAS n.m.r., wide angle X-ray diffraction (WAXD), FTi.r. and Raman methods. The partial disruption of α-helical structure constituting the microfibril in hair fibre was revealed by this study, although the incomplete re-oxidation of the disulphide bond has been considered to be the main damage caused by the treatment. Moreover, this disruption was mainly caused in the first reduction process. In particular, 13C CP/MAS n.m.r. gave the quantitative evaluation for change of α-helical content in the microfibril with permanent waving treatment. In addition, FTi.r. and Raman spectra indicated that the α-helix was partially changed to random coil, rather than to β-sheet structure.

Carbon-13 n.m.r. studies of keratin intermediate filament of human hair

Abstract 13C n.m.r. spectra of low sulfur fraction in S-(carboxymethyl) keratine, (SCMKA), which corresponds to the hard keratin intermediate filament (KIF) in human hair were observed in aqueous solution. The spectra were compared with those of SCMKA in 8 M urea and high sulfur fraction in S-(carboxymetyl) keratine, (SCMKB), in aqueous solution. The circular dichroism spectrum of SCMKA indicated 40% α-helix in the aqueous solution, and changed to that of random coil in 8 M urea. The SCMKB in aqueous solution also took random coil. The observed peaks in the 13C n.m.r. spectra of SCMKA in aqueous solution come mainly from the amino acid residues such as Thr, Ser, Pro and Gly in the N- and C-terminal domains with random coil structure. Thus it is suggested that these domains had high mobility. However, the amino acid residues, Leu, Ile, Glu, Arg and Lys, in the rod domain give essentially no peaks because of very restricted motion of the chain with coiled-coil structure.