Abstract
In order to investigate in detail the internal structure changes in virgin black human hair keratin fibers resulting from bleaching treatments, the structure of cross-sections at various depths of black human hair, which had been impossible to analyze due to high melanin granule content, was directly analyzed using Raman spectroscopy. The gauche-gauche-gauche (GGG) content of the -SS- groups existing from the cuticle region to the center of cortex region of the virgin black human hair remarkably decreased, while the gauche-gauche-trans (GGT) and trans- gauche-trans (TGT) contents were not changed by performing the excessive bleaching treatment. In particular, it was found that not only the β-sheet and/or random coil content, but also the α-helix content existing throughout the cortex region of virgin black human hair decreased. In addition, the transmission electron microscope observation showed that the proteins in the cell membrane complex, the cuticle and cortex of the virgin black human hair were remarkably eluted by performing the excessive bleaching treatment. From these experiments, it can be concluded that the -SS- groups, which have a GGG conformation, decomposed and finally converted to cysteic acid, and the α-helix structure of some of the proteins existing in the keratin changed to the random coil structure, or was eluted from the cortex region, thereby leading to the change to the rough structure of the virgin black human hair after the excessive bleaching treatment.
