Analysis of structural change in keratin fibers resulting from chemical treatments using Raman spectroscopy

Abstract

In order to investigate the influence of chemical treatments (reduction, heating, and oxidation) on keratin fibers, the structure of virgin white human hair resulting from a permanent hair straightening process at various depths of cross-sectional samples was directly analyzed without isolating the cuticle and cortex, using Raman spectroscopy. The band shape of the cuticle was different from that of the cortex, and the cuticle had a more amorphous structure, compared with the cortex. The S-S band intensity existing in the hair surface remarkably decreased, while the S-S band intensity in the hair center was not changed by performing the reduction process. In the case of heating the keratin fibers after the reduction process, this tendency was unchanged. On the other hand, the amide III (unordered) band intensity in the cortex region increased, indicating that proteins existing throughout the cortex region caused a change to the random coil form. Moreover, approximately 95% of the disconnected -SS- groups were clearly reconnected by performing the oxidation process after heating (the degree of reconnection of -SS- groups was about 90%, in the case of oxidizing after reduction). From these experiments, we concluded that the heat treatment process in the permanent hair straightening treatment caused the randomization of proteins existing throughout the cortex region, thereby contributing to the acceleration of the reconnection of -SS- groups during the oxidation process.

Molecular characterization of reconstructed skin model by Raman microspectroscopy: Comparison with excised human skin

“…[48][49][50] This peak is absent in normal epidermis spectra, which reinforces the conclusion about the sensitivity of Episkin toward oxidative mechanisms.…”

“…The same conclusion is given from the amide III band analysis (the peak at 1283 cm 21 (a helix) is more intense than the one at 1250 cm 21 (random coil)). 25,41,42,[47][48][49][50] Furthermore, the intense vibration at 935 cm 21 confirms the predominance of the a-helix conformation. These results agree with the previous studies about the evaluation of the secondary conformations of the epidermis.…”

“…These results agree with the previous studies about the evaluation of the secondary conformations of the epidermis. 25,29,[47][48][49][50][51] Lipids of the Episkin Model. The lipids of the epidermis are mainly constituted of ceramides, cholesterol, fatty acids, and membrane phospholipids of cells.…”

Analysis of internal structure changes in black human hair keratin fibers with aging using Raman spectroscopy

“…The direct characterization of keratin fibers has been performed using X-ray diffraction, 1,[7][8][9][10][11][12] solid state NMR, 8,13 Raman, [14][15][16][17][18][19][20][21][22][23][24][25][26][27][28] and Infrared spectroscopy. 14,16,17 Information about the amorphous region (the cuticle and matrix) of…”

“…On the other hand, when directly characterizing the cuticle and cortex structure of a single keratin fiber, the analytical technique using a Raman microscope is effective as it can be measured at a spot diameter of 1 lm. [20][21][22][23][24][25][26] Most importantly, by using this method, information about the crystalline fibrous (microfibril) and amorphous (matrix) structures existing in the cortex region can be obtained. However, up to now, Raman spectroscopic analysis had been limited to white human hair, [20][21][22][23][24][25][26] which has no melanin granules, and blond human hair, 27,28 which has few melanin granules.…”