Kouji Takehara’s scientific contributions

In recent years, hair damage by sunlight and chemical treatment such as perming and bleaching has become a consumer concern. It is important to understand the effect of sunlight and chemical treatment on hair microstructure to develop the technology for protection and repair of hair. Our previous study demonstrated that a differential phase contrast scanning X-ray microscopy was a useful nondestructive analysis method to observe internal hair structure with high-resolution. In this study, hair samples with three different chemical treatment (normal, perming and bleaching) and additional irradiation by artificial sunlight were observed with a scanning X-ray microscopic tomography system using a synchrotron radiation light source in order to understand the damaging effect of both sunlight and chemical treatment on hair. The porosity rate in the cortex is higher in the permed hair than normal hair and void distribution in the cross section of permed hair is localized. The porosity rate in the cortex of permed hair is decreased by additional irradiation. The porosity rate of bleached hair is the same as that of normal hair and isn't changed by the irradiation. These results suggest that hair microstructural change in the cortex by sunlight is affected by the prior chemical treatments, and development of varied protection and repair technology depending on the prior treatment situation is needed.

Human hair fibers are primarily composed of keratin protein, characterized by a very high content of cysteine, a sulfur-containing amino acid, which ordinarily forms cystine via a disulfide bond. It is known that some cystine residues are converted to cysteic acid during permanent waving or hair coloring, although details of their distribution and extent are still unclear. In this study, by using difference in XANES profiles of cystine and cysteic acid at the S-K absorption edge, the formation of cysteic acid was confirmed for homogenized samples of permed or bleached hair. Furthermore chemical mapping of cysteic acid was performed on hair-section samples with X-ray contact microscopy. The peripheral region, cuticle, in bleached hair showed the highest content of cysteic acid compared with the other parts, while permed hair showed relatively uniform distribution. This finding suggests that perming and bleaching damage hair by different mechanisms.

Human hair fibers are primarily composed of keratin protein, characterized by a very high content of cysteine, a sulfur-containing amino acid, which ordinarily forms cystine via a disulfide bond. It is known that some cystine residues are converted to cysteic acid during permanent waving or hair coloring, although details of their distribution and extent are still unclear. In this study, by using difference in XANES profiles of cystine and cysteic acid at the S-K absorption edge, the formation of cysteic acid was confirmed for homogenized samples of permed or bleached hair. Furthermore chemical mapping of cysteic acid was performed on hair-section samples with X-ray contact microscopy. The peripheral region, cuticle, in bleached hair showed the highest content of cysteic acid compared with the other parts, while permed hair showed relatively uniform distribution. This finding suggests that perming and bleaching damage hair by different mechanisms.

XANES spectra of biomacromolecules such as histone, hemoglobin or bovine serum albumin (BSA) were measured in transmission at the S-K absorption edge for comparison with those of sulfur containing low-molecular weight biomolecules with special reference to the dependence on the chemical environment of sulfur. The spectra of dry histone and hemoglobin exhibited a prominent peak at the same energy as that of cysteine and glutathione (GSH), while the BSA spectrum showed an additional peak at a lower energy, which coincided with that of cystine and glutathione disulfide (GSSG). XANES peaks were found at the same energy even in a mammalian cell dry pellet. Spectra in the hydrated state exhibited similar profiles except for a very slight shift of resonance peaks to the lower energy. These results indicate that XANES profiles could be applicable to the mapping of S-C and S-S bonds in dry/hydrated biological systems using a spectromicroscopic technique. In addition, mass absorption coefficients of GSH and GSSG were determined.

XANES spectra of biomacromolecules such as histone, hemoglobin or bovine serum albumin (BSA) were measured in transmission at the S-K absorption edge for comparison with those of sulfur containing low-molecular weight biomolecules with special reference to the dependence on the chemical environment of sulfur. The spectra of dry histone and hemoglobin exhibited a prominent peak at the same energy as that of cysteine and glutathione (GSH), while the BSA spectrum showed an additional peak at a lower energy, which coincided with that of cystine and glutathione disulfide (GSSG). XANES peaks were found at the same energy even in a mammalian cell dry pellet. Spectra in the hydrated state exhibited similar profiles except for a very slight shift of resonance peaks to the lower energy. These results indicate that XANES profiles could be applicable to the mapping of S-C and S-S bonds in dry/hydrated biological systems using a spectromicroscopic technique. In addition, mass absorption coefficients of GSH and GSSG were determined.