Innovative Beauty Science Laboratory, Kanebo Cosmetics Inc., Kotobuki-cho, Odawara-shi, Kanagawa, Japan.
J Xray Sci Technol. 2011;19(3):313-20. doi: 10.3233/XST-2011-0295.
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.
人类毛发纤维主要由角蛋白组成，其特点是半胱氨酸含量非常高，半胱氨酸是一种含硫氨基酸，通常通过二硫键形成胱氨酸。众所周知，在烫发或染发过程中，一些胱氨酸残基会转化为半胱氨酸磺酸，尽管其分布和程度的细节尚不清楚。在这项研究中，通过使用 S-K 吸收边胱氨酸和半胱氨酸磺酸的 XANES 谱的差异，证实了匀浆处理的烫发或漂白头发样品中半胱氨酸磺酸的形成。此外，还使用 X 射线接触显微镜对毛发切片样品进行了半胱氨酸磺酸的化学绘图。与其他部位相比，漂白头发的表皮层（毛鳞片）显示出最高的半胱氨酸磺酸含量，而烫发头发则显示出相对均匀的分布。这一发现表明，烫发和漂白以不同的机制损伤头发。
