Isomeric cysteinyldopas provide a (photo)degradable bulk component and a robust structural element in red human hair pheomelanin
Isomeric cysteinyldopas provide a (photo)degradable bulk component and a robust structural element in red human hair pheomelanin
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DOI：
10.1111/j.1755-148x.2009.00561.x
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发表时间：
2009-06-01
影响因子：
4.3
通讯作者：
d'Ischia, Marco
中科院分区：
文献类型：
--
作者：
Greco, Giorgia;Wakamatsu, Kazumasa;d'Ischia, Marco
碱性H2O2降解红发褐黑素，除得到6-（2-氨基-2-羧基乙基）-2-羧基-4-羟基苯并噻唑（BTCA）外，还得到一个新产物，该产物经鉴定为7-（2-氨基-2-羧基乙基）-2-羧基-4-羟基苯并噻唑（BTCA-2），来源于2- s -半胱氨酸多巴（2SCD）衍生物。BTCA-2也可从多种黑色素组织和合成色素中获得。在一组19个人中，对距离头皮不同距离的红发进行BTCA和BTCA-2的同时测定表明，从发根到发梢的BTCA产量突然下降，而BTCA-2的值在整个头发长度中几乎保持不变。4-氨基-3-羟基苯基丙氨酸（AHP）和3-氨基酪氨酸（AT）在同一锁段的分析结果也显示出相似的趋势，而噻唑-2,4,5-三羧酸（TTCA）的产率则随着离头皮距离的增加而增加。头发长时间暴露在阳光下会导致BTCA-显著减少，但产生BTCA-2的元素不会。最后，模型研究表明，在体外合成黑色素的过程中，5SCD-而不是2scd -衍生单位的大量降解。结果表明，红发现象黑色素由可降解的5scd衍生体组成，并与稳定的2scd衍生单位相关。头发生长过程中发生的结构退化可能是部分与阳光照射有关的氧化过程的结果。
Alkaline H2O2 degradation of red hair pheomelanin gave, besides 6-(2-amino-2-carboxyethyl)-2-carboxy-4-hydroxybenzothiazole (BTCA), a new product which was identified as 7-(2-amino-2-carboxyethyl)-2-carboxy-4-hydroxybenzothiazole (BTCA-2) originating from 2-S-cysteinyldopa (2SCD) derived units. BTCA-2 was also obtained from a variety of pheomelanic tissues and synthetic pigments. Simultaneous determination of BTCA and BTCA-2 in segments of red hair locks taken at variable distances from the scalp in a group of 19 individuals indicated an abrupt drop of BTCA yields on passing from root to tip, whereas BTCA-2 values remained virtually constant throughout hair length. Analysis of 4-amino-3-hydroxyphenylalanine (AHP) and 3-aminotyrosine (AT) in the same lock segments showed a closely similar trend, whereas yields of thiazole-2,4,5-tricarboxylic acid (TTCA) increased with increasing the distance from the scalp. Prolonged exposure of hair locks to sunlight caused a significant decrease in BTCA-, but not BTCA-2-yielding elements. Finally, model studies showed a substantial degradation of 5SCD-, but not 2SCD-derived units, during pheomelanin synthesis in vitro. It is concluded that red hair pheomelanin consists of a degradable 5SCD-derived bulk component associated with stable 2SCD-derived units. Structural degradation occurs during hair growth probably as a result of oxidative processes related in part to sun exposure.