Liu Yan, Kempf Valerie R, Nofsinger J Brian, Weinert Emily E, Rudnicki Mark, Wakamatsu Kazumasa, Ito Shosuke, Simon John D
Department of Chemistry, Duke University, Durham, NC 27708, USA.
Pigment Cell Res. 2003 Aug;16(4):355-65. doi: 10.1034/j.1600-0749.2003.00059.x.
Eumelanin was isolated from a sample of black, Indonesian human hair using three different published procedures: two different acid/base extractions and an enzymatic extraction. The morphology and spectroscopic properties of the isolated pigments differ significantly. The acid/base procedures both yield an amorphous material, while enzymatic extraction yields ellipsoidal melanosomes. Amino acid analysis shows that there is protein associated with the isolated pigments, accounting for 52, 40 and 14% of the total mass for the two acid/base extractions and the enzymatic extraction, respectively. The amino acid compositions do not correlate with those of keratin or tyrosinase. Metal elemental analysis shows that the acid/base extraction removes a majority of many metal ions bound to the pigment. Chemical degradation analysis by KMnO4/H+ and H2O2/OH- indicates significant differences between the pigments isolated by acid/base and enzymatic extraction. After correction for the protein mass in the two pigments, the lower yields of both pyrrole-2,3,5-tricarboxylic acid and pyrrole-2,3-dicarboxylic acid, eumelanin degradation products, indicate acid/base extraction modifies the chemical structure of the melanin, consistent with the result of Soluene solubilization assay. While the optical absorption spectra of the bulk pigments are similar, the spectra of the molecular weight less than 1000 mass fractions differ significantly. The data clearly indicate that pigment obtained from human hair by acid/base extraction contains significant protein, exhibits destruction of the melanosome, and possesses altered molecular structure. The acid/base extracted hair melanin is not representative of the natural material and is a poor model system for studying the physical and biological properties of melanins. The enzymatically extracted hair melanin, on the contrary, retains the morphology of intact melanosomes and is an excellent source of human melanin.
两种不同的酸碱提取法和一种酶提取法。分离出的色素的形态和光谱特性有显著差异。酸碱提取法均产生无定形物质，而酶提取法产生椭圆形黑素小体。氨基酸分析表明，分离出的色素与蛋白质相关，在两种酸碱提取法和酶提取法中，蛋白质分别占总质量的52%、40%和14%。氨基酸组成与角蛋白或酪氨酸酶的氨基酸组成不相关。金属元素分析表明，酸碱提取法去除了与色素结合的大多数金属离子。用KMnO4/H+和H2O2/OH-进行的化学降解分析表明，酸碱提取法和酶提取法分离出的色素之间存在显著差异。在对两种色素中的蛋白质质量进行校正后，真黑素降解产物吡咯-2,3,5-三羧酸和吡咯-2,3-二羧酸的产率较低，这表明酸碱提取法改变了黑色素的化学结构，这与Soluene溶解试验的结果一致。虽然整体色素的光吸收光谱相似，但分子量小于1000质量分数的光谱有显著差异。数据清楚地表明，通过酸碱提取法从人发中获得的色素含有大量蛋白质，黑素小体遭到破坏，分子结构发生改变。酸碱提取的毛发黑色素不能代表天然物质，是研究黑色素物理和生物学特性的不良模型系统。相反，酶提取的毛发黑色素保留了完整黑素小体的形态，是人类黑色素的优良来源。
