Elucidation of the hierarchical structure of natural eumelanins
Elucidation of the hierarchical structure of natural eumelanins
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DOI：
10.1098/rsif.2018.0045
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发表时间：
2018-03
影响因子：
3.9
通讯作者：
Ming Xiao;Wei Chen;Weiyao Li;Jiuzhou Zhao;You-lee Hong;Y. Nishiyama;Toshikazu Miyoshi;M. Shawkey;A. Dhinojwala
中科院分区：
文献类型：
--
作者：
Ming Xiao;Wei Chen;Weiyao Li;Jiuzhou Zhao;You-lee Hong;Y. Nishiyama;Toshikazu Miyoshi;M. Shawkey;A. Dhinojwala
真黑素是生物体中最普遍的色素之一，在着色和防紫外线方面发挥着重要作用。由于真黑素是高度交联的，不溶于溶剂，其化学结构仍不完全清楚。在这项研究中，我们使用原子力显微镜、X射线光电子能谱和固体核磁共振(核磁共振)对四个系统发育上相距较远的物种完整的真核糖体(色素颗粒主要由真黑蛋白组成)进行了比较：乌贼(乌贼)墨水、乌鸦(乌鸦)羽毛、彩虹野生火鸡(Melleagris Gallopavo)羽毛和人类黑色头发。我们发现，所有四个物种的真核糖体都由长度为10-60 nm的亚单位纳米颗粒组成，这与先前从乌贼墨水和人类头发中观察到的真黑素小体的情况一致。固体核磁共振结果表明，在所有四种真黑素中都存在苯醌甲基互变异构体。我们还发现乌贼的紫外光吸光度、5，6-二羟基吲哚-2-羧酸/5，6-二羟基吲哚的比值和质子化芳基碳的比值与其他三种物质有明显的差异。这种在系统发育上广泛的生物群体中天然真黑素的比较提供了对真黑素结构在进化历史上的变化的洞察力，并使合成真黑素具有与天然真黑素相似的性质成为可能。
Eumelanin is one of the most ubiquitous pigments in living organisms and plays an important role in coloration and UV protection. Because eumelanin is highly cross-linked and insoluble in solvents, the chemical structure is still not completely known. In this study, we used atomic force microscopy, X-ray photoelectron spectroscopy and solid-state nuclear magnetic resonance (NMR) to compare intact eumelanosomes (pigment granules mostly made of eumelanin) from four phylogentically distant species: cuttlefish (Sepia officinalis) inks, black fish crow (Corvus ossifragus) feathers, iridescent wild turkey (Melleagris gallopavo) feathers and black human hair. We found that eumelanosomes from all four species are composed of subunit nanoparticles with a length of 10–60 nm, consistent with earlier observations in eumelanosomes from the sepia ink and human hair. The solid-state NMR results indicate the presence of quinone methide tautomers in all four eumelanins. We also found clear differences in the UV absorbance, the ratio of 5,6-dihydroxyindole-2-carboxylic acid/5,6-dihydroxyindole and protonated aryl carbon ratios in sepia eumelanin relative to the other three. This comparison of natural eumelanin across a phylogenetically broad group of organisms provides insights into the change in the eumelanin structure over the evolutionary history and enables the production of synthetic eumelanin with properties that are similar to natural eumelanin.