Neuromelanins Isolated from Different Regions of the Human Brain Exhibit a Common Surface Photoionization Threshold
Neuromelanins Isolated from Different Regions of the Human Brain Exhibit a Common Surface Photoionization Threshold
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DOI：
10.1111/j.1751-1097.2008.00476.x
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发表时间：
2009-01-01
影响因子：
3.3
通讯作者：
Simon, John D.
中科院分区：
文献类型：
--
作者：
Bush, William D.;Garguilo, Jacob;Simon, John D.
通过扫描探针和光电子发射显微镜研究从人脑的前运动皮层、小脑、壳核、苍白球和胼胝体中分离出的神经黑色素，并将结果与之前发表的关于黑质神经黑色素的研究进行比较。扫描电子显微镜揭示了所有神经黑色素的共同结构。所有这些都呈现出直径在 200 至 400 nm 之间的球形实体，由直径类似于 30 nm 的较小球形子结构组成。这些特征与在许多黑色素系统中观察到的特征相似，包括乌贼、牛眼、人眼和头发黑素体。使用杜克自由电子激光器的自发发射输出，在 248 至 413 nm 之间的特定紫外线波长下收集所有神经黑色素的光电子显微镜图像。数据分析确定了神经黑色素的共同阈值光电离电位为 4.7 +/- 0.2 eV，对应于正常氢电极 (NHE) 的 -0.3 +/- 0.2 V 氧化电位。这些结果与之前报道的黑质神经黑色素的潜力一致，为 4.5 +/- 0.2 eV（-0.1 +/- 0.2 V vs NHE）。所有神经黑色素都表现出共同的低表面氧化电位，反映了它们的真黑色成分以及它们无法触发具有神经毒性作用的氧化还原过程。
Neuromelanin isolated from the premotor cortex, cerebellum, putamen, globus pallidus and corpus callosum of the human brain is studied by scanning probe and photoelectron emission microscopies and the results are compared with previously published work on neuromelanin from the substantia nigra. Scanning electron microscopy reveals common structure for all neuromelanins. All exhibit spherical entities of diameters between 200 and 400 nm, composed of smaller spherical substructures, similar to 30 nm in diameter. These features are similar to that observed for many melanin systems including Sepia cuttlefish, bovine eye, and human eye and hair melanosomes. Photoelectron microscopy images were collected for all neuromelanins at specific wavelengths of ultraviolet light between 248 and 413 nm, using the spontaneous emission output from the Duke free electron laser. Analysis of the data establishes a common threshold photoionization potential for neuromelanins of 4.7 +/- 0.2 eV, corresponding to an oxidation potential of -0.3 +/- 0.2 V vs the normal hydrogen electrode (NHE). These results are consistent with previously reported potentials for neuromelanin from the substantia nigra of 4.5 +/- 0.2 eV (-0.1 +/- 0.2 V vs NHE). All neuromelanins exhibit a common low surface oxidation potential, reflecting their eumelanic component and their inability to trigger redox processes with neurotoxic effect.