Magnetic investigations of human mesencephalic neuromelanin
Magnetic investigations of human mesencephalic neuromelanin
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DOI：
10.1016/s0925-4439(01)00099-0
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发表时间：
2002-03-16
影响因子：
6.2
通讯作者：
Crippa, PR
中科院分区：
文献类型：
--
作者：
Bolzoni, F;Giraudo, S;Crippa, PR
黑质神经元的色素沉着是由于神经黑色素，一种储存大量铁的色素。本文用磁化率法研究了人中脑神经黑色素随温度的变化。磁性测量提供了埋在有机黑色素基质中的铁簇的物理化学表征，并支持铁不是简单地螯合，而是组织在三维网络中的观点。孤立的铁离子的顺磁性观察，与电子顺磁共振谱。此外，反铁磁颗粒具有大的尺寸分布函数。这些晶粒包含N个反铁磁耦合的自旋;然而，N-1/2自旋与晶粒体解耦并平行排列。后者的亚晶粒是超顺磁性的阻断温度范围在5 K和室温之间。在合成黑色素中没有观察到这种行为，其中顺磁贡献强烈增强。从受帕金森病影响的患者中分离的色素的初步结果显示，与对照神经黑色素相比，总磁化强度较低，帕金森病是一种主要涉及黑质神经元的神经退行性病变。零场冷却和场冷却磁化的温度行为对于两者是相似的。帕金森氏病神经黑色素中铁含量的显著减少可能表明铁从其储存介质向胞质溶胶的进行性迁移。(C)2002 Elsevier Science B. V.保留所有权利。
Pigmentation of neurons in substantia nigra is due to neuromelanin, a pigment that stores large amounts of iron. Human mesencephalic neuromelanin has been investigated by means of magnetic susceptibility measurements as 1 function of temperature. Magnetic measurements provide a physico-chemical characterization of the iron cluster buried in the organic melanin matrix and support the view that iron is not simply chelated, but rather is organized in a three-dimensional network. The paramagnetism of isolated iron ions is observed, in agreement with electron paramagnetic resonance spectroscopy. Furthermore, antiferromagnetic grains with a large size distribution function are present. These grains contain N spins coupled antiferromagnetically; however, N-1/2 spins are decoupled from the grain bulk and parallelly aligned. The latter subgrains are superparamagnetic with a blocking temperature ranging between 5 K and room temperature. This behavior has not been observed in synthetic melanin, where the paramagnetic contribution is strongly enhanced. Preliminary results on pigment isolated from patients affected by Parkinson's disease, a neurodegenerative pathology involving primarily pigmented neurons in substantia nigra pars compacta, show a lower total magnetization compared to control neuromelanin. The temperature behavior of zero field cooling and field cooling magnetizations is similar for both. The significant depletion of iron content in Parkinson's disease neuromelanin could indicate a progressive Fe migration from its storage environinent to the cytosol. (C) 2002 Elsevier Science B.V. All rights reserved.